(2021) 7:64
Prochilo et al. Pilot and Feasibility Studies
https://doi.org/10.1186/s40814-020-00751-6
RESEA RCH
Open Access
A 16-week aerobic exercise and
mindfulness-based intervention on chronic
psychosocial stress: a pilot and feasibility
study
Guy A. Prochilo1,2*
, Ricardo J.S. Costa3 , Craig Hassed4 , Richard Chambers5 and Pascal Molenberghs2
Abstract
Objectives: Researchers have begun delivering mindfulness and aerobic exercise training concurrently on the
premise that a combination intervention will yield salutary outcomes over and above each intervention alone. An
estimate of the effect of combination training on chronic psychosocial stress in a nonclinical population has not been
established. The objective of this study was to establish protocol feasibility in preparation of a definitive RCT targeting
healthy individuals, and to explore the preliminary effect of combination training on reducing chronic psychosocial
stress in this population.
Methods: Twenty-four participants were allocated to a single-arm pre-post study and subjected to 16 weeks of
concurrent mindfulness psychoeducation and aerobic exercise training. Feasibility criteria were collected and
evaluated. Within-group changes in chronic psychosocial stress, mindfulness, emotion regulation, and
cardiorespiratory fitness were also assessed. Primary analyses were based on 17 participants.
Results: Retention rate, response rate, recruitment rate, and sample size analyses indicate a definitive trial is feasible
for detecting most effects with precision. There was also a decline in our primary dependent measure of chronic
psychosocial stress (dpretest = −0.56, 95% CI [−1.14, −0.06]). With regard to secondary measures, there was an increase
in the use of cognitive reappraisal, and a reduction in use of maladaptive emotion regulation
strategies.
We are
insufficiently confident to comment on changes in mindfulness and aerobic capacity V̇O2max . However, there were
subgroup improvements in aerobic economy at submaximal exercise intensities.
Conclusions: We recommend a definitive trial is feasible and should proceed.
Trial registration: ANZCTR (ID: ACTRN12619001726145). Retrospectively registered December 9, 2019.
Keywords: Pilot and feasibility study, Aerobic exercise, Mindfulness, Mental and physical training, Nonclinical sample
*Correspondence: guy.prochilo@gmail.com
Melbourne School of Psychological Sciences, University of Melbourne,
Melbourne, Australia
2
ISN Psychology, Institute for Social Neuroscience, Melbourne, Australia
Full list of author information is available at the end of the article
1
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Prochilo et al. Pilot and Feasibility Studies
(2021) 7:64
Background
A growing body of research has implicated psychosocial stress with a range of deleterious health outcomes.
At an individual level, this includes a greater incidence
of depressive symptoms, anxiety, and a decline in wellbeing [1, 2], as well as impairments of physical health
[3, 4]. To address these problems, interventions involving aerobic exercise [5] and mindfulness [6] have been
found effective for improving mental health outcomes.
Given these benefits, researchers have also begun delivering these interventions concurrently [7]. The rationale for
a combination training modality is that such training may
yield salutary outcomes over and above each intervention
alone [8].
Few studies have examined the effect of combining
aerobic exercise and mindfulness-based training on mental health outcomes. To our knowledge, an estimate of
the range and direction of the effect of a combination
intervention on chronic psychosocial stress in a nonclinical population, specifically, is also absent from the
literature. This pilot and feasibility study was conducted
to guide future research on combination training with
respect to its effect on chronic psychosocial stress, as well
as its potential mechanisms. To this end, we conducted
a single-arm pre-post study in preparation for a future
randomized controlled trial (RCT). This study comprised
an aerobic exercise and mindfulness-based intervention
delivered concurrently over 16 weeks, and was designed
as a prevention-focused intervention to be used by healthy
individuals rather than those presenting with specific
mental health risk factors. In the following sections, we
discuss the evidence and theorized mechanisms that link
mindfulness, aerobic exercise, and combination training
to salutary mental health outcomes. We conclude with our
study rationale.
Page 2 of 17
ing the attention to spend more time in the present
moment [13].
Meta-analysis of controlled trials suggests that MBIs
may improve multiple indices of mental health (here
reported as the between-group standardized mean
difference, d, reported in each publication). This
includes a reduction in psychosocial stress (d = −0.74,
95% CI [−1.07, −.41]), anxiety (d = −0.64, 95% CI
[−.94, −.33]), and depressive symptoms (d = −0.80, 95%
CI [−1.12, −.49]) [6]. There also appears to be a doseresponse relationship between formal meditation practice
and salutary mental health outcomes (r = .26) [14]. However, the relationship between the overall duration of an
MBI and these outcomes remains equivocal [6].
The cognitive and emotional mechanisms by which
MBIs exert their effects on mental health have been
assessed through a meta-analysis of intervention studies
using mediation models [15]. These authors applied a best
evidence synthesis rating system (BESRS) to determine
if a body of evidence was considered strong, moderate,
or insufficient [16]. They reported strong evidence for
reduced cognitive and emotional reactivity, and moderate evidence for dispositional mindfulness and repetitive
negative thinking as predictors of improvement in mental
health (pooled correlations: rs = .33 to .36). These mechanisms are additionally captured by mindfulness theories.
For example, the mindfulness-to-meaning theory suggests
that mindfulness may help individuals select more adaptive emotion regulation strategies in times of stress, and
thereby reduce reactivity to stressful events [17]. Particular interest is given to cognitive reappraisal, which
is a strategy that involves actively reinterpreting emotional stimuli to modify its emotion impact. Cognitive
reappraisal is considered a central mechanism in some
mindfulness theories [17], although is a secondary effect
in others [18].
Mindfulness
Mindfulness is a mental practice that draws on contemplative traditions and evidence-based research, and
which has been adopted as a therapeutic approach
to promote mental and physical health [9]. In a
clinical and research context, mindfulness has been
described as a non-judgmental, non-reactive, and nonelaborative attention to the present moment experience, and is an innate capacity that can be strengthened through formal meditation and informal practice
[10]. Mindfulness-based interventions (MBIs) have proliferated, and include Mindfulness-based Stress Reduction [11] and Mindfulness-based Cognitive Therapy [12],
among others. MBIs vary widely in their focus, content,
and structure. However, the formal features that define
an MBI are inclusion of (1) systematic and sustained
training in formal meditation and informal practices, and
(2) an underlying theoretical model based around train-
Aerobic exercise
Physical activity is a broad term that applies to any bodily
movement or activity produced by skeletal muscles that
require energy expenditure [19]. Aerobic exercise is a specific subcategory of physical activity that is characterized
by rhythmic, sustained movement of large muscle groups,
and which is primarily dependent on energy-generating
processes that occur through oxygen metabolism. The primary goal of aerobic exercise is to improve or maintain
cardiorespiratory fitness, which is the capacity of the circulatory and respiratory system to supply oxygen during
sustained exercise.
Aerobic exercise is the most widely examined exercise
modality with respect to mental health outcomes, and
there is sufficient evidence to suggest it is implicated
in improvements in psychological health. For example,
meta-analyses of RCT interventions show that aerobic
Prochilo et al. Pilot and Feasibility Studies
(2021) 7:64
exercises of various modalities are capable of reducing
depressive symptoms (d = −0.55, 95% CI [−0.77, −0.34])
[5] and anxiety symptoms (d = −0.58, 95% CI [−1.0 to
−0.76]) [20]. There is also meta-analytic evidence that
the effect of aerobic exercise on mental health outcomes
may follow a dose-response relationship with the number of exercise sessions completed (although effect size
may decline in magnitude at very high frequencies, e.g.,
37+ exercise sessions) [5]. Meanwhile, the relationship
between effect size and intensity of exercise has not yet
been established [5, 21].
Aerobic exercise can be implicated in improvement
in cardiorespiratory fitness, which in turn is associated
with widespread physiological effects that enhance cardiovascular health. For example, this includes improved
glucose tolerance, reduced low-grade chronic inflammation, and a lower prevalence of hypertension [22].
With respect to psychosocial stress, it has been hypothesized that the salutary mental health outcomes that arise
following exercise training may be related to exerciseassociated adaptations to stress-responsive systems [23].
This includes a reduction in reactivity of cardiovascular, metabolic, autonomic, and neuroendocrine systems in response to exercise stress, which carry over
to a reduction in reactivity in response to psychosocial stressors. Consequently, cardiorespiratory fitness may
be an important mediator of improvements in mental health outcomes observed following regular aerobic
exercise.
Self-reports of physical activity are a subjective construct that measure behaviors that may be associated
with cardiorespiratory fitness. These constructs are often
implicated in a reduction in psychosocial stress and the
prevalence of stress-related disorders [24, 25]. However,
direct assessments of cardiorespiratory fitness provide a
more objective method of investigating the relationship
between fitness and mental health.
In the exercise physiology literature, two objectivemeasures include maximal aerobic capacity V̇ O2max and
aerobic economy [26, 27]. V̇ O2max represents the maximal amount of oxygen that can be consumed during
exhaustive exercise, where a higher V̇ O2max is indicative
of greater cardiorespiratory fitness. Aerobic economy represents the steady-state energy requirement of exercise
conducted at a constant exercise intensity (e.g., running at
a constant velocity). Here, a lower energy requirement at a
constant intensity is indicative of higher aerobic economy
and greater cardiorespiratory fitness. Research examining the relationship between V̇ O2max and mental health
outcomes has so far been mixed. Several cross-sectional
studies have reported no relationship between V̇ O2max
and mental health [28, 29], while a recent controlled trial
reported that an improvement in V̇ O2max was associated
with a reduction in psychosocial stress [30]. Meanwhile,
Page 3 of 17
aerobic economy is relatively understudied in the mental
health literature altogether.
Combination training
Improvements in mental health outcomes are often
observed in interventions that make use of mindfulness
in combination with physical activity [11]. One recent
example is Mindful2Work: a single-arm pilot and feasibility study that delivered mindfulness, physical activity,
and yoga training concurrently to a sample of employees medically diagnosed with severe work-related stress
[31]. This study comprised mindfulness psychoeducation
(80 min/week), home mindfulness practice (20 min/day),
physical activity (20 min twice per week), and yoga exercises (10 min twice per week) completed concurrently
over a period of 6 weeks. The authors reported that
participants declined in chronic psychosocial stress and
stress-related symptoms, and that these effects were also
maintained at a 6-week follow-up.
Unfortunately, such studies tend to examine physical
activity broadly, rather than through structured aerobic
exercise conducted at a frequency and intensity sufficient to maintain or improve cardiorespiratory fitness. For
example, in the above study, physical activity comprised
a combination of (unspecified) aerobic and strength exercises. The authors also relied on a subjective measure
of intensity (i.e., 70% of one’s full capacity) rather than
objective assessments via V̇ O2max .
One exception is mental and physical (MAP) training:
an intervention involving focused-attention meditation in
combination with aerobic exercise [7] (mode = treadmill
running or stationary cycling; intensity = heart rate equivalent to 50–70% V̇ O2peak ). Mental and physical training
components in this program were each conducted in separate 30-min sessions twice per week for 8 weeks. The
main outcomes of this study focused on pre-post changes
in depressive symptoms and the disposition to ruminate
separately in a group of clinically depressed and nondepressed participants. In this study, it was shown that
MAP training was successful in improving each of these
mental health outcomes in both groups, but decreases in
depressive symptoms were greater within the depressed
group than the non-depressed group. Moreover, there
were no reported changes in cardiorespiratory fitness for
any group of participants.
Rationale for a pilot and feasibility study
The above studies provide preliminary support that combining aerobic exercise and mindfulness-based training
may improve mental health outcomes. However, these
studies fall short of informing the development of a future
RCT as the basis for a prevention-focused stress reduction intervention in a nonclinical population. To this end,
we recruited a sample of healthy adults and conducted a
Prochilo et al. Pilot and Feasibility Studies
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single-arm pre-post pilot and feasibility study that comprised an aerobic exercise and mindfulness-based intervention that were completed concurrently over 16 weeks.
The aerobic exercise component, specifically, comprised
a mixture of endurance running and interval training
completed at a frequency and intensity considered sufficient to maintain or improve cardiorespiratory fitness
[32]. All comparisons performed in this study were pre-topost assessments. The primary research outcomes were
twofold. First, we aimed to obtain sufficient assurance of
protocol feasibility in a healthy population with respect
to retention rate, assessment response rate, recruitment
rate, and required sample size for a confirmatory trial.
And second, we aimed to obtain a preliminary estimate
of within-group changes in chronic psychosocial stress in
this population, as well as an estimate of change in secondary outcomes that may explain changes in chronic
psychosocial stress (i.e, mindfulness, emotion regulation
factors, and cardiorespiratory fitness).
Methods
Study design
This pilot and feasibility study was conducted as a singlearm pre-post study where all participants were subjected to aerobic exercise and mindfulness-based training,
delivered concurrently. Assuming that the relationship
between intervention exposure and its effect on psychosocial stress is linear, there will be greater statistical power to
detect within-group changes as the intervention duration
increases. Therefore, in this study, we doubled the typical duration of a mindfulness or MAP intervention and
subjected participants to 16 weeks of training.
This study was conducted across two waves: wave 1
(August to November 2016, n = 5) and wave 2 (April to
July 2017, n = 19). Recruitment was conducted across
a 1-month time period prior to the intervention period
of each wave. Pre-test (T0) and post-test (T1) measures
were obtained 1 to 4 weeks prior to and after the intervention period. Participants were predominantly postgraduate and undergraduate students from a variety of
disciplines, and these periods were selected to correspond
to low-stress periods in the academic calendar (i.e., preor post-semester). Responses to self-report measures were
collected online via Qualtrics (www.qualtrics.com), and
assessments of cardiorespiratory fitness were collected in
an exercise laboratory at Monash University. Descriptions
of each assessment are provided in the “Methods” section
below. No remuneration was offered.
Participants
Participants self-selected into the study by responding
to an advertisement posted to online community groups
based in Melbourne, Australia. These advertisements
described the study as a mental and physical training pro-
Page 4 of 17
gram for stress management. Young adults between the
ages of 18 and 35 years were targeted to reduce age-related
variance in assessment responses, and because this age
group was considered less likely to experience an adverse
exercise-related incident. Exclusion criteria were as follows: (1) age not within 18–35 years, (2) prior completion
of an endurance event equivalent to a half-marathon (21.1
km), (3) prior completion of a formal meditation program, (4) current diagnosis of a neurological or mental
disorder, (5) current diagnosis/history of chronic pain or
musculoskeletal conditions, (6) current diagnosis/history
of chronic disease of any kind, (7) current diagnosis
of a heat or cold disorder, (8) current use of medication that influences the neuroendocrine or immune system, (9) current injury of any kind (e.g., joint or muscle
injury), (10) current diagnosis of an infectious disease, (11)
BMI ≥ 30 kg/m2 , or (12) pregnancy or suspected pregnancy. All participants reported no engagement in regular
running training or meditation practice within 6 months
prior to the first assessment.
Pilot study methodologists suggest that 15–20 participants per cell of a pilot research design can provide a
reasonable estimate for most medium to large standardized effects as defined by Cohen [33], without wasting
resources [34]. To attain at least 15 participants and
account for an estimated dropout rate of 30–35%, the rule
for termination of data collection was set between 24 and
26 participants.
Intervention
The training program involved a mindfulness-based intervention (MBI) and aerobic exercise training program
completed concurrently over a period of 16 weeks. Each
component of the program is described in detail in
Supplementary Materials.
Briefly, the MBI comprised eight group psychoeducation and reflection activity sessions (55 min each) and formal focused-attention meditation practice (up to 20 min
of individual home practice, conducted daily). All group
training sessions followed a similar structure (Supplementary Materials Table 1) and were interspersed throughout
the full 16-week program (Supplementary Materials Table
2).
The exercise program comprised three runs per week
over 16 weeks following a half-marathon training schedule (Supplementary Materials Table 3), alongside several training support workshops. The exercise program
involved a combination of high-intensity interval training
and moderate-to-vigorous intensity endurance training,
with the latter gradually increasing in duration across
the intervention. Exercise intensity categories assigned
to each run were formally defined by the ACSM exercise prescription guidelines [32]. Participants differed in
cardiorespiratory fitness at baseline as identified through
Prochilo et al. Pilot and Feasibility Studies
(2021) 7:64
V̇ O2max testing. Therefore, exercise prescriptions adhering to these categories (i.e., the velocity required to
attain a specific intensity category) were individualized
to each participant by plotting oxygen consumption
(V̇ O2 mL/kg/min) against running velocity (km/h) in
a regression model derived from the baseline V̇ O2max
test. Participants were issued a GPS-enabled sportswatch
(Garmin Forerunner 235, Garmin, USA) to guide and
track their performance.
Adherence requirements for the MBI were that participants attend at least 50% of the group psychoeducation
sessions and complete at least 50% of the formal meditation target (target = 37.34 h 20 min/day over 16 weeks;
adherence requirement = 18.67 h). Compliance was monitored through attendance records and self-report of formal practice in an online spreadsheet (Google Sheets,
Google, USA). Adherence requirements for the exercise
program were that participants complete at least 50%
of all prescribed running sessions (target = 48 individual runs 3 runs/week over 16 weeks; adherence requirement = 24 runs). Additional measures of dosage included
total running distance (km), total running time (h), and
mean exercise intensity (reported as the mean percentage of V̇ O2max at which a participant conducted their
training averaged across all running sessions). Compliance was monitored through GPS-enabled sportswatch
data (i.e., running time, velocity, and distance) which was
recorded for each running session and uploaded to an
online database (http://connect.garmin.com).
Measures
Protocol feasibility
Retention rate
This measure was quantified as the percentage of participants allocated into this study who successfully completed
the study. A recent meta-analysis of MBIs for healthy
(i.e., nonclinical) individuals reported a mean dropout
rate of 17.0% [6]. However, this dropout rate ranged from
3.0 to 34.9% (65.1–97.0% retention) across studies. With
respect to aerobic exercise interventions, attrition rates in
previously non-exercising individuals have been reported
to range from 7 to 58% [35]. Based on this information, we determined that a retention rate as low as 65%
was an acceptable criterion to recommend proceeding
with a definitive trial. This corresponded to the lowest
retention rate reported for MBIs in healthy individuals.
Because MBIs typically have a high retention and have
been shown effective for reducing chronic psychosocial
stress, a retention lower than 65% may indicate that this
intervention is not feasible compared to already existing
effective interventions.
Page 5 of 17
data points across the study. An assessment response rate
of 95% for our primary dependent variable (chronic psychosocial stress) was considered an acceptable criterion to
recommend proceeding with a definitive trial.
Recruitment rate and sample size planning for a future
definitive trial
Recruitment rate was quantified as the percentage of all
applicants who satisfied the inclusion criteria and agreed
to participate. The required sample size was computed
for T1–T0 gain scores on the chronic psychosocial stress
measure (within-group changes), as well as for hypothetical differences between independent arms of a confirmatory trial (between-group changes) [33]. Recruitment and
sample size feasibility were assessed against a 5-year protocol where the 16-week program is repeated twice per
year for a total of 10 trials. A further assumption was made
that it would only be feasible to conduct each trial run
with a total 20 participants per treatment arm (i.e., with
four treatment arms: n = 80 per trial). This meant that
the total maximum number of participants across 10 trials
would be n = 200 per treatment arm (i.e., total N = 800).
Estimation of participant-centered outcomes
Chronic psychosocial stress
The Perceived Stress Scale (PSS-10) [33] was the primary
measure of chronic psychosocial stress and the primary
outcome measure for this study. The PSS-10 is one of the
most widely used psychosocial stress scales and assesses
the extent to which an individual appraises their life as
unpredictable, uncontrollable, or overloaded over the past
month (scale: 0 = never, 4 = very often). Higher total scores
on this 10-item measure reflect greater chronic psychosocial stress. The PSS-10 demonstrated good reliability in
this sample at pre-test (T0) and post-test (T1) (αT0 = .93;
αT1 = .80).
To provide converging evidence that changes in this
scale were reliable, we additionally assessed several secondary outcomes that should covary with PSS-10 scores.
This included depression, anxiety, and stress symptoms
using subscales of the Depression Anxiety Stress Scale
(DASS-21) [36], and subjective wellbeing using the World
Health Organization Wellbeing Index (WHO-5) [37].
Higher total scores on the DASS-21 represent poorer
mental health outcomes, while higher total scores on the
WHO-5 represent greater wellbeing. Each secondary outcome measure demonstrated adequate reliability at each
time point (DASS-21: depression αT0 = .87, αT1 = .79;
anxiety αT0 = .64, αT1 = .81; stress αT0 = .64, αT1 = .73;
WHO-5: wellbeing αT0 = .86, αT1 = .83).
Assessment response rate
Dispositional mindfulness
This measure was quantified as the percentage of participants providing full pre-test (T0) and post-test (T1)
The Mindful Attention Awareness Scale (MAAS) [38]
was used to assess dispositional use of mindfulness. The
Prochilo et al. Pilot and Feasibility Studies
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MAAS is a widely used 15-item scale that examines how
frequently individuals experience an absence of attention
to and awareness of present moment experiences (scale:
1 = almost always, 6 = almost never). Higher mean scores
indicate higher dispositional mindfulness. The MAAS
demonstrated good reliability in this sample (αT0 = .86;
αT1 = .85).
Cognitive reappraisal
The cognitive reappraisal subscale of the Emotion Regulation Questionnaire (ERQ-CR) [39] was used to assess
dispositional use of cognitive reappraisal. This 6-item
scale assesses the extent to which an individual uses cognitive reframing of situations to change how they feel about
an emotional experience (scale: 1 = strongly disagree,
7 = strongly agree). Higher mean scores indicate higher
dispositional use of cognitive reappraisal. The ERQ-CR
had good reliability (αT0 = .91; αT1 = .93).
Repetitive negative thinking
Maladaptive rumination (past-oriented) and worry
(future-oriented) were used to assess the disposition
to engage in self-focused, repetitive, and perseverative
thought processes that maintain negative affect during
times of psychosocial stress (i.e., maladaptive emotion
regulation strategies).
The maladaptive form of rumination was examined
using the 5-item brooding subscale of the Ruminative
Responses Scale (RRS-BR) [40], where higher scores
indicate greater use of negative self-reflection and a
focus on obstacles to problems when experiencing a
negative mood (scale: 1 = almost never, 4 = almost
always). The reflection subscale of this scale was excluded
because it captures positive aspects of rumination and
has been shown to suffer from a poor factor structure
[41]. The RRS-BR had good reliability (αT0 = .88; αT1
= .86). Worry was examined using the 16-item Penn
State Worry Questionnaire (PSWQ) [42]. The PSWQ
assesses the generality, excessiveness, and uncontrollability and an individuals’ disposition to worry (scale: 1
= not at all typical of me, 5 = very typical of me).
Higher total scores indicate a higher disposition to
worry. The PSWQ had good reliability in this sample
(αT0 = .96; αT1 = .91).
Cardiorespiratory fitness
Maximal aerobic capacity V̇ O2max and aerobic economy were estimated using a graded incremental exercise
protocol on a motorized treadmill [43]. During the exercise protocol, a 1% treadmill gradient was maintained to
match the energy-cost of outdoor running [44]. Prior to
beginning the protocol, participants completed a 2–3-min
warm-up of treadmill running at a low-intensity velocity
of their choosing. The protocol began with treadmill running at 6 km/h, and velocity (i.e., exercise intensity) was
Page 6 of 17
increased in increments of 2 km/h every 3 min until volitional exhaustion or until V̇ O2max criteria were obtained.
The final minute of treadmill running at each velocity (i.e., 2 to 3 min) represented the steady-state for a
given exercise intensity (e.g., 6, 8, 10, 12, and 14 km/h). At
each steady-state period, heart rate was recorded using a
Polar heart rate monitor (Polar Electro, Kempele, Finland)
and perceived exertion was recorded using the Borg Rating of Perceived Exertion (RPE) scale [45]. Oxygen consumption (V̇ O2 L/min) was measured continuously using
open-circuit spirometry (Vmax Encore Metabolic Cart,
Carefusion, San Diego, CA, USA). Criteria for V̇ O2max
were volitional exhaustion, or when two of the following were satisfied: (1) a plateau in oxygen consumption
despite increasing work rate, (2) a heart rate more than
90% predicted (220 beats/min minus age in years), or (3) a
respiratory exchange ratio greater than 1.15.
Four measures of aerobic economy were obtained in the
final minute of each running velocity (i.e., each steadystate exercise intensity). This included (1) absolute oxygen
cost (V̇ O2 L/min), (2) relative oxygen cost (i.e., oxygen cost relative to V̇ O2max ; %V̇ O2max ), (3) heart rate
(beats/min), and perceived exertion (RPE). The percentage of participants reaching each intensity were as follows:
6 km/h = 100%, 8 km/h = 100%, 10 km/h = 82.4%, 12 km/h
= 76.5%, and 14 km/h = 23.5%. Therefore, to assess withingroup changes in aerobic economy with respect to time
and across the broadest range of exercise intensities, analyses of aerobic economy were restricted to the 76.5% of
participants with full data across 6 to 12 km/h (i.e., n = 13).
To ensure test-retest reliability, testing protocols at T0
and T1 were conducted under identical conditions (temperature, 20–25 ◦ C; humidity, ≤ 60%; air circulation controlled at 10 km/h using a motorized fan; assessments at
T0 and T1 were completed at the same time within ± 2
h). Participants were prohibited exercise, alcohol, or caffeine consumption within 24 h of testing, and diet was
restricted (i.e., mandatory consumption of a small meal
containing carbohydrates 2 h prior to exercise and no
further food until test completion).
Statistical analysis
All data were analyzed using R statistical software (v. 3.5.1;
R Core Team) on R Studio (v. 1.1.456; RStudio, Inc) for
Windows 10.
Sample size planning for a future definitive trial
First, the mean gain score for changes in chronic psychosocial stress (PSS-10) was divided by the standard
deviation of the gain scores, yielding the operative effect
size dz . Second, a safeguard effect size was computed
by calculating the lower limit of a one-sided 80% CI on
dz (conf.limits.nct: MBESS package v-4.6.0) [46]. A safeguard effect size is designed to guard against imprecise
Prochilo et al. Pilot and Feasibility Studies
(2021) 7:64
Page 7 of 17
estimation of pilot effect estimates by decreasing the magnitude of an effect based on the width of its confidence
interval [47]. These two effect size estimates (hereby population estimates: δz ) were then used as input to an accuracy in parameter estimation sample size analysis with
99% assurance (ss.aipe.sm: MBESS package). This process
was repeated for hypothetical operative between-group d
statistics (hereby: δs ) ranging from 0.8 to 0.2 (ss.aipe.smd:
MBESS package). The latter analysis estimated the sample
size required to detect hypothetical differences (with precision) between T1–T0 gain scores of different arms of a
confirmatory RCT.
Estimation of participant-centered outcomes
It is important to note that the inferential statistics
reported alongside estimations of trial treatment effects
should be considered exploratory. These findings are not
meant to represent the results of a future definitive trial.
Psychosocial stress factors, mindfulness, emotion regulation,
and V̇O2max
Responses to these variables were analyzed using onesample t tests on T1–T0 gain scores (t.test: base R) (sampling units: n = 17; observations = 34). As a sensitivity
test to any assumption violations, these variables were also
analyzed using robust methods based on T1–T0 contrasts
of the 20% trimmed mean difference using a percentile
bootstrap approach (trimpb: Rallfun package v-35; bootstrap samples = 2000) [48]. Unstandardized effect sizes
were reported as the T1–T0 gain score with 95% CIs.
Standardized effect sizes were reported as Cohen’s d using
the standard deviation of the pre-test scores as standardizer (hereby dpretest ), as recommended in Glass et al. [49]
for pre-post designs. This corresponded to the equation:
dpretest =
MT1 − MT0
SDT0
(1)
In the above equation, MT1 refers to the mean of
the post-test, MT refers to the mean of the pre-test,
and SDT0 refers to the standard deviation of the pretest. The 95% CIs on dpretest were computed using the
bias-corrected-and-accelerated (BCa) bootstrap method
with 2000 resamples (boot: boot package v-1.3-22) [50].
Interpretation of dpretest is consistent with Cohen’s d for
between-group designs.
Aerobic economy
These variables included absolute oxygen cost, relative
oxygen cost, heart rate, and perceived exertion (RPE)
(sampling units: n = 13; observations = 104). These data
were arrayed as separate 2 (time: T1 vs. T0) by 4 (velocity: 6, 8, 10, and 12 km/h) within-within factorials and
analyzed using linear mixed models fit by REML (lmer:
lmerTest package v-3.1-0) [51]. Fixed effect intercepts
were included for time, velocity, and their interaction, and
random effect intercepts were included for participants.
The final model equation was:
y ∼ time × velocity + (1 | participant)
(2)
To determine whether random participant intercepts
improved model fit, REML-likelihood ratio tests of
the model with and without random intercepts were
performed (ranova: lmerTest package). Satterthwaite’s
degrees of freedom was used to evaluate the significance
of F tests for fixed effects terms (anova: lmerTest package)
and t tests for follow-up pairwise comparisons (emmeans:
emmeans package v-1.3.2) [52], as recommended by [53].
Fixed effects yielding p < .05 were followed up with
pairwise contrasts of T1–T0 gain scores. Unstandardized
effect sizes were reported as T1–T0 gain scores with 95%
CIs. Because of the method by which variance is partitioned in mixed models [54], standardized effect sizes
were not computed as there is no widely agreed-upon
method of doing so.
Results
Figure 1 shows the Consolidated Standards of Reporting
Trials (CONSORT) diagram for participant flow through
the study. Twenty-four participants were allocated to the
intervention and 70.8% provided full data. The final sample size was N = 17 (baseline data is given in Table 1). This
satisfied our sample requirements, and no attempts were
made toward further data collection. All participants who
completed this study met the adherence requirements,
and the overall dosage results are reported in Table 2.
Protocol feasibility
Retention rate
Of the 24 participants allocated into the study, n = 17
completed the intervention (retention rate = 70.83%).
Assessment response rate
All participants provided paired data points for chronic
psychosocial stress, mindfulness, use of emotion regulation strategies, and V̇ O2max (response rate = 100%).
For assessments of aerobic economy, n = 17 participants
reached a steady-state velocity at 6 and 8 km/h (100%), n
= 14 reached 10 km/h (82.4%), n = 13 reached 12 km/h
(76.5%), and n = 4 reached 14 km/h (23.5%).
Recruitment rate and sample size planning for a future
definitive trial
Of the 45 participants who expressed interest in participation, n = 24 met the inclusion criteria and agreed to
participate (recruitment rate = 53.3%). The results of the
sample size planning analysis are presented in Table 3.
It is feasible to detect within-group changes (with precision) up to δz = −0.37 and between-group differences
Prochilo et al. Pilot and Feasibility Studies
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Page 8 of 17
Fig. 1 CONSORT flow chart
in gain scores (with precision) up to δs = 0.50. Betweengroup differences in gain scores of δs = 0.40 are detectable
with 80% power, but without precision. Detection of small
between-group effects below these values is infeasible.
Estimation of participant-centered outcomes
Psychosocial stress factors, mindfulness, emotion regulation,
and V̇O2max
Summarized results of these analyses are given in Table 4.
Chronic psychosocial stress There was an overall
reduction in our primary dependent measure of chronic
psychosocial stress (PSS-10; M = −4.24, 95% CI
[−7.84, −0.63], p = .024; see Fig. 2). This effect was also
robust (pR = .020). Twelve participants reported a reduction on the PSS-10, and five participants reported no
change or an increase. In common language, there was a
72.7% chance that a participant picked at random would
Table 1 Baseline demographic characteristics of participants
All participants
PSS declined
PSS increased or no change
Total n (%)
17 (100.00%)
12 (70.59%)
5 (29.41%)
Mean baseline PSS-10 (SD)
20.12 (7.56)
23.50 (5.35)
12.00 (5.74)
Mean age in years (SD)
22.88 (2.71)
23.08 (2.84)
22.40 (2.61)
Gender: male n (%)
8 (47.06%)
5 (29.41%)
3 (17.65%)
Gender: female n (%)
9 (52.94%)
7 (41.18%)
2 (11.76%)
Ethnicity: Caucasian n (%)
11 (64.71%)
7 (41.18%)
4 (23.53%)
Ethnicity: Asian n (%)
6 (35.29%)
5 (29.41%)
1 (5.88%)
Mean baseline V̇O2max
45.34 (7.44)
45.81 (5.58)
44.20 (11.54)
Mean baseline BMI (SD)
23.29 (2.65)
23.96 (2.45)
21.68 (2.64)
SD = standard deviation; n = count; PSS-10 = Perceived Stress Scale; V̇O2max = maximal aerobic capacity; BMI = body mass index
Prochilo et al. Pilot and Feasibility Studies
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Table 2 Summarized dosage results
M (SD)
Range
MBI attendance (%)
79.41 (11.64)
62.50–100.00
Formal meditation (h)
24.81 (2.69)
19.33–29.42
Total running sessions
34.76 (5.39)
25.00–42.00
Mean exercise intensity (% V̇O2max )
70.54 (6.69)
56.78–82.15
Running distance (km)
228.10 (81.67)
143.80–474.27
Running time (h)
24.50 (6.82)
17.99–45.37
M = mean; SD = standard deviation; h = hours; km = kilometers; V̇O2max = maximal
aerobic capacity; MBI = mindfulness-based intervention
report a lower PSS-10 score following the study compared
to before the study. Because seven participants dropped
out of the study, we also assessed whether survivorship
bias was a threat to the validity of this test result. To
this end, we conducted a last observation carried forward
analysis which included the last known state of the subject
in the analysis under the assumption they would report
no change had they completed the study. This analysis
yielded a small decline in effect size magnitude, but the
test remained statistically significant (M = −3.00 95% CI
[−5.61, −0.39], p = .026, pR = .018).
Reductions in PSS-10 were corroborated by improvement in several secondary stress measures. There was an
overall reduction in stress symptoms (M = −4.59, 95% CI
[−6.73, −2.44], p < .001) and depressive symptoms (M =
−4.00, 95% CI [−7.25, −0.75], p = .019), and an overall
improvement in global wellbeing (M = 9.65, 95% CI [1.55,
17.75], p = .023). These effects were also robust. However,
we are insufficiently confident to comment on the direction of change in anxiety (M = 0.12, 95% CI [−2.22, 2.46],
p = .916). A robust test did not change this conclusion.
Page 9 of 17
Mindfulness Participants reported an overall increase in
dispositional mindfulness (M = 0.22, 95% CI [−0.17, 0.60],
p = .256). However, these data are compatible with a 0.17
unit decrease in mindfulness as well as a 0.60 unit increase
in mindfulness. Therefore, we are insufficiently confident
to comment on the direction of this change. A robust test
did not change this conclusion.
Emotion regulation There was a mean improvement
in the use of cognitive reappraisal (M = 0.86, 95% CI
[0.33, 1.39], p = .003). This effect was robust. There was
a mean reduction in the use of maladaptive rumination
(M = −1.41, 95% CI [−2.72, −0.10], p = .037). However,
this effect was not robust (pR = .051). Finally, there was an
overall reduction in the disposition to worry (M = −6.18,
95% CI [−11.34, −1.01], p = .022). This effect was also
robust.
V̇ O2max There was a negligible change in V̇ O2max
(M = 0.25, 95% CI [−2.83, 3.32], p = .868). However, we are
insufficiently confident to comment on the overall direction of this change. A robust test did not change this
conclusion.
Aerobic economy
Summarized results of aerobic economy analyses are
given in Table 5. Modeling variability in participant intercepts improved model fit for each mixed model (ps < .001;
see Supplementary Results Tables 1 through 4). The
assumptions of linearity, homoskedasticity, and normality of residuals were adequate for each mixed model, and
Table 3 Range of sample sizes required to estimate PSS-10 effects for a confirmatory RCT comparing aerobic exercise, mindfulness,
combination training, and a control arm
Population effect
Target MoE
N required per cell
N adjusted
N required per cell per trial
Feasible
−0.60
0.30
63
89
9
Yes
−0.37
0.18
132
186
19
Yes
0.80
0.40
59
84
9
Yes
0.70
0.35
73
103
11
Yes
0.60
0.30
96
136
14
Yes
0.50
0.25
133
188
19
Yes
0.40
0.20
202
285
29
*Yes
0.30
0.15
352
496
50
No
0.20
0.10
779
1098
110
No
δz
δs
δz = within-group (T1–T0) gain in PSS-10; δs = between-group differences in gain scores between different arms of a future RCT; MoE = margin-of-error (i.e., the 95%
confidence interval half-width); N = number of participant; per cell = paired observations (δz ) or observations per arm of a future RCT (δs ), N adjusted = N required per cell
adjusted for the retention rate observed in the pilot study. Feasibility is judged against 10 repetitions of the trial over a 5-year period with a maximum of N = 20 per treatment
arm across each repetition (i.e., total N = 80 per trial). Yes = trial is feasible. *Yes = trial is not feasible using accuracy in parameter estimation criteria; however, the effect is
detectable with 80% power. No = trial is infeasible
Prochilo et al. Pilot and Feasibility Studies
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Table 4 Summarized results for pre-test (T0), post-test (T1), and gains (T1–T0) for psychosocial stress factors, mindfulness, emotion
regulation factors, and maximal aerobic capacity
T0: M (SD)
T1: M (SD)
Gain: M (SD) [95% CI]
dpretest [95% CI]
t
p
pR
15.88 (4.54)
−4.24 (7.01) [−7.84, −0.63]
−0.56 [−1.14, −0.06]
−2.49
.024
.020
Psychosocial stress
PSS-10
20.12 (7.56)
DASS-21 (S)
28.59 (6.07)
24.00 (5.87)
−4.59 (4.17) [−6.73, −2.44]
−0.76 [−1.24, −0.52]
−4.54
< .001
< .001
DASS-21 (A)
19.88 (4.82)
20.00 (6.60)
0.12 (4.55) [−2.22, 2.46]
0.02 [−0.43, 0.53]
0.11
.916
.789
DASS-21 (D)
23.76 (7.21)
19.76 (4.63)
−4.00 (6.32) [−7.25, −0.75]
−0.56 [−0.98, −0.15]
−2.61
.019
.015
WHO-5
54.35 (18.55)
64.00 (12.65)
9.65 (15.75) [1.55, 17.75]
0.52 [0.19, 1.02]
2.53
.023
.028
3.78 (0.70)
4.00 (0.66)
0.22 (0.75) [−0.17, 0.60]
0.31 [−0.24, 0.88]
1.18
.256
.225
Mindfulness
MAAS
Emotion regulation
ERQ-CR
4.31 (1.46)
5.18 (1.18)
0.86 (1.04) [0.33, 1.39]
0.59 [0.22, 1.15]
3.43
.003
.003
RRS-BR
11.00 (4.14)
9.59 (3.36)
−1.41 (2.55) [−2.72, −0.10]
−0.34 [−0.75, −0.07]
−2.28
.037
.051
PSWQ
50.12 (16.19)
43.94 (11.26)
−6.18 (10.05) [−11.34, −1.01]
−0.38 [−0.78, −0.05]
−2.53
.022
.012
45.34 (7.44)
45.58 (8.91)
0.25 (5.98) [−2.83, 3.32]
0.03 [−0.51, 0.42]
0.17
.868
.642
Aerobic capacity
V̇O2max
Sampling units: N = 17 and observations = 34. Degrees of freedom for Student’s t test = 16. M mean, SD = standard deviation; CI = confidence interval; dpretest = Cohen’s d with
pre-test standard deviation as standardizer; p = p value; pR = robust p value; PSS = Perceived Stress Scale; DASS-21 = Depression Anxiety Stress Scales (S = stress; A = anxiety;
D = depression), WHO-5 = World Health Organization Wellbeing Index; MAAS = Mindful Attention Awareness Scale; ERQ-CR = cognitive reappraisal subscale of the Emotion
Regulation Questionnaire; RRS-BR = brooding subscale of the Ruminative Responses Scale; PSWQ = Penn State Worry Questionnaire; V̇O2max = maximal aerobic capacity
Fig. 2 a Means and 95% confidence intervals (CIs) at pre-test (T0) and post-test (T1) for responses to the PSS-10. Unfilled circles represent individual
participant data points, and dashed lines join paired responses for each participant. b T1–T0 gain scores for the PSS-10, where (from largest to
smallest) the error bar represents 95%, 90%, 85%, and 80% CIs. Unfilled circles represent individual gain scores, and a dashed line marks the null
hypothesis of zero gain. PSS-10 = Perceived Stress Scale
(2021) 7:64
Prochilo et al. Pilot and Feasibility Studies
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Table 5 Summarized Type III ANOVA table of the linear mixed model (fit by REML) for each aerobic economy outcome
SS
MS
df
F
p
Oxygen Cost
Main Effect of Time
0.49
0.49
1,84
7.57
.007
Main Effect of Velocity
40.23
13.41
3,84
209.18
<.001
Time × Velocity Interaction
0.23
0.08
3,84
1.20
.316
Relative Oxygen Cost
Main Effect of Time
495.99
495.99
1,84
16.09
<.001
Main Effect of Velocity
35315.81
11771.94
3,84
381.90
<.001
Time × Velocity Interaction
175.98
58.66
3,84
1.90
.135
Main Effect of Time
541.73
541.73
1,84
8.13
.005
Main Effect of Velocity
47653.51
15884.50
3,84
238.43
<.001
Time × Velocity Interaction
51.82
17.27
3,84
0.26
.855
Main Effect of Time
13.16
13.16
1,84
13.93
<.001
Main Effect of Velocity
673.57
224.52
3,84
237.52
<.001
Time × Velocity Interaction
1.49
0.50
3,84
0.53
.666
Heart rate
Perceived Exertion (RPE)
Note. Sampling Units: N = 13 and observations = 104; SS = sum of squares; MS = mean square; F = F statistic; df = degrees of freedom; p = p value. F tests use Satterthwaite’s
degrees of freedom
a sensitivity test revealed no evidence of participant and
response-level outliers in each model.
in heart rate across all velocities (M = −4.56, 95% CI
[−7.75, −1.38]; see Fig. 3c).
Absolute oxygen cost There was a statistically significant main effect of time (F(1, 84) = 7.57, p = .007) and
velocity (F(3, 84) = 209.18, p < .001). We are insufficiently
confident to comment on the presence of an interaction
(F(3, 84) = 1.20, p = .316). A pairwise (T1–T0) contrast
of the main effect of time indicated that, on average, there
was a change in oxygen cost across all velocities of −0.14
V̇ O2 L/min (95% CI [−0.24, −0.04]; see Fig. 3a).
Perceived exertion (RPE) There was a statistically significant main effect of time (F(1, 84) = 13.93, p < .001) and
velocity (F(3, 84) = 237.52, p < .001). We are insufficiently
confident to comment on the presence of an interaction
(F(3, 84) = 0.53, p = .666). A pairwise (T1–T0) contrast
of the main effect of time indicated there was, on average,
a decrease in RPE across all velocities following the study
(M = −0.71, 95% CI [−1.09, −0.33]; see Fig. 3d).
Relative oxygen cost There was a statistically significant
main effect of time (F(1, 84) = 16.09, p < .001) and velocity
(F(3, 84) = 381.90, p < .001). We are insufficiently confident to comment on the presence of an interaction at a .05
threshold (F(3, 84) = 1.90, p = .135). A pairwise (T1–T0)
contrast of the main effect of time indicated that, on average, there was a decrease in %V̇ O2max across all velocities
following the study (M=−4.37, 95% CI [−6.53, −2.20]; see
Fig. 3b).
Discussion
Heart rate There was a statistically significant main
effect of time (F(1, 84) = 8.13, p = .005) and velocity (F(3,
84) = 238.43, p < .001). We are insufficiently confident to
comment on the presence of an interaction (F(3, 84) =
0.26, p = .855). A pairwise (T1–T0) contrast of the main
effect of time indicated there was, on average, a decrease
Protocol feasibility
This study was a single-arm pre-post pilot and feasibility
study of an intervention comprised of aerobic exercise and
mindfulness-based training delivered concurrently over
16 weeks. The first aim of this study was to obtain sufficient assurance of protocol feasibility to determine if
a definitive RCT comparing aerobic exercise, mindfulness, combination training, and a control arm was an
appropriate trial design. We considered retention rate,
assessment response rate, recruitment rate, and required
sample size for a confirmatory trial as measures of feasibility. The retention rate was 70.8%, which was above the
required rate of 65.0%. This is also above the lower limit
of retention identified for mindfulness-based intervention
(MBI) training in healthy individuals [6] and for previously
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Fig. 3 Dot plots of aerobic economy data across velocity and time for a absolute oxygen cost (V̇O2max L/min), b relative oxygen cost (%V̇O2max ), c
heart rate (beats/min), and d perceived exertion (RPE). The estimated marginal means for each velocity at pre-test (T0) are marked by filled black
circles, and at post-test (T1) are marked by filled black triangles. Each unfilled circle represents an individual participant data point. Error bars
represent 95% CIs
non-exercising individuals [35]. This indicates that the
current intervention may be feasible when compared to
already existing interventions that yield salutary mental
health outcomes. Furthermore, the assessment response
rate for pre-post measures with single paired data points
was 100%. This included our primary dependent outcome
measure of chronic psychosocial stress (PSS-10). This
indicates that the trial is feasible from a data collection
perspective. However, participants varied in the steadystate velocity attained during assessments of aerobic economy. This was unavoidable given that participants differed
in cardiorespiratory fitness at baseline. For this reason, it
may be necessary to continue to regard aerobic economy
as a secondary measure based on a subgroup analysis in a
future confirmatory trial. Finally, given that the combination treatment arm comprises all elements of a future RCT
and is the most labor intensive for participants, these rates
may also be reasonable estimates for each arm of a future
RCT.
The study recruitment rate was 53.3%. Across a 2month recruitment period (i.e., 1 month of recruitment
at each wave of a future definitive trial) and with a
total of 45 applicants, this is indicative of a recruitment
potential of 12 participants per month for the combination trial arm of a future RCT. With an expanded
research team for recruitment, assessment, and facilitation of the intervention, a recruitment potential of 12
participants per month per treatment arm of an RCT
(i.e., four arms: n = 48) may represent a reasonable estimate of recruitment feasibility. Based on our sample size
analysis, precise estimation of within-group changes in
PSS-10 gain scores requires between 89 (δz = −0.60)
and 186 (δz = −0.37) paired observations. A precise estimate of differences in gain scores between each arm
of an RCT will require between 84 (large difference: δs
= 0.80) and 1098 (small difference: δs = 0.20) observations per cell. These calculations reflect a retention rate
of 70.8%.
Prochilo et al. Pilot and Feasibility Studies
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Under the assumption that an RCT is only feasible with
n = 20 per treatment arm (i.e., total N = 80 per trial)
across 10 trial repetitions over 5 years, the total maximum
number of participants is n = 200 per treatment arm (i.e.,
total N = 800). A recruitment rate of n = 12 per treatment arm per month is therefore feasible to fill each trial
run following the second month of the protocol (estimated
sample at month 2: n = 24 per treatment arm) with a start
date at month 3 following assessments. Assuming recruitment continues ongoing each month, each trial start date
will satisfactorily attain n = 20 participants per treatment
arm. Assuming a retention rate of 70.8%, a total recruitment of n = 200 per treatment arm by the end of the
protocol is satisfactory to detect within-group changes in
PSS-10 gain scores (with precision) as low as δz = −0.37,
and between-group difference in gain scores (with precision) up to δs = 0.50. Differences in gain scores of δs =
0.40 will be detectable with 80% power, but these effects
may have lower than desired precision. Estimation of very
small differences in gain scores (i.e., δs ≤ 0.30) is infeasible.
Based on these criteria, we conclude that there is sufficient
assurance of protocol feasibility to conduct a confirmatory
RCT under the above assumptions and detect most effects
precisely (or as a minimal requirement, statistically).
Of course, however, these above assumptions do not
take into consideration additional uncertainties that may
impact the capacity of a single research group to conduct
a confirmatory trial. This includes uncertainty in future
economic conditions, finances, and resource availability.
Therefore, this confirmatory trial may be more appropriately suited to a large multisite clinical trial that spreads
risk of conducting 10 trial repetitions across multiple
research groups. This approach has the additional benefit of evaluating the trial treatment effect across large and
heterogeneous populations in varied treatment settings,
and will therefore mitigate multiple threats to the validity
of observed effects.
Additional considerations for a future definitive trial
may also include ensuring that the effects of the
intervention are not driven by differences in baseline
stress levels or baseline cardiorespiratory fitness levels
that differ across groups. While randomization ensures
that these differences, on average, should be equal across
treatment arms, one option would be to perform block
stratified random assignment on factors that might bias
results for each trial repetition. With regard to baseline
stress, this could include block randomization based on a
simple one-item question about overall stress levels that
is embedded in the initial application to the intervention,
as recommended by Shadish and colleagues [55]. This is
particularly important for extending the program to the
general public, which, unlike our student sample, does
not necessarily have specific low-stress periods within
the calendar year to serve as baseline. With respect to
Page 13 of 17
cardiorespiratory fitness, baseline levels of V̇ O2max might
also be important to consider within the block stratified
random assignment procedure, particularly if the effects
of the intervention are driven, in part, by changes in
cardiorespiratory fitness.
A further consideration for a future definitive trial may
be to broaden the trial eligibility criteria to allow findings
to be more generalizable. Currently, the eligibility criteria
only allowed for young and relatively healthy adults as part
of a prevention-focused intervention. While this population was the target of interest, it may not be the population
that needs this intervention most. However, any deviation
from the methods and protocol of this study may require
further pilot testing prior to performing a definitive trial.
Estimation of participant-centered outcomes
The second aim of this study was to estimate the range
and direction of within-group changes in chronic psychosocial stress (PSS-10) in a nonclinical sample. Our
analysis indicated that, overall, chronic psychosocial stress
(as measured by the PSS-10 scale) declined following
the study. Reductions on the PSS-10 scale of the magnitude observed in this study have been considered clinically meaningful in past research utilizing this measure [56–58]. The meta-analytic estimate of the effect
of (controlled) mindfulness-based interventions on stress
outcomes in healthy participants has been reported as
d = −0.74 [−1.07, −0.41] [6]. If this effect estimate
and confidence interval represents the average effect of
mindfulness-based training on stress-related measures,
our current observed effect size of −0.56 could be considered average or moderate in magnitude. This standardized
change is also within the range reported meta-analytically
for mental health improvements observed following aerobic exercise interventions [5, 20]. Based on these observations, there is insufficient evidence to suggest that combination training yields improvements in chronic psychosocial stress over and above each intervention alone. However, the confidence interval (CI) on our effect indicates
that the estimate of change in PSS-10 in this study is very
imprecise. The 95% CIs on this effect are consistent with
reductions in PSS-10 that could be considered smaller
than average, or even above average.
Further support for the validity of a reduction in PSS10 scores comes from changes in our secondary mental
health outcome measures. This included a reduction in
stress and depressive symptoms, and an improvement in
global wellbeing. Indeed, mean improvement in wellbeing was of a magnitude of approximately 10 percentage
points on the WHO-5 scale, which is indicative of a
clinically relevant improvement with respect to the scale
[59]. However, we are insufficiently confident to comment on the direction and magnitude of change in anxiety
symptoms.
Prochilo et al. Pilot and Feasibility Studies
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Participants reported an overall increase in dispositional mindfulness. This represented a partial unit change
from somewhat frequently to somewhat infrequently, in
response how frequent participants reported an absence
of attention to or awareness of present moment experiences. However, the confidence intervals on these data
are also compatible with a partial unit decrease in mindfulness, as well as a greater than half unit increase in
mindfulness. Therefore, we are insufficiently confident to
comment on the direction of change of this effect in the
present study.
Dispositional mindfulness represents the quality of
attention and awareness with which one attends to the
present moment experience, and is considered a core
mechanistic component of how MBIs exert their effects
[10, 60]. In the present study, participants reported an
average of 24.81 h of formal meditation practice, which
is within the range of practice reported meta-analytically
in a typical MBI in healthy participants [6]. The metaanalytic estimate of the effect of MBIs on mindfulness in
the above publication was d = 0.60, 95% CI [0.36, 0.85].
The small magnitude of change in mindfulness in the
present study is therefore unexpected (i.e., dpretest = 0.31,
95% CI [−0.24, 0.88]). However, it must be noted that
measures of mindfulness are not consistently reported
for MBI interventions [6], and over half of the studies
reported in a recent meta-analysis found no significant
effect following MBI training [61].
Participants reported an overall increase in use cognitive reappraisal. In descriptive terms, this represented a
unit change from neither agree or disagree to agree, in
response to questions evaluating the disposition to use
this emotion regulation strategy. Evidence from intervention studies [62, 63] demonstrates that mindfulness and
MBI training are often implicated with a greater capacity for this emotion regulation strategy. Improvement in
cognitive reappraisal is also considered central to some
mindfulness theories [62], although it is considered nonessential or secondary to others [18]. Beyond reappraisal,
participants reported a decrease in the use of maladaptive
rumination and worry. Compared to the meta-analytic
estimate of the effect of mindfulness-based training on
stress [6], these effects might be considered small in magnitude. A reduction in these aspects of repetitive negative
thinking has been implicated in meta-analyses as mechanisms of mindfulness [15]. However, the effect of this
study on rumination was not robust. That is, when sampling from a population where a null hypothesis of no
change in rumination in the majority of individuals is true,
the magnitude of change in this parameter in the present
study is expected to occur at a rate of pR = .051 (i.e.,
5.10% of the time). Notably, there were no outliers in this
variable and no evidence of a strong deviation from normality, meaning that the standard (i.e., non-robust) test
Page 14 of 17
may be a more appropriate reflection of the data. This
interpretation is strengthened by observation that Alderman and colleagues [7] reported a statistical reduction in
rumination following combination training in their study.
Although, we must caution over-interpretation of these
small sample pilot results given their large CIs.
Finally, with respect to cardiorespiratory fitness, there
was a negligible overall change in V̇ O2max following the
intervention. On average, participants reported a V̇ O2max
value between 45 and 46 at both time points. Metaanalytic evidence suggests that aerobic interventions similar to the so-called Hickson protocol [64] are most reliably
implicated in improvement in this parameter [65]. This
involves 10 weeks of aerobic exercise involving a combination of endurance training (i.e., consistent exercise for
a specified time period without break) and interval training (i.e., bursts of high-intensity output ≥ 91% V̇ O2max ).
While the current intervention involved a combination of
continuous and interval training, it is plausible the mean
intensity at which participants conducted exercise (i.e.,
70% of their V̇ O2max ) and frequency (i.e., 2.32 runs per
week) was insufficient to yield improvement in overall
V̇ O2max . Given that the present trial intervention may be
unlikely to improve V̇ O2max , one option for a future trial
would be to include additional measures of cardiorespiratory fitness. This might include assessment of specific
fitness objectives (e.g., a 500 meter run) as secondary
fitness outcomes.
However, there were improvements in aerobic economy across steady-state (submaximal) exercise velocities
in our subgroup analyses. This included a reduction in
absolute oxygen cost, relative oxygen cost, heart rate,
and perceived exertion. Improvement in indices of aerobic economy is indicative of a cascade of metabolic and
cardiopulmonary effects that result in better use of oxygen (i.e., increased energy production) relative to a given
exercise intensity. This includes more efficient cardiorespiratory responses (e.g., lower heart rate), thermoregulation (e.g., changes in core body temperature), and substrate metabolism [26]. The relationship between these
parameters and mental health is relatively understudied.
However, several theories assert that exercise adaptations
such as these may be associated with resilience to acute
psychosocial stress, with potential implications for overall mental health [23]. It is therefore plausible that the
salutary effects following training in this intervention are
partially determined by improvements in aerobic economy. However, note well that these effects are imprecise.
This is reflected in the large CIs on each of the reported
effects.
Strengths, limitations, and generalizability
Notable strengths of this study included the following:
(1) use of a full mindfulness psychoeducation program in
Prochilo et al. Pilot and Feasibility Studies
(2021) 7:64
contrast to a single mindfulness component (e.g., focusedattention meditation alone); (2) use of an aerobic exercise
program that prescribed exercise of a duration, frequency,
and intensity that has been clinically shown to improve
or maintain aerobic fitness; (3) complete individualization of aerobic exercise prescriptions through objective
cardiorespiratory fitness assessments; (4) comprehensive
monitoring of training compliance through GPS data; (5)
provision of a detailed methodological protocol that is
presented here in sufficient detail to allow for replication; and (6) extensive quantification of multiple protocol
feasibility criteria.
However, the clearest limitation is that a single-arm
study design presents with difficulty in distinguishing
between the effects of the treatment and several threats to
validity. For example, the observed reduction in chronic
psychosocial stress may be an effect of intervention exposure, but it may also be partly explained through a placebo
effect, maturation, test effects, or regression to the mean.
However, regression to the mean may be a less plausible explanation as this study was designed to coincide
with low-stress periods with respect to our study population. Further limitations include that effects have been
estimated with low precision (although this is a limitation that characterizes almost all pilot studies). For these
reasons, we must emphasize that all results should be
treated as preliminary and for readers to avoid exaggerated generalizations of findings. Within the present study,
the single-arm research design was an efficient use of limited resources to examine most uncertainties that may
arise in each arm of a definitive trial, and to determine
feasibility estimates for such a trial. Finally, it is important
to note that the results of this study are mostly generalizable to nonclinical populations of young, healthy, and
university educated adults.
Conclusion
Retention rate and assessment response rate were acceptable, and a sample size analysis indicated that it is feasible
to detect most effects in a definitive trial with precision.
We recommend that a definitive randomized controlled
trial is feasible and should proceed.
Supplementary Information
The online version contains supplementary material available at
https://doi.org/10.1186/s40814-020-00751-6.
Additional file 1: Supplementary Materials.
Additional file 2: Supplementary Results.
Acknowledgements
The Melbourne Statistical Consulting Platform provided guidance and
feedback on the analysis of linear mixed models.
Page 15 of 17
Authors’ contributions
G.A.P. designed the trial and statistical analysis strategy, recruited all
participants, conducted the mindfulness and aerobic exercise coaching,
collected all data, scripted the analysis code in R, performed all analyses, wrote
the manuscript, and compiled the manuscript. R.J.S.C. conducted the
incremental exercise protocol. R.J.S.C. and P.M. provided guidance on
experimental design and data interpretation. R.J.S.C., P.M., C.H., and R.C.
provided feedback on manuscript development. The authors read and
approved the final manuscript.
Funding
This work was partly supported by the Melbourne Research Scholarship
awarded to G.A.P. by the University of Melbourne, and a Heart Foundation
Future Leader Fellowship (1000458) awarded to P.M.
Availability of data and materials
The Supplementary Materials, Supplementary Results, CONSORT checklist, R
statistical software analysis scripts, and instructions for reproducing all findings
are available at the following GitHub repository: https://github.com/gprochilo/
stress_trial. The deidentified data are available from the corresponding author
upon a reasonable request. These data are not publicly available on the advice
of the Monash Ethics Committee because the approved ethics application did
not include provisions for public access to data.
Ethics approval and consent to participate
All participants provided informed written consent which was approved by
the Monash University Human Research Ethics Committee (project number:
CF15/3863 - 2015001705).
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1 Melbourne School of Psychological Sciences, University of Melbourne,
Melbourne, Australia. 2 ISN Psychology, Institute for Social Neuroscience,
Melbourne, Australia. 3 Department of Nutrition Dietetics & Food, Monash
University, Melbourne, Australia. 4 Department of General Practice, Monash
University, Melbourne, Australia. 5 Mindfulness Programs, Monash University,
Melbourne, Australia.
Received: 30 November 2019 Accepted: 16 December 2020
References
1. Pizzagalli DA. Depression, stress, and anhedonia: toward a synthesis and
integrated model. Annu Rev Clin Psychol. 2014;10:393–423. https://doi.
org/10.1146/annurev-clinpsy-050212-185606.
2. Theorell T, Hammarström A, Aronsson G, Träskman Bendz L, Grape T,
Hogstedt C, Marteinsdottir I, Skoog I, Hall C. A systematic review
including meta-analysis of work environment and depressive symptoms.
BMC Public Health. 2015;15(1):738. https://doi.org/10.1186/s12889-0151954-4.
3. McEwen B, Gianaros PJ. Stress- and allostasis-induced brain plasticity.
Annu Rev Med. 2011;62(1):431–45. https://doi.org/10.1146/annurevmed-052209-100430.
4. Wirtz PH, von Känel R. Psychological stress, inflammation, and coronary
heart disease. Curr Cardiol Rep. 2017;19(11):111. https://doi.org/10.1007/
s11886-017-0919-x.
5. Cooney GM, Dwan K, Greig CA, Lawlor DA, Rimer J, Waugh FR,
McMurdo M, Mead GE. Exercise for depression. Cochrane Database Syst
Rev. 2013;9:CD004366. https://doi.org/10.1002/14651858.CD004366.
pub6.
6. Khoury B, Sharma M, Rush SE, Fournier C. Mindfulness-based stress
reduction for healthy individuals: a meta-analysis. J Psychosom Res.
2015;78(6):519–28. https://doi.org/10.1016/j.jpsychores.2015.03.009.
7. Alderman BL, Olson RL, Brush CJ, Shors TJ. Map training: combining
meditation and aerobic exercise reduces depression and rumination
while enhancing synchronized brain activity. Transl Psychiatry. 2016;6:
726. https://doi.org/10.1038/tp.2015.225.
Prochilo et al. Pilot and Feasibility Studies
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
(2021) 7:64
Shors TJ, Olson RL, Bates ME, Selby EA, Alderman BL. Mental and
physical (map) training: a neurogenesis-inspired intervention that
enhances health in humans. Neurobiol Learn Mem. 2014;115:3–9. https://
doi.org/10.1016/j.nlm.2014.08.012.
Creswell JD. Mindfulness interventions. Annu Rev Psychol. 2017;68:
491–516. https://doi.org/10.1146/annurev-psych-042716-051139.
Lindsay EK, Creswell JD. Mechanisms of mindfulness training: monitor
and acceptance theory (mat). Clin Psychol Rev. 2017;51:48–59. https://
doi.org/10.1016/j.cpr.2016.10.011.
Kabat-Zinn J. Full catastrophe living: using the wisdom of your body and
mind to face stress, pain, and illness fifteenth anniversary edition. New
York, NY: Bantam Dell; 2005.
Teasdale JD, Segal ZV, Williams JMG, Ridgeway VA, Soulsby JM, Lau MA.
Prevention of relapse/recurrence in major depression by
mindfulness-based cognitive therapy. J Consult Clin Psychol. 2000;68(4):
615.
Crane RS, Brewer J, Feldman C, Kabat-Zinn J, Santorelli S, Williams JMG,
Kuyken W. What defines mindfulness-based programs? The warp and the
weft. Psychol Med. 2016;47(6):990–9. https://doi.org/10.1017/
S0033291716003317.
Parsons CE, Crane C, Parsons LJ, Fjorback LO, Kuyken W. Home practice
in mindfulness-based cognitive therapy and mindfulness-based stress
reduction: a systematic review and meta-analysis of participants’
mindfulness practice and its association with outcomes. Behav Res Ther.
2017;95:29–41. https://doi.org/10.1016/j.brat.2017.05.004.
Gu J, Strauss C, Bond R, Cavanagh K. How do mindfulness-based
cognitive therapy and mindfulness-based stress reduction improve
mental health and wellbeing? A systematic review and meta-analysis of
mediation studies. Clin Psychol Rev. 2015;37:1–12. https://doi.org/10.
1016/j.cpr.2015.01.006.
Hoogendoorn WE, van Poppel MN, Bongers PM, Koes BW, Bouter LM.
Systematic review of psychosocial factors at work and private life as risk
factors for back pain. Spine (Phila Pa 1976). 2000;25(16):2114–25. https://
doi.org/10.1097/00007632-200008150-00017.
Garland EL, Farb NA, Goldin PR, Fredrickson BL. The
mindfulness-to-meaning theory: Extensions, applications, and challenges
at the attention-appraisal-emotion interface. Psychol Inq. 2015;26(4):
377–87. https://doi.org/10.1080/1047840X.2015.1092493.
Chambers R, Gullone E, Allen NB. Mindful emotion regulation: an
integrative review. Clin Psychol Rev. 2009;29(6):560–72. https://doi.org/
10.1016/j.cpr.2009.06.005.
WHO. Global recommendations on physical activity for health. Technical
report. 2010.
Stubbs B, Vancampfort D, Rosenbaum S, Firth J, Cosco T, Veronese N,
Salum GA, Schuch FB. An examination of the anxiolytic effects of exercise
for people with anxiety and stress-related disorders: a meta-analysis.
Psychiatry Res. 2017;249:102–8. https://doi.org/10.1016/j.psychres.2016.
12.020.
Wipfli BM, Rethorst CD, Landers DM. The anxiolytic effects of exercise: a
meta-analysis of randomized trials and dose-response analysis. J Sport
Exerc Psychol. 2008;30(4):392–410.
DeFina LF, Haskell WL, Willis BL, Barlow CE, Finley CE, Levine BD,
Cooper KH. Physical activity versus cardiorespiratory fitness: two (partly)
distinct components of cardiovascular health? Prog Cardiovasc Dis.
2015;57(4):324–9. https://doi.org/10.1016/j.pcad.2014.09.008.
Sothmann MS, Buckworth J, Claytor RP, Cox RH, White-Welkley JE,
Dishman RK. Exercise training and the cross-stressor adaptation
hypothesis. Exerc Sport Sci Rev. 1996;24:267–87.
Schnohr P, Kristensen TS, Prescott E, Scharling H. Stress and life
dissatisfaction are inversely associated with jogging and other types of
physical activity in leisure time–the Copenhagen city heart study. Scand J
Med Sci Sports. 2005;15(2):107–12. https://doi.org/10.1111/j.1600-0838.
2004.00394.x.
Strohle A, Hofler M, Pfister H, Muller AG, Hoyer J, Wittchen HU, Lieb R.
Physical activity and prevalence and incidence of mental disorders in
adolescents and young adults. Psychol Med. 2007;37(11):1657–66.
https://doi.org/10.1017/s003329170700089x.
Barnes KR, Kilding AE. Running economy: measurement, norms, and
determining factors. Sports Med Open. 2015;1:8. https://doi.org/10.1186/
s40798-015-0007-y.
Page 16 of 17
27. Strasser B, Burtscher M. Survival of the fittest: Vo2max, a key predictor of
longevity? Front Biosci (Landmark Ed). 2018;23:1505–16.
28. Hamer M, Stamatakis E. Objectively assessed physical activity, fitness and
subjective wellbeing. Ment Health Phys Act. 2010;3(2):67–71. https://doi.
org/10.1016/j.mhpa.2010.09.001.
29. Lindwall M, Ljung T, Hadžibajramović E, Jonsdottir IH. Self-reported
physical activity and aerobic fitness are differently related to mental
health. Ment Health Phys Act. 2012;5(1):28–34. https://doi.org/10.1016/j.
mhpa.2011.12.003.
30. Kettunen O, Vuorimaa T, Vasankari T. A 12-month exercise intervention
decreased stress symptoms and increased mental resources among
working adults - results perceived after a 12-month follow-up. Int J Occup
Med Environ Health. 2015;28(1):157–68. https://doi.org/10.13075/ijomeh.
1896.00263.
31. de Bruin EI, Formsma AR, Frijstein G, Bögels SM. Mindful2work: effects of
combined physical exercise, yoga, and mindfulness meditations for stress
relieve in employees. A proof of concept study. Mindfulness. 2017;8(1):
204–17. https://doi.org/10.1007/s12671-016-0593-x.
32. Pescatello LS, Arena R, Riebe D, Thompson PD. ACSM’s guidelines for
exercise testing and prescription, 9th ed. edn. Philadelphia: Wolters
Kluwer/Lippincott Williams & Wilkins Health; 2014.
33. Cohen S, Williamson G. In: S S, S O, editors. Perceived stress in a
probability sample of the United States. Newbury Park, CA: Sage; 1988,
pp. 31–67.
34. Whitehead AL, Julious SA, Cooper CL, Campbell MJ. Estimating the
sample size for a pilot randomised trial to minimise the overall trial
sample size for the external pilot and main trial for a continuous outcome
variable. Stat Methods Med Res. 2016;25(3):1057–73. https://doi.org/10.
1177/0962280215588241.
35. Linke SE, Gallo LC, Norman GJ. Attrition and adherence rates of sustained
vs. intermittent exercise interventions. Ann Behav Med Publ Soc Behav
Med. 2011;42(2):197–209. https://doi.org/10.1007/s12160-011-9279-8.
36. Lovibond SH, Lovibond PF. Manual for the depression anxiety stress
scales, 2nd edn. Sydney: Psychology Foundation; 1995.
37. WHO. Use of well-being measures in primary health care - the DepCare
project health for all. Target 12. E60246. Geneva: WHO; 1998.
38. Brown KW, Ryan RM. The benefits of being present: mindfulness and its
role in psychological well-being. J Pers Soc Psychol. 2003;84(4):822–48.
39. Gross JJ, John OP. Individual differences in two emotion regulation
processes: implications for affect, relationships, and well-being. J Pers Soc
Psychol. 2003;85(2):348–62.
40. Treynor W, Gonzalez R, Nolen-Hoeksema S. Rumination reconsidered: a
psychometric analysis. Cogn Ther Res. 2003;27(3):247–59. https://doi.org/
10.1023/A:1023910315561.
41. Griffith JW, Raes F. Factor structure of the ruminative responses scale: a
community-sample study. Eur J Psychol Assess. 2015;31:247–53. https://
doi.org/10.1027/1015-5759/a000231.
42. Meyer TJ, Miller ML, Metzger RL, Borkovec TD. Development and
validation of the penn state worry questionnaire. Behav Res Ther.
1990;28(6):487–95. https://doi.org/10.1016/0005-7967(90)90135-6.
43. Winter EM, Jones AM, Davidson RCR, Bromley PD, Mercer TH, (eds).
Sport and Exercise Physiology Testing Guidelines: Volume I - Sport
Testing: The British Association of Sport and Exercise Sciences Guide (1st
ed). Routledge; 2006. https://doi.org/10.4324/9780203966846.
44. Jones AM, Doust JH. A 1% treadmill grade most accurately reflects the
energetic cost of outdoor running. J Sports Sci. 1996;14(4):321–7. https://
doi.org/10.1080/02640419608727717.
45. Borg G. Ratings of perceived exertion and heart rates during short-term
cycle exercise and their use in a new cycling strength test. Int J Sports
Med. 1982;3(3):153–8. https://doi.org/10.1055/s-2008-1026080.
46. Kelley K. MBESS: The MBESS R Package. R package version 4.6.0. 2019.
https://CRAN.R-project.org/package=MBESS. Accessed 1 Dec 2019.
47. Perugini M, Gallucci M, Costantini G. Safeguard power as a protection
against imprecise power estimates. Perspect Psychol Sci. 2014;9(3):
319–32. https://doi.org/10.1177/1745691614528519.
48. Wilcox RR. Rallfun-v35. 2018. https://dornsife.usc.edu/labs/rwilcox/
software/. Accessed 1 Dec 2019.
49. Glass GV, McGaw B, Smith ML. Meta-Analysis in Social Research: Sage
Publications; 1981.
50. Canty A, Ripley BD. Boot: Bootstrap R (S-Plus) Functions. R package
version 1.3-22. 2019. https://cran.r-project.org/package=boot.
Prochilo et al. Pilot and Feasibility Studies
(2021) 7:64
51. Kuznetsova A, Brockhoff PB, Christensen RHB. lmertest package: tests in
linear mixed effects models. J Stat Softw. 2017;82(13):1–26. https://doi.
org/10.18637/jss.v082.i13.
52. Lenth R. emmeans: estimated marginal means, AKA least-squares means
[R package version 1.3.2]. 2019. https://CRAN.R-project.org/package=
emmeans. Accessed 1 Dec 2019.
53. Luke SG. Evaluating significance in linear mixed-effects models in R.
Behav Res Methods. 2017;49(4):1494–502. https://doi.org/10.3758/
s13428-016-0809-y.
54. Rights JD, Sterba SK. Quantifying explained variance in multilevel models:
An integrative framework for defining R-squared measures. Psychol
Methods. 2019;24(3):309–38. https://doi.org/10.1037/met0000184.
55. Shadish WR, Cook TD, Campbell DT. Experimental and
quasi-experimental designs for generalized causal inference. Boston:
Houghton-Mifflin; 2002.
56. Hölzel BK, Carmody J, Evans KC, Hoge EA, Dusek JA, Morgan L, Pitman
RK, Lazar SW. Stress reduction correlates with structural changes in the
amygdala. Soc Cogn Affect Neurosci. 2010;5(1):11–17. https://doi.org/10.
1093/scan/nsp034.
57. Huang S-L, Li R-H, Huang F-Y, Tang F-C. The potential for
mindfulness-based intervention in workplace mental health promotion:
results of a randomized controlled trial. PLOS ONE. 2015;10(9):0138089.
https://doi.org/10.1371/journal.pone.0138089.
58. Klatt MD, Buckworth J, Malarkey WB. Effects of low-dose mindfulnessbased stress reduction (mbsr-ld) on working adults. Health Educ Behav.
2009;36(3):601–14. https://doi.org/10.1177/1090198108317627.
59. Topp CW, Østergaard SD, Søndergaard S, Bech P. The WHO-5 well-being
index: a systematic review of the literature. Psychother Psychosom.
2015;84(3):167–76.
60. Creswell JD, Lindsay EK. How does mindfulness training affect health? A
mindfulness stress buffering account. Curr Dir Psychol Sci. 2014;23(6):
401–7. https://doi.org/10.1177/0963721414547415.
61. Visted E, Vøllestad J, Nielsen MB, Nielsen GH. The impact of group-based
mindfulness training on self-reported mindfulness: a systematic review
and meta-analysis. Mindfulness. 2015;6(3):501–22. https://doi.org/10.
1007/s12671-014-0283-5.
62. Garland EL, Hanley A, Farb NA, Froeliger BE. State mindfulness during
meditation predicts enhanced cognitive reappraisal. Mindfulness (N Y).
2015;6(2):234–42. https://doi.org/10.1007/s12671-013-0250-6.
63. Garland EL, Hanley AW, Goldin PR, Gross JJ. Testing the
mindfulness-to-meaning theory: Evidence for mindful positive emotion
regulation from a reanalysis of longitudinal data. PLOS ONE. 2017;12(12):
0187727. https://doi.org/10.1371/journal.pone.0187727.
64. Hickson RC, Bomze HA, Holloszy JO. Linear increase in aerobic power
induced by a strenuous program of endurance exercise. J Appl Physiol
Respir Environ Exerc Physiol. 1977;42(3):372–6. https://doi.org/10.1152/
jappl.1977.42.3.372.
65. Bacon AP, Carter RE, Ogle EA, Joyner MJ. Vo(2)max trainability and high
intensity interval training in humans: a meta-analysis. PLoS ONE.
2013;8(9):73182. https://doi.org/10.1371/journal.pone.0073182.
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Minerva Access is the Institutional Repository of The University of Melbourne
Author/s:
Prochilo, GA; Costa, RJS; Hassed, C; Chambers, R; Molenberghs, P
Title:
A 16-week aerobic exercise and mindfulness-based intervention on chronic psychosocial
stress: a pilot and feasibility study
Date:
2021-03-06
Citation:
Prochilo, G. A., Costa, R. J. S., Hassed, C., Chambers, R. & Molenberghs, P. (2021). A 16week aerobic exercise and mindfulness-based intervention on chronic psychosocial stress: a
pilot and feasibility study. PILOT AND FEASIBILITY STUDIES, 7 (1),
https://doi.org/10.1186/s40814-020-00751-6.
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http://hdl.handle.net/11343/273111
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