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Biomedical subjects

J Brisswalter

Publications and source records attributed to J Brisswalter.

At least 19 recordsLinked to original sources
PubMed2006

Assessment of energy demand in Laser sailing: influences of exercise duration and performance level.

In this study we analyzed the influence of both exercise duration and skill level on energy demand in Laser sailing. Twenty-three subjects volunteered for this study. The population is divided into two groups according to their skill level: 13 high (HS) and 10 low (LS). Every subject performed a 30 min upwind sailing test, with a tacking every 2 min. Heart rate (HR), gas exchange and respiratory parameters were analyzed throughout the trial, and measured blood lactate concentration ([La(bl)] at rest and immediately after the exercise completion. Three, 4 min intervals were selected for analysis: 6-10 min (T10), 16-20 min (T20) and 26-30 min (T30). In contrast to previous studies, we found significantly progressive aerobic energy metabolism with sailing duration in the HS group (T10 = 45%; T20 = 61%; T30 = 68% VO2max, P < 0.05), whereas this demand remained stable, and significantly lower in LS group (T10 = 45%; T20 = 52%; T30 = 51% VO2max, P < 0.05). This study shows that aerobic demand is significantly more important in LS than in HS subjects after 30 min regatta, and could be an important factor in Laser regatta performance. We need further studies to confirm and explain this difference.

Adult↗
PubMed2006

Variable power output during cycling improves subsequent treadmill run time to exhaustion.

The aim of this study was to investigate the effect of constant versus variable power output cycling exercise on subsequent high-intensity, running performance. Eight triathletes completed two testing sessions (in a random order), which required the subjects to perform 30 min of cycling at either, a constant power output (90% of the lactate threshold), or a variable power output with power output alternating every 5 min (+/-20% of the constant workload). Each cycling bout was immediately followed by a high-intensity treadmill run (16.7+/-0.7 km h(-1)) to exhaustion. No significant differences were found for mean metabolic values or power output between cycling conditions. However, a significant (P<0.05) improvement in run time to exhaustion was reported after 30 min of variable cycling (15:09+/-4:43 min) compared to constant cycling (10:51+/-3:32 min). The results of this study demonstrate that, despite similar average physiological responses during 30 min of cycling, variable-intensity cycling results in an improved running performance compared to constant-intensity cycling. It is hypothesised that the reduced power output in the final 5 min of variable cycling protocol may allow recovery before transition, however the mechanisms involved cannot be determined from the current study.

Adult↗
PubMed2006

Is impairment similar between arm and leg cranking exercise in COPD patients?

UNLABELLED: Impaired skeletal muscle function has been reported in patients with chronic obstructive disease (COPD), but such impairment is not homogenous and its distribution between the upper and the lower limbs is still unclear. The present study was designed to assess and compare upper and lower limb capacities in patients with moderate to severe COPD during incremental and constant-load exercises. Thirteen COPD patients of similar age with moderate to severe air flow limitation (FEV(1): 35%+/-5% predicted) and 19 healthy subjects were studied. Four sessions were organized: two incremental and two constant-load cycling exercises with arm or leg in randomized order. As observed in a previous study involving incremental and constant tests, power, VO(2), RER, VE, and HR were all significantly lower in the upper and lower limbs of patients with COPD than in healthy controls. In the healthy population, aerobic capacity and mechanical efficiency (ME) were lower in the course of arm exercises than in leg exercises. For the same relative workload, dyspnea and blood lactate production were higher during arm exercise. In contrast, no significant difference was observed between arm and leg capacities for any of these parameters in COPD patients. CONCLUSION: Although aerobic capacity is impaired in COPD patients, arm aerobic capacity is relatively preserved. Given the lack of significant difference between arm and leg capacities in COPD, we hypothesize that upper limb muscles are less compromised than lower limb muscles in this patient population.

Aged↗
PubMed2005

Cadence selection affects metabolic responses during cycling and subsequent running time to fatigue.

OBJECTIVES: To investigate the effect of cadence selection during the final minutes of cycling on metabolic responses, stride pattern, and subsequent running time to fatigue. METHODS: Eight triathletes performed, in a laboratory setting, two incremental tests (running and cycling) to determine peak oxygen uptake (VO2PEAK) and the lactate threshold (LT), and three cycle-run combinations. During the cycle-run sessions, subjects completed a 30 minute cycling bout (90% of LT) at (a) the freely chosen cadence (FCC, 94 (5) rpm), (b) the FCC during the first 20 minutes and FCC-20% during the last 10 minutes (FCC-20%, 74 (3) rpm), or (c) the FCC during the first 20 minutes and FCC+20% during the last 10 minutes (FCC+20%, 109 (5) rpm). After each cycling bout, running time to fatigue (Tmax) was determined at 85% of maximal velocity. RESULTS: A significant increase in Tmax was found after FCC-20% (894 (199) seconds) compared with FCC and FCC+20% (651 (212) and 624 (214) seconds respectively). VO2, ventilation, heart rate, and blood lactate concentrations were significantly reduced after 30 minutes of cycling at FCC-20% compared with FCC+20%. A significant increase in VO2 was reported between the 3rd and 10th minute of all Tmax sessions, without any significant differences between sessions. Stride pattern and metabolic variables were not significantly different between Tmax sessions. CONCLUSIONS: The increase in Tmax after FCC-20% may be associated with the lower metabolic load during the final minutes of cycling compared with the other sessions. However, the lack of significant differences in metabolic responses and stride pattern between the run sessions suggests that other mechanisms, such as changes in muscular activity, probably contribute to the effects of cadence variation on Tmax

Adult↗
PubMed2005

Effect of fluid ingestion on neuromuscular function during prolonged cycling exercise.

OBJECTIVES: To investigate the effects of fluid ingestion on neuromuscular function during prolonged cycling exercise. METHODS: Eight well trained subjects exercised for 180 minutes in a moderate environment at a workload requiring approximately 60% maximal oxygen uptake. Two conditions, fluid (F) and no fluid (NF) ingestion, were investigated. RESULTS: During maximal voluntary isometric contraction (MVC), prolonged cycling exercise reduced (p<0.05) the maximal force generating capacity of quadriceps muscles (after three hours of cycling) and root mean square (RMS) values (after two hours of cycling) with no difference between the two conditions despite greater body weight loss (p<0.05) in NF. The mean power frequency (MPF) for vastus lateralis muscle was reduced (p<0.05) and the rate of force development (RFD) was increased (p<0.05) only during NF. During cycling exercise, integrated electromyographic activity and perceived exertion were increased in both conditions (p<0.05) with no significant effect of fluid ingestion. CONCLUSIONS: The results suggest that fluid ingestion did not prevent the previously reported decrease in maximal force with exercise duration, but seems to have a positive effect on some indicators of neuromuscular fatigue such as mean power frequency and rate of force development during maximal voluntary contraction. Further investigations are needed to assess the effect of change in hydration on neural mechanisms linked to the development of muscular fatigue during prolonged exercise.

Adult↗
PubMed2004

Effect of long duration exercise on the ratings of perceived exertion and perceived difficulty of walking and running at the ventilatory threshold.

AIM: The purpose of this study was to examine if the relationship between physiological changes classically observed with exercise duration and some subjective workload measures would be affected by the complexity of the locomotion mode (running vs racewalking). METHODS: The study was conducted on 24 well trained subjects (12 long distance runners and 12 racewalkers) divided in 3 groups (runners, racewalkers and control). Energy cost of locomotion (C), heart rate (HR), minute ventilation (V(E)), lactate concentration [La], ratings of perceived exertion (RPE 6-20 scale) and ratings of perceived difficulty (RPD 1(-1)5 scale) were recorded during 2 10-min submaximal tests on a treadmill before and immediately after a 3 hour exercise (racewalking or running) conducted at the velocity ventilatory threshold (vVT). RESULTS: No significant variations in physiological parameters and perceived measures were observed in G(c). A significant increase (p<0.05) in energy cost of walking (mean: +9.4%) and running (mean: +7.5%) at the end of exercise was observed. A significant interaction of locomotion mode and exercise duration was found on perceived exertion and perceived difficulty. In racewalkers RPD significantly increased with duration whereas no significant effect was found for RPE. Conversely a significant increase in RPE was found after 3 hours in runners without any significant change in RPD. CONCLUSIONS: This experiment suggests that, for a complex task, the classical relationship between RPE and metabolic load increase during prolonged exercise could be affected by changes in RPD. In this study, stability in RPE and increase in RPD observed in racewalkers may reflect an attentional focus dissociated from internal sensations and directed toward maintaining the required race walking gait.

Adult↗
PubMed2003

Effect of cycling cadence on subsequent 3 km running performance in well trained triathletes.

OBJECTIVES: To investigate the effect of three cycling cadences on a subsequent 3000 m track running performance in well trained triathletes. METHODS: Nine triathletes completed a maximal cycling test, three cycle-run succession sessions (20 minutes of cycling + a 3000 m run) in random order, and one isolated run (3000 m). During the cycling bout of the cycle-run sessions, subjects had to maintain for 20 minutes one of the three cycling cadences corresponding to 60, 80, and 100 rpm. The metabolic intensity during these cycling bouts corresponded approximately to the cycling competition intensity of our subjects during a sprint triathlon (> 80% VO(2)max). RESULTS: A significant effect of the prior cycling exercise was found on middle distance running performance without any cadence effect (625.7 (40.1), 630.0 (44.8), 637.7 (57.9), and 583.0 (28.3) seconds for the 60 rpm run, 80 rpm run, 100 rpm run, and isolated run respectively). However, during the first 500 m of the run, stride rate and running velocity were significantly higher after cycling at 80 or 100 rpm than at 60 rpm (p<0.05). Furthermore, the choice of 60 rpm was associated with a higher fraction of VO(2)max sustained during running compared with the other conditions (p<0.05). CONCLUSIONS: The results confirm the alteration in running performance completed after the cycling event compared with the isolated run. However, no significant effect of the cadence was observed within the range usually used by triathletes.

Bicycling↗
PubMed2001

Effect of pedalling rates on physiological response during endurance cycling.

This study was undertaken to examine the effect of different pedalling cadences upon various physiological responses during endurance cycling exercise. Eight well-trained triathletes cycled three times for 30 min each at an intensity corresponding to 80% of their maximal aerobic power output. The first test was performed at a freely chosen cadence (FCC); two others at FCC - 20% and FCC + 20%, which corresponded approximately to the range of cadences habitually used by road racing cyclists. The mean (SD) FCC, FCC - 20% and FCC + 20% were equal to 86 (4), 69 (3) and 103 (5) rpm respectively. Heart rate (HR), oxygen uptake (VO2), minute ventilation (VE) and respiratory exchange ratio (R) were analysed during three periods: between the 4th and 5th, 14th and 15th, and 29th and 30th min. A significant effect of time (P < 0.01) was found at the three cadences for HR, VO2. The VE and R were significantly (P < 0.05) greater at FCC + 20% compared to FCC - 20% at the 5th and 15th min but not at the 30th min. Nevertheless, no significant effect of cadence was observed in HR and VO2. These results suggest that, during high intensity exercise such as that encountered during a time-trial race, well-trained triathletes can easily adapt to the changes in cadence allowed by the classical gear ratios used in practice.

Adult↗
PubMed2001

Single and choice reaction time during prolonged exercise in trained subjects: influence of carbohydrate availability.

The aim of the present study was to examine the effects of prolonged exercise at the ventilatory threshold and carbohydrate ingestion on single (SRT) and choice (CRT) reaction time. Eight well-trained triathletes completed three testing sessions within a 3-week period. Maximal oxygen uptake was determined in the first test, whereas the second and the third sessions were composed of a 100-min run (treadmill 15 min, overground 70 min, treadmill 15 min) performed at the velocity associated with the ventilatory threshold. During these submaximal tests, the subjects ingested (in random order) 8 ml x kg(-1) body weight of either a placebo (Pl) or 5.5% carbohydrate (CHO) solution prior to the first submaximal run and 2 ml x kg(-1) body weight every 15 min after that. The cognitive tasks were performed before and after exercise for CRT, and before, during each submaximal run and after exercise for SRT. Furthermore, at the end of each submaximal test subjects were asked to report their rating of perceived exertion (RPE). Results showed a significant positive effect of CHO ingestion on RPE and CRT performance at the end of exercise, while no effect of exercise duration was found in the Pl condition. After a 100-min run, during the CHO condition, CRT mean (SD) group values decreased from 688.5 (51) ms to 654 (63) ms, while during the Pl condition, RPE mean group values increased from 11 (2) to 16 (1.02) and CRT mean values remained stable [688 (104) ms vs 676 (73.4) ms, P > 0.05]. No similar effect was observed for SRT. These results suggest that CHO-electrolyte ingestion during a 100-min run results in an improvement in the complex cognitive performance measured at the end of that run.

Adult↗
PubMed2001

Effect of two drafting modalities in cycling on running performance.

PURPOSE: The purposes of this study were first to compare the physiological responses during a triathlon where cycling was performed alternatively with another cyclist (alternate draft triathlon, ADT) or continuously behind him (continuous draft triathlon, CDT), and second to study the incidence of these two drafting modalities in cycling on the subsequent running performance done during a simulated triathlon. METHODS: Ten male triathletes of national level performed a sprint distance triathlon (0.75-km swim, 20-km bike, 5-km run) on two different sessions, one where the triathlete alternatively rode in front or at the back of another cyclist and rotating every 500 m, the other where the triathlete drafted continuously a professional cyclist whose task was to reproduce all split times recorded during the alternate situation. Oxygen uptake (VO2), expiratory flow (VE), heart rate (HR) were recorded during the entire bike and run sections and blood lactate concentrations ([La-]b) were analyzed at the end of each event composing the triathlon. RESULTS: The results showed that expiratory flow, oxygen uptake, heart rate and blood lactate concentrations were significantly lower in CDT on the bike compared with drafting in alternation (148.1 vs. 167.2 L.min-1, 49.9 vs. 59.8 mL.min-1.kg-1, 154.7 vs. 173.1 beats.min-1, 3.5 vs. 6.3 mmol.L-1, respectively). The results also revealed that running after biking in CDT (for similar cycling speeds) significantly improved the subsequent running speed compared to ADT (17.87 vs. 17.15 km.h-1). Furthermore, VE, VO2, HR, and [La-]b were significantly higher during CDT run compared with ADT run (175.6 vs. 170.4 L.min-1, 69.7 vs. 66.8 mL.min-1.kg-1, 182.6 vs. 177.3 beats.min-1, 9.6 vs. 7.5 mmol.L-1, respectively). CONCLUSIONS: These results showed that drafting continuously behind a lead cyclist allows triathletes to save a significant amount of energy during the bike leg of a sprint triathlon and creates the conditions for an improved running performance compared with a situation where cycling is performed alternating the lead with another cyclist.

Adult↗
PubMed2001

Effects of a prolonged run on simple reaction time of well trained runners.

The aim of the present study was to examine the effect of increased arousal induced by a prolonged exercise at ventilatory threshold simple reaction time performance performed during a running task. 11 well trained triathletes completed two testing sessions within a 2-wk. period. The first session was a protocol of VO2 max determination conducted on a treadmill. This protocol was used to assess the velocity associated with ventilatory threshold (vVvt). The second session was a 90-min. running test performed at vVvt. This last session was composed of five submaximal treadmill runs (10-min. long, 0% grade) separated by four overground runs (10-min.). Before, during each treadmill run, and after exercise, subjects performed three blocks of 20 simple reaction time. Furthermore, at the end of each overground run, perceived exertion (RPE) was recorded. Analysis showed a significant impairment in Simple RT performance during the first treadmill run only. After this first run a significant effect of exercise duration on Simple RT was observed. After 40-min. of exercise a significant improvement in reaction time during exercise was recorded, Furthermore, when Simple RT was recorded at rest, there was no difference pre-exercise and postexercise. These results suggest that a simple cognitive performance could be improved during exercise, despite the negative effect of the dual task. This improvement in reaction time could be explained mainly by an increase in arousal induced by a prolonged exercise.

Adult↗
PubMed2001

Effect of exercise duration on optimal pedaling rate choice in triathletes.

The purpose of this study was to investigate the effect of an exercise duration similar to triathlon's cyclism event (approximately 1 hr), on factors determining the freely chosen cadence. Nine trained triathletes completed a cycling track session conducted at a speed corresponding to 75% of maximal heart rate. This session was composed of five submaximal rides performed at five cadences presented in a random order (65, 80, 95, 110 rpm and freely chosen cadence) realized before and after a 1-hr exercise at the freely chosen cadence. Results show, during the first condition, that triathletes choose spontaneously a cadence (90,1 +/- 10,7 rpm) close to the neuromuscular optimum (89,6 +/- 1,1 rpm) while at the end of exercise, a decrease of the freely chosen cadence (82,8 +/- 8,7 rpm) was observed toward the energetically optimal cadence (78,6 +/- 5,8 rpm). These findings suggest the hypothesis of an adaptation of the movement pattern with the exercise duration in order to minimize the energy cost rather than the neuromuscular cost of cycling.

Adult↗
PubMed2000

Carbohydrate ingestion does not influence the change in energy cost during a 2-h run in well-trained triathletes.

The aim of this study was to examine whether the increase in the energy cost of running (C(r)), previously reported to occur at the end of a prolonged run, could be influenced by the ingestion of either an artificially sweetened placebo (Pl) or a 5.5% carbohydrate (CHO) solution. Ten well-trained triathletes completed three testing sessions within a 3-week period. The aim of the first session was to determine maximal oxygen uptake (VO(2)(max)) and the velocity associated with ventilatory threshold (nu(VT)). The second and the third sessions were composed of two submaximal treadmill runs (20 min long, 0% grade, performed at nu(VT)), before and after an 80-min overground run, also conducted at nu(VT). During these submaximal tests, the subjects ingested (in a random order) either a Pl or CHO solution prior to the first submaximal run and every 20 min after that. During the first session, ventilatory threshold (VT) occurred at [mean (SD)] 81.2 (2.5)% VO(2)(max) and 16.5 (0.6) km. h(-1). A significant effect of exercise duration was found on C(r) (DeltaC(r)) at the end of the run, whatever the solution ingested (DeltaC(r) = 5.7% and 7.01% for CHO and Pl, respectively). A reduction in the respiratory exchange ratio (from 0.98 to 0.90) was observed only at the end of the Pl trial. In this study, C(r) seems to be affected only to a minor extent by substrate turnover. Moreover, the increase in the demand for oxygen, estimated from the increase in ventilation, accounted for only a minor proportion of the increase in C(r) (11% and 17% for CHO and Pl, respectively). No correlation was found between the changes in C(r) and the changes in the other physiological parameters recorded. These results suggest, indirectly, that C(r) increases during a 2-h run at 80% VO(2)(max) in well-trained subjects can be explained mainly by alterations in neuromuscular performance, which lead to a decrease in muscle efficiency.

Administration, Oral↗
PubMed2000

Evolution of electromyographic signal, running economy, and perceived exertion during different prolonged exercises.

The purpose of this study was to compare the electromyographic (EMG) signal of the vastus lateralis muscle obtained during a run section of a triathlon and at the end of a prolonged run performed at the same running velocity. Seven subjects were studied on three occasions: a 2 h 15 min triathlon (30 min swimming, 60 min cycling, and 45 min treadmill running at 75% of the maximal aerobic speed), a 2 h 15 min run, where the last 45 min (Prolonged Run, PR) were run at the same speed as the Triathlon Run (TR) on a motorized treadmill, and a 45 min Isolated Run (IR) performed at the same TR and PR velocity. The three experimental trials were randomised. Oxygen uptake (VO2), heart rate (HR), and EMG data were recorded during the three run sections. The results confirm a greater VO2 and HR during PR compared with IR (P<0.01) and TR (P<0.05). Also the VO2 values obtained during TR were significantly greater compared to IR (P < 0.05). EMG signal, obtained from the vastus lateralis muscle during 4 sec of isometric contraction at 35 % of maximal voluntary contraction (MVC), showed that after PR the mean power frequency (MPF) shifted significantly to lower frequencies (P<0.01) compared with MPF recorded before the prolonged run. Moreover, the signal amplitude (RMS) was increased significantly after PR in comparison to pre-trial (P < 0.01). Similar results were obtained for the TR at P < 0.05. The integrated EMG flow, QIEMG (iEMG/burst duration), recorded during all run sections, was significantly increased near the end of PR (i.e. 2 h 10 min of running) compared with QiEMG recorded after 1 h 30 min of running. No significant increase in QiEMG was observed with TR and IR situations. The results suggest that a long exercise bout of running led to a greater increase in muscle fatigue compared with a triathlon or an isolated run performed at the same running speed. In addition it is suggested that the rating of perceived exertion recorded during isometric contractions is a good indice to approach the level of fatigue during prolonged exercises.

Adult↗
PubMed2000

Energetically optimal cadence vs. freely-chosen cadence during cycling: effect of exercise duration.

The purpose of this study was to examine the relationship between cadence and oxygen consumption with exercise duration. Ten triathletes who trained regularly were examined. The first test was always a maximal test to determine maximal oxygen uptake (VO2max). The other sessions were composed of six submaximal tests representing 80% of the maximal power reached with VO2max (Pmax). During these tests submaximal rides with a duration of 30 min were performed. Each test represented, in a randomised order, one of the following pedal rates: 50, 65, 80, 95, 110 rpm and a freely-chosen rate. VO2, respiratory parameters, and heart rate were monitored continuously. Two periods, between the 3rd and the 6th minute and between the 25th and the 28th minute, were analysed. Results showed that when VO2 and heart rate were plotted against cadence, each curve could be best described by a parabolic function, whatever the period. Furthermore, a significant effect of period was found on energetically optimal cadence (70 +/- 4.5 vs. 86 +/- 6.2 rpm, P < 0.05). Only during the second period was no significant difference found between freely-chosen cadence (83 +/- 6.9 rpm) and energetically optimal cadence (P > 0.05). In conclusion, our results suggest that during prolonged exercise triathletes choose a cadence that is close to the energetically optimal cadence. A change of muscle fibre recruitment pattern with exercise duration and cadence would explain the shift in energetically optimal rate towards a higher pedal rate observed at the end of exercise.

Adult↗
PubMed2000

Evidence of neuromuscular fatigue after prolonged cycling exercise.

PURPOSE: The purpose of this study was to analyze the effects of prolonged cycling exercise on metabolic, neuromuscular, and biomechanical parameters. METHODS: Eight well-trained male cyclists or triathletes performed a 2-h cycling exercise at a power output corresponding to 65% of their maximal aerobic power. Maximal concentric (CON; 60, 120, 240 degrees x s(-1)), isometric (ISO; 0 degrees s(-1)), and eccentric (ECC; -120, -60 degrees x s(-1)) contractions, electromyographic (EMG) activity of vastus lateralis (VL) and vastus medialis (VM) muscles were recorded before and after the exercise. Neural (M-wave) and contractile (isometric muscular twitch) parameters of quadriceps muscle were also analyzed using electrical stimulation techniques. RESULTS: Oxygen uptake (VO2), minute ventilation (VE), and heart rate (HR) significantly increased (P < 0.01) during the 2-h by, respectively, 9.6%, 17.7%, and 12.7%, whereas pedaling rate significantly decreased (P < 0.01) by 21% (from 87 to 69 rpm). Reductions in muscular peak torque were quite similar during CON, ISO, and ECC contractions, ranging from 11 to 15%. M-wave duration significantly increased (P < 0.05) postexercise in both VL and VM, whereas maximal amplitude and total area decreased (VM: P < 0.05, VL: NS). Significant decreases in maximal twitch tension (P < 0.01), total area of mechanical response (P < 0.01), and maximal rate of twitch tension development (P < 0.05) were found postexercise. CONCLUSIONS: A reduction in leg muscular capacity after prolonged cycling exercise resulted from both reduced neural input to the muscles and a failure of peripheral contractile mechanisms. Several hypothesis are proposed to explain a decrease in pedaling rate during the 2-h cycling with a constancy of power output and an increase in energy cost.

Adult↗