Biomedical subjects

Thierry Bernard

Publications and source records attributed to Thierry Bernard.

8 recordsLinked to original sources

PubMed2006

Constant versus variable-intensity during cycling: effects on subsequent running performance.

The aim of this study was to investigate the metabolic responses to variable versus constant-intensity (CI) during 20-km cycling on subsequent 5-km running performance. Ten triathletes, not only completed one incremental cycling test to determine maximal oxygen uptake and maximal aerobic power (MAP), but also three various cycle-run (C-R) combinations conducted in outdoor conditions. During the C-R sessions, subjects performed first a 20-km cycle-time trial with a freely chosen intensity (FCI, approximately 80% MAP) followed by a 5-km run performance. Subsequently, triathletes were required to perform in a random order, two C-R sessions including either a CI, corresponding to the mean power of FCI ride, or a variable-intensity (VI) during cycling with power changes ranging from 68 to 92% MAP, followed immediately by a 5-km run. Metabolic responses and performances were measured during the C-R sessions. Running performance was significantly improved after CI ride (1118 +/- 72 s) compared to those after FCI ride (1134 +/- 64 s) or VI ride (1168 +/- 73 s) despite similar metabolic responses and performances reported during the three cycling bouts. Moreover, metabolic variables were not significantly different between the run sessions in our triathletes. Given the lack of significant differences in metabolic responses between the C-R sessions, the improvement in running time after FCI and CI rides compared to VI ride suggests that other mechanisms, such as changes in neuromuscular activity of peripheral skeletal muscle or muscle fatigue, probably contribute to the influence of power output variation on subsequent running performance.

Adult↗

PubMed2005

Modification of cycling biomechanics during a swim-to-cycle trial.

The aim of this study was to investigate the effects of drafting, i.e., swimming directly behind a competitor, on biomechanical adaptation during subsequent cycling. Eight well-trained male triathletes underwent three submaximal sessions in a counterbalanced order. These sessions comprised a 10-min ride on a bicycle ergometer at 75% of maximal aerobic power (MAP) at a freely chosen cadence. This exercise was preceded either by a 750-m swim performed alone at competition pace (SCA trial; swimming-cycling alone), a 750-m swim in a drafting position at the same pace as during SCA (SCD trial; swimming-cycling with drafting), or a cycling warm-up at 30% of MAP for the same duration as the SCA trial (CTRL trial). The results indicated that the decrease in metabolic load when swimming in a drafting position (SCD trial) was associated with a significantly lower pedal rate and significantly higher mean and peak resultant torques when compared to the SCA trial, p < 0.05. These results could be partly explained by the lower relative intensity during swimming in the SCD trial when compared with the SCA trial, involving a delayed manifestation of fatigue in the muscles of the lower limbs at the onset of cycling.

Adult↗

PubMed2005

Does prior 1500-m swimming affect cycling energy expenditure in well-trained triathletes?

The purpose of this study was to determine the effects of a 1,500-m swim on energy expenditure during a subsequent cycle task. Eight well-trained male triathletes (age 26.0 +/- 5.0 yrs; height 179.6 +/- 4.5 cm; mass 71.3 +/- 5.8 kg; VO(2)max 71.9 +/- 7.8 ml.kg(-1).min(-1)) underwent two testing sessions in counterbalanced order. The sessions consisted of a 30-min ride on the cycle ergometer at 75% of maximal aerobic power (MAP), and at a pedaling frequency of 95 rev.min(-1), preceded either by a 1,500-m swim at 1.20 m.s(-1) (SC trial) or by a cycling warm-up at 30% of MAP (C trial). Respiratory and metabolic data were collected between the 3rd and the 5th min, and between the 28th and 30th min of cycling. The main results indicated a significantly lower gross efficiency (13.0%) and significantly higher blood lactate concentration (56.4%), VO(2) (5.0%), HR (9.3%), VE (15.7%), and RF (19.9%) in the SC compared to the C trial after 5 min, p < 0.05. After 30 min, only VE (7.9%) and blood lactate concentration (43.9%) were significantly higher in the SC compared to the C trial, p < 0.05. These results confirm the increase in energy cost previously observed during sprint-distance triathlons and point to the importance of the relative intensity of swimming on energy demand during subsequent cycling.

Adult↗

PubMed2003

[Effects of swimming with a wet suit on energy expenditure during subsequent cycling].

The aim of this study was to investigate the effects of swimming with a wetsuit on energy expenditure during subsequent cycling. Nine well-trained triathletes underwent three submaximal trials. The first trial (SC) consisted of a 750-m swim realised at a competition pace, followed by a 10-min cycling exercise at a power output corresponding to the ventilatory threshold . The two other trials were composed of the same cycling exercise, preceded either by a 750-m swim with a wetsuit (WSC) or by a cycling warm-up (Ctrl). The main results are that the WSC trial was characterised by significantly lower swimming cadence (-14%), heart rate (-11%), and lactate values (-47%) compared to the SC trial, p < 0.05. Moreover, cycling efficiency was significantly higher in the WSC trial compared to the SC trial (12.1% difference, p < 0.05). The lower relative intensity observed during swimming with a wetsuit suggest the relative importance of swimming condition on the total performance in a sprint triathlon.

Adult↗

PubMed2003

[Energy cost of running during a specific transition in duathlon].

The aim of the present study was to investigate the variability of the energy cost of running (Cr) during a simulated duathlon performed in outdoor conditions by elite duathletes. This duathlon consisted of 5 km of running, 30 km of cycling, and 5 km of running. The main result was the lack of significant difference in Cr between the two running bouts (210 +/- 10 mL d'O2.km-1.kg-1 vs. 217 +/- 10 mL d'O2.km-1.kg-1). This result is different from those observed during a triathlon, where an increase of energy cost of running bout has been reported. Furthermore, during a short-distance duathlon performed by well-trained subjects, none of the physiological (ventilation alteration, metabolic changes, or dehydration) or biomechanical factors that are classically evoked in triathlon research to explain Cr variability seem to be affected by the run-cycle-run transition. These results seem to minimize the negative effect of the cycle-to-run transition during a short-duration event in well-trained subjects.

Adult↗

PubMed2003

Habitual physical activity in children and adolescents during school and free days.

PURPOSE: The purpose of this study was to analyze habitual physical activity (HPA) of boys and girls from primary school to high school. METHODS: One hundred eighty-two schoolchildren and teenagers (6-20 yr) were studied at primary school (PS, N= 64), junior high school (JHS, N= 67), and senior high school (SHS, N= 51). HR was continuously monitored during the whole week to assess HPA during school days and free days. Total physical activity (TPA), low physical activity (LPA), moderate physical activity (MPA), and vigorous physical activity (VPA) were evaluated from the time spent each day above 50%HR reserve (HRR), below 50%HRR, between 50% and 70%HRR, and above 70%HRR, respectively. RESULTS: During school days, TPA decreased by 69% in male subjects (P< 0.05) and by 36% in female subjects (N= 0.058) from PS to SHS. In contrast, TPA did not vary significantly during free days (male subjects, PS: 62 +/- 37 min x d, SHS: 63 +/- 67 min x d; female subjects, PS: 75 +/- 59 min x d, SHS: 62 +/- 44 min x d ). Gender differences were only observed during school days at PS for TPA (male subjects: 121 +/- 37 min x d vs female subjects: 92 +/- 44 min x d, P< 0.05) and VPA (male subjects: 38 +/- 21 min x d vs female subjects: 18 +/- 12 min x d, P< 0.05). Male and female subjects were more inactive during free days than during school days at PS (P< 0.05). No effect of the type of day and gender was observed for all indices of HPA at high schools. CONCLUSIONS: Our results highlight the importance of taking into account the type of day (school day vs free day) in the analysis of children and adolescents' HPA.

Adolescent↗

PubMed2003

Drafting during swimming improves efficiency during subsequent cycling.

PURPOSE: The aim of the present study was to investigate the effects of drafting (i.e., swimming directly behind a competitor) while swimming with a wet suit on physiological parameters and cadence during subsequent cycling. METHODS: Eight well-trained male triathletes underwent two submaximal sessions conducted in a counterbalanced order. One of these sessions (SAC) consisted of a 750-m swim, performed at competition pace, followed by a 15-min ride on a bicycle ergometer at 75% of maximal aerobic power and at a freely chosen cadence. During the other session (SDC) the subjects swam 750 m in a drafting position at the same pace as during SAC and then performed the 15-min cycling test at the same intensity as during SAC. RESULTS: The main result indicated that cycling efficiency was significantly improved when the cycling session was preceded by a swimming bout performed in drafting position compared with an isolated swimming bout (+4.8%, P < 0.05). CONCLUSION: These results could be partly explained by the lower relative intensity observed during swimming in the SDC trial when compared with the SAC trial. This study suggests the relative importance of swimming condition and highlights the advantage of drafting during the swimming portion of a sprint triathlon.

Adult↗

PubMed2002

Influence of cycling cadence on subsequent running performance in triathletes.

PURPOSE: The purpose of this study was to investigate the influence of different cycling cadences on metabolic and kinematic parameters during subsequent running. METHODS: Eight triathletes performed two incremental tests (running and cycling) to determine maximal oxygen uptake (VO2max) and ventilatory threshold (VT) values, a cycling test to assess the energetically optimal cadence (EOC), three cycle-run succession sessions (C-R, 30-min cycle + 15-min run), and one 45-min isolated run (IR). EOC, C-R, and IR sessions were realized at an intensity corresponding to VT + 5%. During the cycling bouts of C-R sessions, subjects had to maintain one of the three pedaling cadences corresponding to the EOC (72.5 +/- 4.6 rpm), the freely chosen cadence (FCC; 81.2 +/- 7.2 rpm), and the theoretical mechanical optimal cadence (MOC, 90 rpm; Neptune and Hull, 1999). RESULTS: Oxygen uptake (VO2) increased during the 30-min cycling only at MOC (+12.0%) and FCC (+10.4%). During the running periods of C-R sessions, VO2, minute ventilation, and stride-rate values were significantly higher than during the IR session (respectively, +11.7%, +15.7%, and +7.2%). Furthermore, a significant effect of cycling cadence was found on VO2 variability during the 15-min subsequent run only for MOC (+4.1%) and FCC (+3.6%). CONCLUSION: The highest cycling cadences (MOC, FCC) contribute to an increase in energy cost during cycling and the appearance of a VO2 slow component during subsequent running, whereas cycling at EOC leads to a stability in energy cost of locomotion with exercise duration. Several hypotheses are proposed to explain these results such as changes in fiber recruitment or hemodynamic modifications during prolonged exercise.

Adult↗