OpvoedkundeSportwetenskapPlease help us populate SUNScholar with the post print version of this a... more OpvoedkundeSportwetenskapPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: scholar@sun.ac.z
The purpose of this study was to examine fatigue effects on symmetry and stability during a maxim... more The purpose of this study was to examine fatigue effects on symmetry and stability during a maximal effort running time-trial m). Recreational runners had continuous recordings of 3D trunk acceleration parameters (spatio-temporal, RMS vector ratio, step symmetry, and stride regularity) during the lT. Statistical analysis was carried out using generalised estimating equations (GEE) to investigate longitudinal changes (laps two to eight) compared to baseline (lap one), while statistically adjusting for running speed. Runners had significantly longer contact times (4m lap onwards), higher mediolateral root mean square (RMS) ratio (3d lap onwards), lower vertical symmetry and vertical RMS ratio (final lap). Coaches could use these results to recognize, minimize, and delay fatigue related onset of asymmetries and instabilities possibly through training strategies.
International Journal of Sports Physiology and Performance, 2020
Purpose: To provide a systematic overview of physiological parameters used to determine the train... more Purpose: To provide a systematic overview of physiological parameters used to determine the training status of a trail runner and how well these parameters correlate with real-world trail running performance. Method: An electronic literature search of the PubMed and Scopus digital databases was performed. Combinations of the terms “trail run” or “trail runner” or “trail running” and “performance” were used as search terms. Seven studies met the inclusion criteria. Results: Trail running performance most commonly correlated (mean [SD]) with maximal aerobic capacity (71%; r = −.50 [.32]), lactate threshold (57%; r = −.48 [.28]), velocity at maximal aerobic capacity (43%; r = −.68 [.08]), running economy (43%; r = −.31 [.22]), body fat percentage (43%; r = .55 [.21]), and age (43%; r = .52 [.14]). Regression analyses in 2 studies were based on a single variable predicting 48% to 60% of performance variation, whereas 5 studies included multiple variable regression analyses predicting 48...
Small wireless trunk accelerometers have become a popular approach to unobtrusively quantify huma... more Small wireless trunk accelerometers have become a popular approach to unobtrusively quantify human locomotion and provide insights into both gait rehabilitation and sports performance. However, limited evidence exists as to which trunk accelerometry measures are suitable for the purpose of detecting movement compensations while running, and specifically in response to fatigue. The aim of this study was therefore to detect deviations in the dynamic center of mass (CoM) motion due to running-induced fatigue using tri-axial trunk accelerometry. Twenty runners aged 18-25 years completed an indoor treadmill running protocol to volitional exhaustion at speeds equivalent to their 3.2 km time trial performance. The following dependent measures were extracted from tri-axial trunk accelerations of 20 running steps before and after the treadmill fatigue protocol: the tri-axial ratio of acceleration root mean square (RMS) to the resultant vector RMS, step and stride regularity (autocorrelation procedure), and sample entropy. Running-induced fatigue increased mediolateral and anteroposterior ratios of acceleration RMS (p < .05), decreased the anteroposterior step regularity (p < .05), and increased the anteroposterior sample entropy (p < .05) of trunk accelerometry patterns. Our findings indicate that treadmill running-induced fatigue might reveal itself in a greater contribution of variability in horizontal plane trunk accelerations, with anteroposterior trunk accelerations that are less regular from step-to-step and are less predictable. It appears that trunk accelerometry parameters can be used to detect deviations in dynamic CoM motion induced by treadmill running fatigue, yet it is unknown how robust or generalizable these parameters are to outdoor running environments.
South African Journal for Research in Sport Physical Education and Recreation, 2003
The purpose of this study was to develop a questionnaire that measures the assertiveness of netba... more The purpose of this study was to develop a questionnaire that measures the assertiveness of netball players. The identification of typical characteristics and assessment by experts regarding the correctness and technical presentation of the items resulted in a preliminary questionnaire. The item analysis for the reduction of items took place by applying the homogeneity approach and the correlation of the score of each item with the total score. Ninety-two senior netball players participated in the major phase of this study. The players completed the preliminary questionnaire on assertiveness as well as the South African Personality Questionnaire that served as criterion measure for establishing the validity of the final form of 22-items. Internal consistency reliability was determined by means of the split-half-method. Both the reliability (r = 0.834) and validity (r = 0.297; p < 0.01) of the instrument proved to be satisfactory. It was concluded that this questionnaire is suitable for use in a netball setting.
Medicine and Science in Sports and Exercise, Jun 1, 2013
Limited data exists on a transition process of minimalist shoe running, warranting longitudinally... more Limited data exists on a transition process of minimalist shoe running, warranting longitudinally designed studies. The primary aim of this study was thus to determine whether lower limb kinematics can be adapted, whether vertical average loading rate (VALR) can be attenuated, and whether lower limb joint moments can be altered by either novice or short-term (seven-week) minimalist shoe training. Ten experimental (EXP) habitually shod male endurance runners (age 24.10 ± 1.74; weekly training mileage 29.36 ± 8.51 km; BMI: 22.83 ± 8.55 kg/m 2) volunteered to participate in a seven-week minimalist shoe transition programme. Eleven age and training matched control participants (CONT) (age 24.00 ± 2.18; weekly training mileage 24.90 ± 3.30 km; BMI: 23.78 ± 6.12) continued to run in their usual running shoes during the intervention period. All participants were provided with a pair of Vibram Fivefingers ® (VF). The VF intervention started at ~ 11% to 22% and ended at ~ 52% to 132% of the participants' usual shod training distance, determined by subjective lower limb comfort ratings. Lower limb biomechanics for barefoot: BF, minimalist: VF, and shod: SH were recorded with an eightcamera Vicon ® motion capture system, synchronized with a Bertec ® force plate, both prior to and after the transition programme. Twelve running trials at self-selected speeds were recorded bilaterally for each shoe condition. An inverse dynamic approach was used to calculate lower extremity joint moments. Primary parameters of interest were kinematic: step frequency (steps/min), step length (m), footstrike angles (FSA, degrees), strike index (SI,%); average vertical loading rate (VALR, BW/S) and sagittal and frontal plane peak joint moments (Nm/kg.m) of the ankle, knee and hip. At pre-testing, the results showed that for VALR, VF running was significantly higher than SH running but significantly lower than BF running (P < 0.05). Statistically significant shorter step lengths, higher step frequencies, greater plantar-flexion FSA, higher strike index, greater knee flexion FSA, and greater ankle inversion FSA were seen in BF and VF conditions compared to SH (P < 0.05). Stellenbosch University http://scholar.sun.ac.za v Statistically higher plantarflexion moment peak (PFM) while lower ankle dorsiflexion moment peak (DFM) and knee abduction moment peak (KAM) was found while BF and VF than SH running. The only statistically significant effect of the VF training intervention on kinematics was that of higher step frequency for the SH condition (P < 0.05), and greater inversion FSA in the BF condition. A trend was seen for the EXP group to increase VALR (P > 0.05). Ankle PFM peak significantly increased, while knee extensor moment peak (KEM) peak significantly decreased for the EXP group only (P < 0.05). Contrary to the initial hypothesis, novice or short-term VF training did not result in significantly attenuated VALR. However, alterations in joint moments suggest a shift in the distribution of external loads due to the VF training. Insufficient kinematic adaptation with VF training could be attributed to inability to sense higher VALR or due to greater perceived ratings of calf-Achilles discomfort, and may indicate that more than seven-weeks are required to transition and adapt to VF running.
The purpose of this study was to investigate if trunk accelerometry measures were influenced by o... more The purpose of this study was to investigate if trunk accelerometry measures were influenced by outdoor surface while running. A sample of highly-trained (n=12) and recreational (n=17) ran on three independent surfaces, namely asphalt, synthetic track, and wood-chip. Dependent accelerometry measures were step frequency (S FREQ), step symmetry (S SYM), stride regularity (S REG), axis contribution to total amplitude (RMS RATIO) and sample entropy (S EN). Surface effects on accelerometry measures were consistent for both running groups. Several significant differences existed between wood-chip and either asphalt or synthetic track. The results suggest that surface specific considerations should be made when quantifying trunk accelerometry measures related to running gait symmetry and regularity during running.
Changes in oxygen cost per a given distance of running due to fatigue have often been accompanied... more Changes in oxygen cost per a given distance of running due to fatigue have often been accompanied with alterations in running kinematics. Nevertheless, it is not certain if the changes in the oxygen cost of transport are as a result of the fatigue or the modifications in the kinematics. We, therefore, sought to understand the correlations between changes in running kinematics and oxygen cost of transport in fatigued running. Thirty-two recreational (16 men, 16 women) runners underwent a fatigue protocol which involved incremental speed to volitional exhaustion on a motorized treadmill, whiles heart rate, oxygen consumption, blood lactate, and RPE were monitored. Spatio-temporal kinematic data was assessed with an Optogait photoelectric system, and GoPro Hero 4 Black camera was used to capture upper extremity kinematics for offline analysis. Changes in pre-and post-fatigue and the interactions between the changes in kinematic parameters and oxygen cost of transport were assessed. For...
Maintaining stability under dynamic conditions is an inherent challenge to bipedal running. This ... more Maintaining stability under dynamic conditions is an inherent challenge to bipedal running. This challenge may impose an energetic cost (Ec) thus hampering endurance running performance, yet the underlying mechanisms are not clear. Wireless triaxial trunk accelerometry is a simple tool that could be used to unobtrusively evaluate these mechanisms. Here, we test a cost of instability hypothesis by examining the contribution of trunk accelerometry-based measures (triaxial root mean square, step and stride regularity, and sample entropy) to interindividual variance in Ec (J/m) during treadmill running. Accelerometry and indirect calorimetry data were collected concurrently from 30 recreational runners (16 men; 14 women) running at their highest steady-state running speed (80.65 ± 5.99% V̇o2max). After reducing dimensionality with factor analysis, the effect of dynamic stability features on Ec was evaluated using hierarchical multiple regression analysis. Three accelerometry-based measu...
OpvoedkundeSportwetenskapPlease help us populate SUNScholar with the post print version of this a... more OpvoedkundeSportwetenskapPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: scholar@sun.ac.z
South African Journal for Research in Sport, Physical Education and Recreation
Please help populate SUNScholar with the full text of SU research output. Also - should you need ... more Please help populate SUNScholar with the full text of SU research output. Also - should you need this item urgently, please send us the details and we will try to get hold of the full text as quick possible. E-mail to scholar@sun.ac.za. Thank you.Journal Articles (subsidised)Geneeskunde en GesondheidswetenskappeFisioterapi
OpvoedkundeSportwetenskapPlease help us populate SUNScholar with the post print version of this a... more OpvoedkundeSportwetenskapPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: scholar@sun.ac.z
The purpose of this study was to examine fatigue effects on symmetry and stability during a maxim... more The purpose of this study was to examine fatigue effects on symmetry and stability during a maximal effort running time-trial m). Recreational runners had continuous recordings of 3D trunk acceleration parameters (spatio-temporal, RMS vector ratio, step symmetry, and stride regularity) during the lT. Statistical analysis was carried out using generalised estimating equations (GEE) to investigate longitudinal changes (laps two to eight) compared to baseline (lap one), while statistically adjusting for running speed. Runners had significantly longer contact times (4m lap onwards), higher mediolateral root mean square (RMS) ratio (3d lap onwards), lower vertical symmetry and vertical RMS ratio (final lap). Coaches could use these results to recognize, minimize, and delay fatigue related onset of asymmetries and instabilities possibly through training strategies.
International Journal of Sports Physiology and Performance, 2020
Purpose: To provide a systematic overview of physiological parameters used to determine the train... more Purpose: To provide a systematic overview of physiological parameters used to determine the training status of a trail runner and how well these parameters correlate with real-world trail running performance. Method: An electronic literature search of the PubMed and Scopus digital databases was performed. Combinations of the terms “trail run” or “trail runner” or “trail running” and “performance” were used as search terms. Seven studies met the inclusion criteria. Results: Trail running performance most commonly correlated (mean [SD]) with maximal aerobic capacity (71%; r = −.50 [.32]), lactate threshold (57%; r = −.48 [.28]), velocity at maximal aerobic capacity (43%; r = −.68 [.08]), running economy (43%; r = −.31 [.22]), body fat percentage (43%; r = .55 [.21]), and age (43%; r = .52 [.14]). Regression analyses in 2 studies were based on a single variable predicting 48% to 60% of performance variation, whereas 5 studies included multiple variable regression analyses predicting 48...
Small wireless trunk accelerometers have become a popular approach to unobtrusively quantify huma... more Small wireless trunk accelerometers have become a popular approach to unobtrusively quantify human locomotion and provide insights into both gait rehabilitation and sports performance. However, limited evidence exists as to which trunk accelerometry measures are suitable for the purpose of detecting movement compensations while running, and specifically in response to fatigue. The aim of this study was therefore to detect deviations in the dynamic center of mass (CoM) motion due to running-induced fatigue using tri-axial trunk accelerometry. Twenty runners aged 18-25 years completed an indoor treadmill running protocol to volitional exhaustion at speeds equivalent to their 3.2 km time trial performance. The following dependent measures were extracted from tri-axial trunk accelerations of 20 running steps before and after the treadmill fatigue protocol: the tri-axial ratio of acceleration root mean square (RMS) to the resultant vector RMS, step and stride regularity (autocorrelation procedure), and sample entropy. Running-induced fatigue increased mediolateral and anteroposterior ratios of acceleration RMS (p < .05), decreased the anteroposterior step regularity (p < .05), and increased the anteroposterior sample entropy (p < .05) of trunk accelerometry patterns. Our findings indicate that treadmill running-induced fatigue might reveal itself in a greater contribution of variability in horizontal plane trunk accelerations, with anteroposterior trunk accelerations that are less regular from step-to-step and are less predictable. It appears that trunk accelerometry parameters can be used to detect deviations in dynamic CoM motion induced by treadmill running fatigue, yet it is unknown how robust or generalizable these parameters are to outdoor running environments.
South African Journal for Research in Sport Physical Education and Recreation, 2003
The purpose of this study was to develop a questionnaire that measures the assertiveness of netba... more The purpose of this study was to develop a questionnaire that measures the assertiveness of netball players. The identification of typical characteristics and assessment by experts regarding the correctness and technical presentation of the items resulted in a preliminary questionnaire. The item analysis for the reduction of items took place by applying the homogeneity approach and the correlation of the score of each item with the total score. Ninety-two senior netball players participated in the major phase of this study. The players completed the preliminary questionnaire on assertiveness as well as the South African Personality Questionnaire that served as criterion measure for establishing the validity of the final form of 22-items. Internal consistency reliability was determined by means of the split-half-method. Both the reliability (r = 0.834) and validity (r = 0.297; p < 0.01) of the instrument proved to be satisfactory. It was concluded that this questionnaire is suitable for use in a netball setting.
Medicine and Science in Sports and Exercise, Jun 1, 2013
Limited data exists on a transition process of minimalist shoe running, warranting longitudinally... more Limited data exists on a transition process of minimalist shoe running, warranting longitudinally designed studies. The primary aim of this study was thus to determine whether lower limb kinematics can be adapted, whether vertical average loading rate (VALR) can be attenuated, and whether lower limb joint moments can be altered by either novice or short-term (seven-week) minimalist shoe training. Ten experimental (EXP) habitually shod male endurance runners (age 24.10 ± 1.74; weekly training mileage 29.36 ± 8.51 km; BMI: 22.83 ± 8.55 kg/m 2) volunteered to participate in a seven-week minimalist shoe transition programme. Eleven age and training matched control participants (CONT) (age 24.00 ± 2.18; weekly training mileage 24.90 ± 3.30 km; BMI: 23.78 ± 6.12) continued to run in their usual running shoes during the intervention period. All participants were provided with a pair of Vibram Fivefingers ® (VF). The VF intervention started at ~ 11% to 22% and ended at ~ 52% to 132% of the participants' usual shod training distance, determined by subjective lower limb comfort ratings. Lower limb biomechanics for barefoot: BF, minimalist: VF, and shod: SH were recorded with an eightcamera Vicon ® motion capture system, synchronized with a Bertec ® force plate, both prior to and after the transition programme. Twelve running trials at self-selected speeds were recorded bilaterally for each shoe condition. An inverse dynamic approach was used to calculate lower extremity joint moments. Primary parameters of interest were kinematic: step frequency (steps/min), step length (m), footstrike angles (FSA, degrees), strike index (SI,%); average vertical loading rate (VALR, BW/S) and sagittal and frontal plane peak joint moments (Nm/kg.m) of the ankle, knee and hip. At pre-testing, the results showed that for VALR, VF running was significantly higher than SH running but significantly lower than BF running (P < 0.05). Statistically significant shorter step lengths, higher step frequencies, greater plantar-flexion FSA, higher strike index, greater knee flexion FSA, and greater ankle inversion FSA were seen in BF and VF conditions compared to SH (P < 0.05). Stellenbosch University http://scholar.sun.ac.za v Statistically higher plantarflexion moment peak (PFM) while lower ankle dorsiflexion moment peak (DFM) and knee abduction moment peak (KAM) was found while BF and VF than SH running. The only statistically significant effect of the VF training intervention on kinematics was that of higher step frequency for the SH condition (P < 0.05), and greater inversion FSA in the BF condition. A trend was seen for the EXP group to increase VALR (P > 0.05). Ankle PFM peak significantly increased, while knee extensor moment peak (KEM) peak significantly decreased for the EXP group only (P < 0.05). Contrary to the initial hypothesis, novice or short-term VF training did not result in significantly attenuated VALR. However, alterations in joint moments suggest a shift in the distribution of external loads due to the VF training. Insufficient kinematic adaptation with VF training could be attributed to inability to sense higher VALR or due to greater perceived ratings of calf-Achilles discomfort, and may indicate that more than seven-weeks are required to transition and adapt to VF running.
The purpose of this study was to investigate if trunk accelerometry measures were influenced by o... more The purpose of this study was to investigate if trunk accelerometry measures were influenced by outdoor surface while running. A sample of highly-trained (n=12) and recreational (n=17) ran on three independent surfaces, namely asphalt, synthetic track, and wood-chip. Dependent accelerometry measures were step frequency (S FREQ), step symmetry (S SYM), stride regularity (S REG), axis contribution to total amplitude (RMS RATIO) and sample entropy (S EN). Surface effects on accelerometry measures were consistent for both running groups. Several significant differences existed between wood-chip and either asphalt or synthetic track. The results suggest that surface specific considerations should be made when quantifying trunk accelerometry measures related to running gait symmetry and regularity during running.
Changes in oxygen cost per a given distance of running due to fatigue have often been accompanied... more Changes in oxygen cost per a given distance of running due to fatigue have often been accompanied with alterations in running kinematics. Nevertheless, it is not certain if the changes in the oxygen cost of transport are as a result of the fatigue or the modifications in the kinematics. We, therefore, sought to understand the correlations between changes in running kinematics and oxygen cost of transport in fatigued running. Thirty-two recreational (16 men, 16 women) runners underwent a fatigue protocol which involved incremental speed to volitional exhaustion on a motorized treadmill, whiles heart rate, oxygen consumption, blood lactate, and RPE were monitored. Spatio-temporal kinematic data was assessed with an Optogait photoelectric system, and GoPro Hero 4 Black camera was used to capture upper extremity kinematics for offline analysis. Changes in pre-and post-fatigue and the interactions between the changes in kinematic parameters and oxygen cost of transport were assessed. For...
Maintaining stability under dynamic conditions is an inherent challenge to bipedal running. This ... more Maintaining stability under dynamic conditions is an inherent challenge to bipedal running. This challenge may impose an energetic cost (Ec) thus hampering endurance running performance, yet the underlying mechanisms are not clear. Wireless triaxial trunk accelerometry is a simple tool that could be used to unobtrusively evaluate these mechanisms. Here, we test a cost of instability hypothesis by examining the contribution of trunk accelerometry-based measures (triaxial root mean square, step and stride regularity, and sample entropy) to interindividual variance in Ec (J/m) during treadmill running. Accelerometry and indirect calorimetry data were collected concurrently from 30 recreational runners (16 men; 14 women) running at their highest steady-state running speed (80.65 ± 5.99% V̇o2max). After reducing dimensionality with factor analysis, the effect of dynamic stability features on Ec was evaluated using hierarchical multiple regression analysis. Three accelerometry-based measu...
OpvoedkundeSportwetenskapPlease help us populate SUNScholar with the post print version of this a... more OpvoedkundeSportwetenskapPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: scholar@sun.ac.z
South African Journal for Research in Sport, Physical Education and Recreation
Please help populate SUNScholar with the full text of SU research output. Also - should you need ... more Please help populate SUNScholar with the full text of SU research output. Also - should you need this item urgently, please send us the details and we will try to get hold of the full text as quick possible. E-mail to scholar@sun.ac.za. Thank you.Journal Articles (subsidised)Geneeskunde en GesondheidswetenskappeFisioterapi
Uploads
Papers by Ranel Venter