Biomedical subjects

J D Rouillon

Publications and source records attributed to J D Rouillon.

At least 19 recordsLinked to original sources

PubMed2003

Effects of a wheelchair ergometer training programme on spinal cord-injured persons.

STUDY DESIGN: Before and after investigation of the effects of a wheelchair ergometer Training programme. OBJECTIVE: To investigate the effects of an original interval-training programme on work capacity and cardiorespiratory variables with spinal cord-injured persons (SCIP's) on a wheelchair-specific ergometer. SETTING: BESANCON, FRANCE. METHODS: Seven SCIP's (male) performed 45 min of wheelchair ergometry three times per week, for 6 weeks. Training effects on maximal dynamic performance and endurance capacity were studied by comparison of performance and cardiorespiratory responses observed during both a maximal progressive test (10 W/2 min) and the same training session performed before and after training. RESULTS: Training induced significant improvements in maximal tolerated power (+19.6%), in peak oxygen consumption (VO2,+16%), and in oxygen pulse (O2p,+18.7%). At ventilatory threshold, significant improvements were also observed in power output (+63%), VO2VT(+ 34.1), ventilation VEVT(+ 37.1%), and V2pVT(+ 19.9% ). Heart rate and ventilation were significantly lower (-11 and -14.6%, respectively) after training at the same work rate, while VO2 was unchanged. Between the first and the last training session, the total physical work was improved by 24.7%, whereas heart rate was unchanged. CONCLUSION: An interval-training programme individualised to each paraplegic subject using a wheelchair ergometer can significantly improve the fitness level and endurance capacity.

Adult↗

PubMed2003

Physiological and metabolic responses of triathletes to a simulated 30-min time-trial in cycling at self-selected intensity.

The aim of this study was to investigate the metabolic and physiological responses to a laboratory-based simulated 30-min individual time-trial (ITT 30 ) in cycling at a self-selected intensity. Twelve experienced triathletes (n = 4 women) performed a progressive incremental exercise test on a cycle ergometer to determine .VO2max (52 +/- 5 ml x min -1 x kg -1), maximum power output (300 +/- 12 W), and the second ventilatory threshold. Then, the subjects completed an ITT30 at self-selected work intensity on a stationary ergometer equipped with the SRM Training System. In all subjects, during the ITT30, heart rate and minute ventilation increased (p < 0.05) progressively whereas oxygen consumption and power output remained unchanged. Triathletes rode at consistent pacing corresponding to their highest steady state of blood lactate concentration that increased by no more than 1.0 mmol x l -1 during the final 20-min of ITT30. The self-selected intensity of triathletes during ITT30 represented 88 +/- 5 % (mean +/- SD) of .VO2max and was not significantly different to the energy demand corresponding to the second ventilatory threshold (84 +/- 5 % of .VO2max). Our data suggest that ITT 30 at a self-selected intensity is a good predictor of individual endurance capacity and may be used to estimate racing pace for training purposes. This performance test for the identification of the exercise intensity that demarcate "steady state" is less troublesome than some of the traditional methods, limiting testing to a single session.

Adult↗

PubMed2002

Influence of the age on self regulation of static grip forces from perceived exertion values.

The investigation of self-regulation of grip force provides indirect cues about the developmental neurobiology of the subject. The aim of this study was to examine the ability of subjects of different ages to produce different forces based on their perceived exertion during a grip force task by using a test and a randomised re-test procedure. Eighteen young children (aged 6.5 years), 18 adolescents (13.5 years) and 18 adults (28.5 years) performed a graded hand grip strength test (GST) at four intensities. Perceived exertion (RPE-C) was recorded at the end of each load level. Then, subjects were scheduled for a randomised grip strength test performed in the same experimental conditions than GST. Statistical analysis revealed no significant effect in grip strength for test in the three groups. However, a significant main effect for intensities was obtained in the three groups (P < 0.0001). Significant correlations were observed between GST and RPE-C (r(2) = 0.62, P < 0.0001; r(2) = 0.53, P < 0.0001; r(2) = 0.51, P < 0.0001), in the children, adolescent and adult groups, respectively. However at low grip force intensities, it appears that children have some difficulties to rate their perceived exertion. The results of this study suggest that the neurodevelopmental level of 6-year-old children do not affect the ability to produce reliably moderate to intense forces from perceived exertion during a grip force task.

Adolescent↗

PubMed2002

Perceived exertion and rehabilitation with wheelchair ergometer: comparison between patients with spinal cord injury and healthy subjects.

OBJECTIVES: The purpose of this study was to compare the effects of a rehabilitation program on the perceived exertion (PE) and the cardioventilatory responses during exercise in healthy people and paraplegics. METHODS: A group of seven healthy persons (age 26.6 SD 6.2 years) and one of seven paraplegics (age 42 SD 15.9 years) participated in a rehabilitation program composed of Square Wave Exercise Tests (SWEET) during six weeks. The maximal oxygen uptake, the power output (PO), heart rate (HR) and measures of PE using the Borg CR 10 scale were investigated during a maximal graded test performed before and after the rehabilitation program. During the first SWEET session (SWEET 1) measures of PE and HR (base and peak) were also investigated and compared to the last session (SWEET 2) of the same absolute workload after the 6 weeks. RESULTS: Statistical analysis revealed no significant difference in both groups for PE between the two maximal graded tests. However, a significant decrease in the PE values (P<0.01) was observed in both groups during the SWEET 2. There was no significant difference in maximal HR between the two graded tests, but a significant decrease in HR (P<0.0001 for base HR and P<0.001 for peak HR) was observed in SWEET 2 compared to 1. The maximal tolerated power (MTP) and the peak oxygen uptake increased significantly in both healthy and paraplegic groups (P<0.0001 and P<0.05 respectively) after the 6 weeks of rehabilitation exercise. CONCLUSION: The results of the present study suggest that PE could be used to control the exercise intensity during a rehabilitation training program for paraplegics, similar to healthy subjects. The increase in the peak oxygen uptake and MTP demonstrates the positive effects of the rehabilitation program on the physical fitness of the subjects.

Adult↗

PubMed2002

Modelling the transfers of training effects on performance in elite triathletes.

This study investigated the effects of 40-weeks training in swimming, cycling and running on performances in swimming, running and triathlon competitions in four elite triathletes. The training stimulus was calculated using the exercise heart rate. The level of performance was measured in running by a submaximal 30 min run, in swimming by a 5 x 400 m all-out test and subjectively in triathlon competitions. A mathematical model using one to three first order transfer functions linked actual and modelled performances by minimizing the residual sum of squares between them. The relationships between training and performances were significant in running (tau(1) = 20; tau(2) = 10; r = 0.74; p < 0.001) and in swimming (tau(1) = 31; r = 0.37; p = 0.03), supporting the principle of specificity of the training loads. Cross-transfer training effects were identified between cycling and running (tau(1 = )42; r = 0.56; p < 0.001), but not with swimming performances. In addition, the training loads completed in running were shown to have a major effect on performances in triathlon competition (tau(1 = )52; tau(2 = )4; r = 0.52; p < 0.001), indicating that running training is an essential part of triathlon performance. Swimming appears to be a highly specific activity, which does not gain nor provide benefits from/to other activities (i. e. cycling and running). The present study shows that cross-transfer training effects occur between cycling training and running performance in elite triathletes. A similar cross-training effect does not seem to occur for swimming performance.

Adaptation, Physiological↗

PubMed2002

Relationships between aerobic energy cost, performance and kinematic parameters in roller ski skating.

The aims of this study were to test the hypotheses that 1) the aerobic energy cost of roller ski skating (CS) is significantly related to level of performance and 2) a significant part of inter-individual differences of CS can be explained by kinematic parameters of skating locomotion. Oxygen uptake, kinematics of the knee and ankle joint, EMG of the vastus lateralis (VL) and gastrocnemius lateralis (GL) muscles, and roller ski velocity were recorded in 13 skiers who roller skied at 19.0 +/- 0.1 km x h(-1). CS was found to be 2.51 +/- 0.35 J x kg(-1) x m(-1) and significantly correlated with the skiers' level of performance (r = 0.61; p < 0.05). Significant relationships were found between CS and 1) knee angular amplitude (r = 0.75; p < 0.01) during the concentric phase, 2) VL average EMG during the concentric phase (r = 0.72; p < 0.01) and 3) VL and GL average EMG during the eccentric phase (p < 0.05). The results of this study showed that a significant part of performance could be explained by the aerobic energy cost of locomotion in skating. It can also be suggested that differences in upper/lower body utilization and/or in mechanical efficiency may explain the differences in CS.

Adult↗

PubMed2002

Decrease in oxygen uptake at the end of a high-intensity submaximal running in humans.

The purpose of the present study was to examine oxygen consumption (VO(2) ) kinetics during severe-intensity running exercise through a four-phase model that considered a decrease in VO(2) at the end of the exercise in light of previous research in which this decrease was only noticed. After determination of maximal oxygen consumption VO(2) max), thirteen highly trained males performed a square-wave running to exhaustion at approximately 95 % of VO(2) max on a level treadmill. VO(2) and ventilatory gas exchange variables were determined breath-by-breath. Computerised non-linear regression techniques incorporating exponential and linear terms were used to describe VO(2) and ventilatory gas exchange variable responses. In contrast with the classical 3-component model that describes the increase in VO(2) for severe-intensity exercise, we observed a 4(th) phase characterised by a significant decrease in VO(2) before exhaustion (slope of VO(2)-time relationship significantly different from a zero value, p < 0.01) in 7 out of 13 subjects. Following a time delay of 31 +/- 44 s after the decrease in VO(2), a significant decrease of minute ventilation (V(E)) was present for 6 of the 7 subjects (p < 0.02). During the exercise for the subjects who decreased V(E), a reduction of 288 +/- 169 ml in tidal volume was associated with an increase of 10.2 +/- 2.4 min(-1) in breathing frequency. These data suggest that the respiratory system might be stressed more for some endurance-trained athletes. The specific link between reduced VO(2) and reduced V(E) remains to be explored.

Adolescent↗

PubMed2002

Recovery kinetics of oxygen uptake following severe-intensity exercise in runners.

BACKGROUND: This investigation sought to characterise the oxygen uptake (VO2) off-transient kinetics from severe exercise and to clarify discrepancies between on- and off-transient kinetics for VO2 seen in humans. METHODS: Eleven competitive endurance athletes underwent treadmill running until exhaustion at work-rates corresponding to the speed that elicited approximately 95% of maximal VO2. Gas exchange variables were determined breath-by-breath. Computerised non-linear regression techniques were used to fit the VO2 on- and off-transient kinetics. A 3-exponential model described the VO2 on-transient. VO2 off-transient was analysed to each response time course using 3 different models: a single-exponential model for the entire period and 2 3-exponential models where exponential terms starting either together after a common time delay or after independent time delays. RESULTS: Both 3-exponential models provided an excellent fit (r2>0.90) to the off-transient data. Compared with on-transient, VO2 off-transient kinetics was associated with a slower primary phase (time constant: 16+/-4 vs 39+/-13 sec, p<0.01) but was similar both in time delay and amplitude. CONCLUSIONS: These data indicate that there is no general symmetry between the exercise and recovery kinetics for VO2 because the response of the primary phase of VO2 off-transient resolves to a greater time constant, reflecting altered tissue metabolism. However, the mechanism(s) for the slow component is slow both in developing and to recover within the severe exercise domain.

Adult↗

PubMed2001

Interval training program on a wheelchair ergometer for paraplegic subjects.

BACKGROUND: Various combinations of training intensity, duration and frequency are often proposed to people with spinal cord injuries in order to improve their fitness. However, no consensus about a specific training program has been reached for such a population. OBJECTIVE: This study investigated the effects of a short interval training program specifically designed for patients with spinal cord injuries. METHODS: Paraplegic men performed 30-min wheelchair ergometry three times per week, for 4 weeks. Maximal dynamic performance and endurance capacity were studied before and after the training program with an incremental test (10 W/2 min) until volitional fatigue and a constant work rate test, respectively. Cardiorespiratory responses were continuously studied during each of these tests. RESULTS: Training induced significant improvement in maximal tolerated power (+27.9%), and in peak oxygen consumption ([VO2, +18.5%). After training the subjects were able to maintain the load applied during the constant test (total mechanical work +210.7%), for a significantly longer time. The heart rate, [VO2 and ventilation values observed when the volunteers ended their first constant load test were significantly higher (+10%, +10%, +40% respectively) than those obtained after a similar time period during the second constant load test which was performed after the training program. CONCLUSION: After this short training period, with an appropriate combination of different types of training, duration, intensity and frequency exercises, we observed a significant improvement in the fitness level and endurance capacity of paraplegic subjects.

Adult↗

PubMed2001

Validation of a rating scale of perceived exertion in young children.

The aim of this study was to develop and validate a scale rating the perceived exertion of young children (RPE-C) who do not read. This scale presents seven pictures showing a man who becomes progressively fatigued. In order to evaluate this scale, we examined its reliability and sensitivity. Thirteen children (aged 5 to 6 years) completed two identical incremental maximal running trials during a period of one week. A group of 12 adolescents and a group of 12 adults also tested the RPE-C by performing one trial under the same experimental conditions as the child group. RPE-C was recorded at the end of each load level. Statistical analysis revealed significant effects for velocity (F = 23.98, p < 0.0001) with non-significant effects for the trials. Intraclass correlation coefficient (ICC) revealed an acceptable reliability of RPE-C at low and high exercise intensities but also showed a low reliability at intermediate load levels (0.17 < ICC < 0.77). A significant correlation between RPE-C and heart rate (r2 = 0.61, p < 0.0001) was observed in children. However, the r2 level was lower than that observed for the adolescent or adult groups. This finding demonstrates the sensitivity of RPE-C to discriminate the effects of age on perceived exertion. RPE-C seems to be a good tool which can be used in young children to monitor exercise performed at low and high intensities.

Age Factors↗

PubMed2001

Does endurance or sprint training influence the perception of the optimal pedalling rate during submaximal cycling exercise?

The purpose of this study was to investigate the effects of endurance and sprint training on the perception of the optimal pedalling rate during a submaximal cycling exercise. Six subjects specialized in endurance activities and 6 subjects trained in sprinting activities used the model of bicycling at various pedalling rates with the same power output (150W) on a cycle ergometer. Individual 2nd order polynomial relationships were determined between oxygen consumption (VO(2)) and velocity and between rate of perceived exertion (RPE) and velocity. Optimal velocity, with respect to minimum of VO(2) (OV(VO2)) and to minimum of RPE (OV(RPE)), were calculated for all subjects, respectively. The close similarity found between the VO(2)-velocity and the RPE-velocity curves confirmed that the overall RPE was mainly influenced by the central factor. As OV(RPE) and OV(VO2) were not significantly correlated and as OV(RPE) was significantly higher than OV(VO2), other factors than central may also have influenced the RPE. The significant higher OV(RPE) values (p<0.05) observed in the sprint vs. endurance groups suggested that different training background may have influenced the RPE. These differences could also be explained by a significantly higher OV(VO2) in sprint than in endurance groups, the subjects being sensitive to the pedalling rate for which the energy expenditure is minimal.

Adult↗

PubMed2001

Specific and transfer effects induced by arm or leg training.

The purpose of the present study was to examine both the specific and the transfer effects of a Square Wave Endurance Exercise Test (SWEET) and to investigate the determining factors of transfer effect. A control group (CG, n = 5) and 2 experimental groups were studied. Experimental groups completed 3 days/week a 45 min SWEET over 6 weeks, either with the arms using a wheelchair ergometer (AG, n = 5) or with the legs using a cycling ergometer (LG, n = 5). All subjects performed before and after training two maximal progressive tests: the first one with the arms and the second with the legs. During those tests oxygen uptake (VO(2)) and cardiorespiratory parameters were continuously measured. Specific effects (changes between the tests performed with trained limbs) were observed: the peak power output (W(p)) and VO(2) were significantly increased by both arm (+ 66 %, + 35 %) and leg (+ 17 %, + 14 %) training. At ventilatory threshold (VT), power output (W) and VO(2) were significantly increased with arm (+ 145 % and + 51 %) and leg (+ 53 % and + 46 %) training. Transfer effects (changes between pre and post tests performed with untrained limbs) were observed: W(p) and VO(2) were not increased in AG while W(p) was increased in LG (+ 11 %). At VT, W and VO(2) were increased with arm (+ 19 % and + 23 %) and leg (+ 33 % and + 46 %) training. For AG and LG the VO(2) expressed in percent of the VO(2) peak was increased (+ 19 % and + 33 %, respectively) and the O(2p) was also increased (+ 30 %) for LG. These results show that SWEET training induced specific and transfer effects. Moreover, the initial level of the subjects, the type and the intensity of the training seem to be the major factors for effective observable transfer effects.

Adolescent↗

PubMed2001

Is the VO2 slow component dependent on progressive recruitment of fast-twitch fibers in trained runners?

The goal of this study was to use spectral analysis of EMG data to test the hypothesis that the O2 uptake VO2) slow component is due to a recruitment of fast fibers. Thirteen runners carried out a treadmill test with a constant speed, corresponding to 95% of the velocity associated with maximal VO2. The VO2 response was fit with the classical model including three exponential functions. Electrical activity of six lower limb muscles (vastus lateralis, soleus, and gastrocnemius of both sides) was measured using electromyogram surface electrodes. Mean power frequency (MPF) was used to study the kinetics of the electromyogram discharge frequency. Three main results were observed: 1) a common pattern of the MPF kinetics in the six muscles studied was noted; 2) MPF decreased in the first part of the exercise, followed by an increase for all the muscles studied, but only the vastus lateralis, and gastrocnemius muscles of both sides increased significantly (P < 0.05); and 3) the beginning of the MPF increase of the four muscles mentioned above corresponded with the beginning of the slow component. Our results suggest a progression in the average frequency of the motor unit discharge toward the high frequencies, which coheres with the hypothesis of the progressive recruitment of fast-twitch fibers during the VO2 slow component. However, this interpretation must be taken with caution because MPF is the result of a balance between several phenomena.

Adolescent↗

PubMed2001

Comparison of oxygen uptake kinetics during concentric and eccentric cycle exercise.

O2 uptake (VO2) kinetics and electromyographic (EMG) activity from the vastus medialis, rectus femoris, biceps femoris, and medial gastrocnemius muscles were studied during constant-load concentric and eccentric cycling. Six healthy men performed transitions from baseline to high-intensity eccentric (HE) exercise and to high-intensity (HC), moderate-intensity (MC), and low-intensity (LC) concentric exercise. For HE and HC exercise, absolute work rate was equivalent. For HE and LC exercise, VO2 was equivalent. VO2 data were fit by a two- or three-component exponential model. Surface EMG was recorded during the last 12 s of each minute of exercise to obtain integrated EMG and mean power frequency. Only in the HC exercise did VO2 increase progressively with evidence of a slow component (phase 3), and only in HC exercise was there evidence of a coincident increase with time in integrated EMG of the vastus medialis and rectus femoris muscles (P < 0.05) with no change in mean power frequency. The phase 2 time constant was slower in HC [24.0 +/- 1.7 (SE) s] than in HE (14.7 +/- 2.8 s) and LC (16.7 +/- 2.2 s) exercise, while it was not different from MC exercise (20.6 +/- 2.1 s). These results show that the rate of increase in VO2 at the onset of exercise was not different between HE and LC exercise, where the metabolic demand was similar, but both had significantly faster kinetics for VO2 than HC exercise. The VO2 slow component might be related to increased muscle activation, which is a function of metabolic demand and not absolute work rate.

Adult↗

PubMed1999

Optimal pedalling velocity characteristics during maximal and submaximal cycling in humans.

The aim of this study was to compare optimal pedalling velocities during maximal (OVM) and submaximal (OVSM) cycling in human, subjects with different training backgrounds. A group of 22 subjects [6 explosive (EX), 6 endurance (EN) and 10 non-specialised subjects] sprint cycled on a friction-loaded ergometer four maximal sprints lasting 6 s each followed by five 3-min periods of steady-state cycling at 150 W with pedalling frequencies varying from 40 to 120 rpm. The OVM and OVSM were defined as the velocities corresponding to the maximal power production and the lowest oxygen consumption, respectively. A significant linear relationship (r2 = 0.52, P < 0.001) was found between individual OVM [mean 123.1 (SD 11.2) rpm] and OVSM [mean 57.0 (SD 4.9) rpm, P < 0.001] values, suggesting that the same functional properties of leg extensor muscles influence both OVM and OVSM. Since EX was greater than EN in both OVM and OVSM (134.3 compared to 110.9 rpm and 60.8 compared to 54.0 rpm, P < 0.01 and P < 0.05, respectively) it could be hypothesised that the distribution of muscle fibre type plays an important role in optimising both maximal and submaximal cycling performance.

Adult↗

PubMed1999

Validation of simple tests of biathlon shooting ability.

The aim of this study was to validate three simple tests of biathlon shooting abilities. Twelve expert biathletes performed visual reaction time tests adapted for the rifle in the standing (RT-S) and prone positions (RT-P), and a tremometer test adapted for the rifle in the standing position (TT-S). Six consecutive days' measurements showed an acceptable reproducibility for these tests (coefficient of variation = 1.2% for RT-S, 1.1% for RT-P and 6.5% for TT-S). A significant difference was observed between TT-S at rest and after roller skiing 2.1 km at 90 % of maximal heart rate. This finding demonstrates the sensitivity of TT-S to discriminate the effects of fatigue on postural control. Among 24 biathletes of regional to expert level, significant correlations were observed between resting RT-P and prone shooting performance after roller skiing (r2 = 0.23; p = 0.01) and between resting TT-S and shooting performance in the standing position after roller skiing (r2 = 0.68; p = 0.0001), demonstrating the specificity of these tests. From these results, we conclude that TT-S is a valid field test of biathlon shooting performance.

Adult↗

PubMed1999

Simplified deceleration method for assessment of resistive forces in cycling.

PURPOSE: The purpose of this study was to develop and test a simplified deceleration technique for measurement of aerodynamic and rolling resistances in cycling. METHODS: Coast-down tests were performed in level hallways with an experienced cyclist as the rider. Average initial velocities were 2.5-12.8 m x s(-1)) The deceleration technique was simplified by the use on only three switches and a derivation that did not require an assumption that deceleration is constant. The effective frontal area (AC(D)) and coefficient of rolling resistance (CR) were then calculated through a derivation from the equation for resistive forces opposing motion. Method reproducibility was tested by comparison of results for four tests of 30 trials under identical conditions. Method sensitivity was tested by performing 30 trials with three different rider head positions and four different transported mass conditions. RESULTS: Analysis of variance revealed that there were no differences among the results in the reproducibility study for either AC(D) or C(R). Furthermore, the reproducibility tests revealed mean errors of only 0.66% and 0.70% for AC(D) and CR, respectively. ANOVA identified a significant increase (P < 0.001) in rolling resistance with external loading and a significant effect (P < 0.001) of head position on AC(D). Mean (+/-SD) values for AC(D) and C(R) from tests in a racing aeroposture with the head up, the head in line with the trunk, and the head in an intermediate position were 0.304 +/- 0.011, 0.268 +/- 0.010, and 0.262 +/- 0.013 m2, respectively. C(R) averaged 0.00368 in the three head positions. CONCLUSIONS: The findings indicate that this simplified deceleration technique is satisfactorily reproducible and sensitive for measurement of aerodynamic and rolling resistances in cycling.

Adult↗

PubMed1998

Energy cost and running mechanics during a treadmill run to voluntary exhaustion in humans.

The aim of the present study was to examine the physiological and mechanical factors which may be concerned in the increase in energy cost during running in a fatigued state. A group of 15 trained triathletes ran on a treadmill at velocities corresponding to their personal records over 3000m [mean 4.53 (SD 0.28) m x s(-1)] until they felt exhausted. The energy cost of running (CR) was quantified from the net O2 uptake and the elevation of blood lactate concentration. Gas exchange was measured over 1 min firstly during the 3rd-4th min and secondly during the last minute of the run. Blood samples were collected before and after the completion of the run. Mechanical changes of the centre of mass were quantified using a kinematic arm. A significant mean increase [6.9 (SD 3.5)%, P < 0.001] in CR from a mean of 4.4 (SD 0.4) J x kg(-1) x m(-1) to a mean of 4.7 (SD 0.4) J x kg(-1) x m(-1) was observed. The increase in the O2 demand of the respiratory muscles estimated from the increase in ventilation accounted for a considerable proportion [mean 25.2 (SD 10.4)%] of the increase in CR. A mean increase [17.0 (SD 26.0)%, P < 0.05] in the mechanical cost (CM) from a mean of 2.36 (SD 0.23) J x kg m(-1) to a mean of 2.74 (SD 0.55) J x kg(-1) x m(-1) was also noted. A significant correlation was found between CR and CM in the non-fatigued state (r=0.68, P < 0.01), but not in the fatigued state (r=0.25, NS). Furthermore, no correlations were found between the changes (from non-fatigued to fatigued state) in CR and the changes in CM suggesting that the increase in CR is not solely dependent on the external work done per unit of distance. Since step frequency decreased slightly in the fatigued state, the internal work would have tended to decrease slightly which would not be compatible with an increase in CR. A stepwise regressions showed that the changes in CR were linked (r=0.77, P < 0.01) to the changes in the variability of step frequency and in the variability of potential cost suggesting that a large proportion of the increase in CR was due to an increase in the step variability. The underlying mechanisms of the relationship between CR and step variability remains unclear.

Adult↗