Thomas Barstow
Kansas State University, Kinesiology, Faculty Member
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PURPOSE: To determine oxygen uptake during three varying duration high-intensity functional training (HIFT) sessions. METHODS: Six healthy men with >1 year of HIFT experience were recruited (age:29±5 yrs). Participants completed an... more
PURPOSE: To determine oxygen uptake during three varying duration high-intensity functional training (HIFT) sessions. METHODS: Six healthy men with >1 year of HIFT experience were recruited (age:29±5 yrs). Participants completed an incremental exercise test on a treadmill to determine maximal oxygen consumption (VO2max), gas exchange threshold (GET), and respiratory compensation point (RCP). Participants completed three HIFT sessions. Session 1 (S1) consisted of 3 rounds of power cleans and ring dips. Session 2 (S2) consisted of 3 rounds of a 400-meter run, 21 kettlebell swings and 12 pull-ups. Session 3 (S3) consisted of as many rounds as possible of 5 pull-ups, 10 push-ups and 15 squats in 20 minutes. Participants were encourage to complete S1 and S2 as fast as possible, while performing as many repetitions as possible in S3. Pulmonary gas exchange (VO2, VCO2, VE) were measured during each session. RESULTS: The mean VO2max was 55.9±5.6 mL/kg/min with GET and RCP representing 61% and 79% of VO2max, respectively. The average time to complete S1 was 513±59s and elicited a mean %V̇O2max of 70±7% that was not different from GET or RCP (p>0.05). S2 required on average 783±79s to complete, with a mean %V̇O2max of 82±7% of V̇O2max that was significantly higher than GET (p<0.05), but not different compared to RCP (p>0.05). Mean %V̇O2max across S3 was 66±6%, however the average %V̇O2max was significantly higher than GET (p<0.05) at minutes 2-8, but not different at any other interval and was not different compared to RCP (p>0.05). Furthermore, V̇O2 demonstrated significant oscillations during all sessions (p<0.05). CONCLUSIONS: Participants with HIFT experience who completed sessions as quickly as possible or performed as many rounds as possible elicited an oxygen consumption from 66-82% of V̇O2max. Moreover, the oscillating V̇O2 during HIFT suggests that metabolic demands, which ranged from 46-92% of V̇O2max within-subjects, do not achieve a steady-state. Previous work suggests that the oscillating V̇O2 response could be a potent stimulus for improving health and fitness characteristics.
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Accelerometer data provide useful information about subject activity in many different application scenarios. For this study, single-accelerometer data were acquired from subjects participating in field tests that mimic tasks that... more
Accelerometer data provide useful information about subject activity in many different application scenarios. For this study, single-accelerometer data were acquired from subjects participating in field tests that mimic tasks that astronauts might encounter in reduced gravity environments. The primary goal of this effort was to apply classification algorithms that could identify these tasks based on features present in their corresponding accelerometer data, where the end goal is to establish methods to unobtrusively gauge subject well-being based on sensors that reside in their local environment. In this initial analysis, six different activities that involve leg movement are classified. The k-Nearest Neighbors (kNN) algorithm was found to be the most effective, with an overall classification success rate of 90.8%.
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Missions to terrestrial destinations (i.e., asteroids, the Moon, and Mars) will consist of physically challenging mission-critical tasks. These tasks, coupled with the negative physiological effects of prolonged microgravity exposure,... more
Missions to terrestrial destinations (i.e., asteroids, the Moon, and Mars) will consist of physically challenging mission-critical tasks. These tasks, coupled with the negative physiological effects of prolonged microgravity exposure, create a plausible situation in which physical requirements may exceed an astronaut&#39;s physical capacity. Therefore, the objective of the current study was to evaluate the association of aerobic fitness and muscular strength parameters with performance during two field tests designed to simulate upper-body mission-critical activities. There were 70 subjects who completed a material transport field test requiring the loading, transport, and unloading of geological samples and a device operations field test consisting of tasks associated with equipment set-up and the operations of controls and valves. The relationships between test duration and the following measurements were determined: running Vo(2max), gas exchange threshold (GET), speed at Vo(2max) (s-Vo(2max)), highest sustainable rate of aerobic metabolism [critical speed (CS)], and the finite distance that could be covered above CS (D&#39;); and arm cranking Vo(2peak), GET, critical power (CP), and the finite work that can be performed above CP (W&#39;). CP (r = -0.66), CS (r = -0.56), and arm cranking Vo(2peak) (r = -0.54) were most strongly correlated with the material transport field test and decision tree analysis revealed CP as the best predictor of performance. For the device operations field test, CP (r = -0.70), CS (r = -0.62), and arm cranking peak power output (r = -0.56) were significant predictors. Arm cranking tests are strongly associated with upper-body dependent tasks, highlighting that the nature of mission tasks needs to be considered when evaluating astronaut physical capacity.
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This study aimed to investigate the feasibility of determining the physiological parameters associated with the ability to complete simulated exploration type tasks at metabolic rates which might be expected for lunar and Martian... more
This study aimed to investigate the feasibility of determining the physiological parameters associated with the ability to complete simulated exploration type tasks at metabolic rates which might be expected for lunar and Martian ambulation. Running V̇O2max and gas exchange threshold (GET) were measured in 21 volunteers. Two simulated extravehicular activity field tests were completed in 1 G in regular athletic apparel at two intensities designed to elicit metabolic rates of ∼20.0 and ∼30.0 ml · kg(-1) · min(-1), which are similar to those previously reported for ambulation in simulated lunar- and Martian-based environments, respectively. All subjects were able to complete the field test at the lunar intensity, but 28% were unable to complete the field test at the Martian intensity (non-Finishers). During the Martian field test there were no differences in V̇O2 between Finishers and non-Finishers, but the non-Finishers achieved a greater %V̇O2max compared to Finishers (78.4 ± 4.6% vs. 64.9 ± 9.6%). Logistic regression analysis revealed fitness thresholds for a predicted probability of 0.5, at which Finishing and non-Finishing are equally likely, and 0.75, at which an individual has a 75% chance of Finishing, to be a V̇O2max of 38.4 ml · kg(-1) · min(-1) and 40.0 ml · kg(-1) · min(-1) or a GET of 20.1 ml · kg(-1) · min(-1) and 25.1 ml · kg(-1) · min(-1), respectively (χ(2) = 10.2). Logistic regression analysis also revealed that the expected %V̇O2max required to complete a field test could be used to successfully predict performance (χ(2) = 19.3). The results of the present investigation highlight the potential utility of V̇O2max, particularly as it relates to the metabolic demands of a surface ambulation, in defining successful completion of planetary-based exploration field tests.
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We tested the hypothesis that limb vascular conductance (LVC) would increase during the immediate recovery phase of dynamic exercise above, but not below, critical power (CP) indicating a threshold for muscular contraction-induced... more
We tested the hypothesis that limb vascular conductance (LVC) would increase during the immediate recovery phase of dynamic exercise above, but not below, critical power (CP) indicating a threshold for muscular contraction-induced impedance of limb blood flow (LBF). CP (115 ± 26 W) was determined in 7 men and 7 women who subsequently performed ∼5 min of near-supine cycling exercise both below and above CP. LVC demonstrated a greater increase during immediate recovery and remained significantly higher following exercise above, compared to below, CP (all p < 0.001). Power output was associated with the immediate increases in LVC following exercise above, but not below, CP (p < 0.001; r = 0.85). Additionally, variance in percent LBF impedance was significantly lower above (CV: 10.7 %), compared to below (CV: 53.2 %), CP (p < 0.01). CP appears to represent a threshold above which the characteristics of LBF impedance by muscular contraction become intensity-dependent. These data suggest a critical level of LBF impedance relative to contraction intensity exists and, once attained, may promote the progressive metabolic and neuromuscular responses known to occur above CP.
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New Findings What is the central question of this study? What are the characteristics of the time courses of blood flow in the brachial artery and microvascular beds of the skin and skeletal muscle following transient ischaemia? What is... more
New Findings What is the central question of this study? What are the characteristics of the time courses of blood flow in the brachial artery and microvascular beds of the skin and skeletal muscle following transient ischaemia? What is the main finding and its importance? Skeletal muscle blood flow was significantly slower than the transient increase in the cutaneous tissue, suggesting mechanistic differences between cutaneous and muscular blood flow distribution after transient ischaemia. These results challenge the use of the cutaneous circulation as globally representative of vascular function. Vascular function can be assessed by measuring post‐occlusion hyperaemic responses along the arterial tree (vascular occlusion test; VOT). It is currently unclear if responses are similar across vascular beds following cuff release, given potential differences in compliance. To examine this, we compared laser Doppler‐derived blood flux in the cutaneous circulation (LDFcut) and skeletal mu...
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Critical power represents an important threshold for neuromuscular fatigue development and may, therefore, dictate intensities for which exercise tolerance is determined by the magnitude of fatigue accrued. Peripheral fatigue appears to... more
Critical power represents an important threshold for neuromuscular fatigue development and may, therefore, dictate intensities for which exercise tolerance is determined by the magnitude of fatigue accrued. Peripheral fatigue appears to be constant across O2 delivery conditions for large muscle mass exercise, but this consistency is equivocal for smaller muscle mass exercise. We sought to determine the influence of blood flow occlusion during handgrip exercise on neuromuscular fatigue development and to examine the relationship between neuromuscular fatigue development and W '. Blood flow occlusion influenced the development of both peripheral and central fatigue, thus providing further evidence that the magnitude of peripheral fatigue is not constant across O2 delivery conditions for small muscle mass exercise. W ' appears to be related to the magnitude of fatigue accrued during exercise, which may explain the reported consistency of intramuscular metabolic perturbations an...
Research Interests: Physiology, Chemistry, Cardiology, Skeletal muscle biology, Medicine, and 15 moreBiological Sciences, Humans, Internal Medicine, Male, Young Adult, Exercise, Electromyography, Adult, Blood Flow, Muscle Fatigue, Exercise Test, Peripheral, Brachial artery, Medical and Health Sciences, and Hand strength
Research Interests: Chemistry, Animal Science, Medicine, Humans, Male, and 15 moreElectromyography, Hemoglobin, Medical Physiology, Adult, Time Factors, Muscle contraction, Exercise Test, Oxygen Consumption, Exercise Tolerance, Neurosciences, Hemoglobins, Duty Cycle, Cardiovascular medicine and haematology, ergometry, and Hand strength
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During exercise, less additional CO2 is stored per kilogram body weight in children than in adults, suggesting that children have a smaller capacity to store metabolically produced CO2. To examine this, tracer doses of [13C]bicarbonate... more
During exercise, less additional CO2 is stored per kilogram body weight in children than in adults, suggesting that children have a smaller capacity to store metabolically produced CO2. To examine this, tracer doses of [13C]bicarbonate were administered orally to 10 children (8-12 yr) and 12 adults (25-40 yr) at rest. Washout of 13CO2 in breath was analyzed to estimate recovery of tracer, mean residence time (MRT), and size of CO2 stores. CO2 production (VCO2) was also measured breath by breath using gas exchange techniques. Recovery did not differ significantly between children [73 +/- 13% (SD)] and adults (71 +/- 9%). MRT was shorter in children (42 +/- 7 min) compared with adults (66 +/- 15 min, P less than 0.001). VCO2 per kilogram was higher in the children (5.4 +/- 0.9 ml.min-1.kg-1) compared with adults (3.1 +/- 0.5, P less than 0.0001). Tracer estimate of CO2 production was correlated to VCO2 (r = 0.86, P less than 0.0001) and when corrected for mean recovery accurately pred...
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Research Interests: Chemistry, Kinetics, Medicine, Mammals, Humans, and 15 moreMale, Oxygen Uptake, Exercise, Medical Physiology, Adult, Pulmonary, Physical Exercise, Exercise Test, Oxygen Consumption, Neurosciences, Non linear regression, Pulmonary ventilation, Gas Exchange, Pulmonary Gas Exchange, and Cardiovascular medicine and haematology
Research Interests: Chemistry, Skeletal muscle biology, Kinetics, Respiratory Physiology, Medicine, and 15 moreHumans, Computer Simulation, Capillaries, Computer Model, Oxygen Uptake, Exercise, Medical Physiology, Skeletal Muscle, Oxygen, Theoretical Framework, Blood Flow, Music Information Dynamics, Oxygen Consumption, Neurosciences, and Cardiovascular medicine and haematology
Technical limitations have precluded measurement of the V(O(2)) profile within contracting muscle (mV(O(2))) and hence it is not known to what extent V(O(2)) dynamics measured across limbs in humans or muscles in the dog are influenced by... more
Technical limitations have precluded measurement of the V(O(2)) profile within contracting muscle (mV(O(2))) and hence it is not known to what extent V(O(2)) dynamics measured across limbs in humans or muscles in the dog are influenced by transit delays between the muscle microvasculature and venous effluent. Measurements of capillary red blood cell flux and microvascular P(O(2)) (P(O(2)m)) were combined to resolve the time course of mV(O(2)) across the rest-stimulation transient (1 Hz, twitch contractions). mV(O(2)) began to rise at the onset of contractions in a close to monoexponential fashion (time constant, J = 23.2 +/- 1.0 sec) and reached it&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s steady-state value at 4.5-fold above baseline. Using computer simulation in healthy and disease conditions (diabetes and chronic heart failure), our findings suggest that: (1) mV(O(2)) increases essentially immediately (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 2 sec) following exercise onset; (2) within healthy muscle the J blood flow (thus O(2) delivery, J Q(O(2)m)) is faster than JmV(O(2)) such that oxygen delivery is not limiting, and 3) a faster P(O(2)m) fall to a P(O(2)m) value below steady-state values within muscle from diseased animals is consistent with a relatively sluggish Q(O(2)m) response compared to that of mV(O(2)).
Research Interests: Mathematics, Chemistry, Kinetics, Microcirculation, Respiratory Physiology, and 15 moreMedicine, Computer Simulation, Animals, Oxygen Uptake, Medical Physiology, Rats, Myocardial Infarction, Chronic Heart Failure, Blood Flow, Muscle contraction, Red blood cell, Oxygen Consumption, Neurosciences, Cardiovascular medicine and haematology, and Electric stimulation
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Other than during sleep and contrived laboratory testing protocols, humans rarely exist in prolonged metabolic steady states; rather, they transition among different metabolic rates (V O2). The dynamic transition of V O2 (V O2 kinetics),... more
Other than during sleep and contrived laboratory testing protocols, humans rarely exist in prolonged metabolic steady states; rather, they transition among different metabolic rates (V O2). The dynamic transition of V O2 (V O2 kinetics), initiated, for example, at exercise onset, provides a unique window into understanding metabolic control. This brief review presents the state-of-the art regarding control of V O2 kinetics within the context of a simple model that helps explain the work rate dependence of V O2 kinetics as well as the effects of environmental perturbations and disease. Insights emerging from application of novel approaches and technologies are integrated into established concepts to assess in what circumstances O2 supply might exert a commanding role over V O2 kinetics, and where it probably does not. The common presumption that capillary blood flow dynamics can be extrapolated accurately from upstream arterial measurements is challenged. From this challenge, new complexities emerge with respect to the relationships between O2 supply and flux across the capillary-myocyte interface and the marked dependence of these processes on muscle fiber type. Indeed, because of interfiber type differences in O2 supply relative to V O2, the presence of much lower O2 levels in the microcirculation supplying fast-twitch muscle fibers, and the demonstrated metabolic sensitivity of muscle to O2, it is possible that fiber type recruitment profiles (and changes thereof) might help explain the slowing of V O2 kinetics at higher work rates and in chronic diseases such as heart failure and diabetes.
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We examined the ability of patients with spinal cord injury to undergo adaptations to chronic exercise training (cycle ergometry) invoked by functional electrical stimulation (FES) of the legs. Nine such patients performed incremental and... more
We examined the ability of patients with spinal cord injury to undergo adaptations to chronic exercise training (cycle ergometry) invoked by functional electrical stimulation (FES) of the legs. Nine such patients performed incremental and constant work rate exercise before and after exercise training. Exercise sessions averaged 2.1 +/- 0.4/wk, and consisted of 30 min/session of continuous FES recumbent cycling with increasing work rate as tolerated. Peak VO2 and peak work rate significantly improved with training. Peak VO2 was significantly correlated with peak heart rate both before and after training (r = 0.97 pre and 0.85 post, P &lt; 0.01 for both). The time course of the VO2, VCO2 and VE responses to constant-load exercise (unloaded cycling) and in recovery (mean response time MRT) were very long prior to training, and became significantly faster following training. However, there was no correlation between percentage improvement in either MRTon or MRToff for VO2 and the percentage increase in peak VO2. Exercise tolerance in these patients with spinal cord injury appears to be a direct function of the ability to increase heart rate. Further, exercise training can elicit significant improvements in both exercise tolerance and in gas exchange kinetics, even when performed only twice per week. However, these improvements may be accomplished by different mechanisms.
Research Interests: Kinetics, Spinal Cord Injury, Medicine, Functional Electrical Stimulation, Medicine Science, and 15 moreParaplegia, Humans, Male, Heart rate, Exercise, Cycling, Quadriplegia, Adult, Leg, Spinal Cord Injuries, Oxygen Consumption, Physical Education and training, Gas Exchange, Pulmonary Gas Exchange, and Electric stimulation
We investigated the effects of glycolytic and tricarboxylic acid cycle metabolic intermediates on myoglobin redox forms and meat colour stability. Eighteen combinations of malate (M), lactate (L), and pyruvate (P) were added to beef... more
We investigated the effects of glycolytic and tricarboxylic acid cycle metabolic intermediates on myoglobin redox forms and meat colour stability. Eighteen combinations of malate (M), lactate (L), and pyruvate (P) were added to beef Longissimus lumborum, Psoas major, and Semitendinosus muscle homogenates to study their effect on metmyoglobin formation during incubation at 25 degrees C. Changes in surface colour at 0, 2, 4, 8, and 12 h were evaluated by using reflecto-spectrophotometry [both L*, a*, and b* and wavelengths specific for metmyoglobin (MMb)]. Addition of M, L, and P alone or in combinations stabilized (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) L*, a*, and b* values and myoglobin redox forms in muscle homogenates; however, there was a trend for P to be least effective. At the 2% concentrations for the individual metabolites, L was most effective at retarding MMb formation in the Semitendinosus (M was intermediate and P was least effective), and M was most effective in the Psoas major and L. lumborum muscles (L was intermediate and P was least effective). Metmyoglobin was reduced most effectively with a combination of metabolites (M + L &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; M + P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; L + P). Enhancing meat with these metabolites can effectively extend colour life of post-rigor meat, apparently by providing more reducing conditions for myoglobin, thus increasing myoglobin redox form stability.
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We investigated the response of frequency-domain multidistance (FDMD) near-infrared (NIR) tissue oximetry for detecting absolute amounts of myoglobin (Mb) redox forms and their relationship to meat colour stability. Four packaging formats... more
We investigated the response of frequency-domain multidistance (FDMD) near-infrared (NIR) tissue oximetry for detecting absolute amounts of myoglobin (Mb) redox forms and their relationship to meat colour stability. Four packaging formats were used to create different blends of Mb redox forms and meat colours during display. Changes in surface colour and subsurface pigment forms during simulated display time (0, 2, 4, and 10d at 2°C) were evaluated using surface reflecto-spectrophotometry (both L∗a∗b∗ and specific wavelengths) and FDMD NIR tissue oximetry. Data for both methods of direct measurement of oxymyoglobin and deoxymyoglobin were strongly related and accounted for 86–94% of the display variation in meat colour. Indirect estimates of metmyoglobin ranged from r2=59–85%. It appears that NIR tissue oximetry has potential as a noninvasive, rapid method for the assessment of meat colour traits and may help improve our understanding of meat colour chemistry in post-rigor skeletal muscle.
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Research Interests: Cardiovascular disease, Exercise therapy, Medicine, Physical Therapy, Functional Electrical Stimulation, and 15 moreHumans, Male, Arm, Heart rate, Oxygen Uptake, Clinical Sciences, Middle Aged, Adult, Leg, Lactic Acid, Exercise Test, Oxygen Consumption, Aerobic Capacity, Combined Modality Therapy, and Exercise training
Near infrared spectroscopy (NIRS) is a noninvasive technique of monitoring tissue oxygen saturation by detecting changes in tissue absorbance of two wavelengths (850 and 760 nm) reflecting the relative oxygenation of hemoglobin and... more
Near infrared spectroscopy (NIRS) is a noninvasive technique of monitoring tissue oxygen saturation by detecting changes in tissue absorbance of two wavelengths (850 and 760 nm) reflecting the relative oxygenation of hemoglobin and myoglobin. Aim of the present study was to determine whether changes in skeletal muscle oxygen saturation during incremental exercise detected by NIRS can reflect an impared oxygen delivery and an early onset of anaerobic metabolism in patients with chronic heart failure (CHF). We studied 19 subjects (mean age 43 +/- 16 years). Seven patients had a history of CHF with a diagnosis of ischemic cardiomyopathy (Group A) and 12 were healthy sedentary (Group B). All patients had a history of dyspnea on exertion (NY-HA II), peripheral edema, pulmonary rales and cardiac gallop sounds over the last 6 months. They were in sinus rhythm and stable clinical condition in the last 3 months. They were well matched regarding age, sex and body surface area. All subjects pe...