Biomedical subjects

Christophe Hausswirth

Publications and source records attributed to Christophe Hausswirth.

9 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↗

PubMed2006

Muscle activation during cycling at different cadences: effect of maximal strength capacity.

The purpose of this study was to examine the influence of maximal strength capacity on muscle activation, during cycling, at three selected cadences: a low cadence (50 rpm), a high cadence (110 rpm) and the freely chosen cadence (FCC). Two groups of trained cyclists were selected on the basis of the different maximal isokinetic voluntary contraction values (MVCi) of their lower extremity muscles as follow: F(min) (lower MVCi group) and F(max) (higher MVCi group). All subjects performed three 4-min cycling exercises at a power output corresponding to 80% of the ventilatory threshold under the three cadences. Neuromuscular activity of vastus lateralis (VL), rectus femoris (RF) and biceps femoris (BF) was studied quantitatively (integrated electromyography, IEMG) and qualitatively (timing of muscle bursts during crank cycle). Cadence effects were observed on the EMG activity of VL muscle and on the burst onset of the BF, VL and RF muscles. A greater normalized EMG activity of VL muscle was observed for the F(min) group than the F(max) group at all cadences (respectively F(min) vs. F(max) at 50 rpm: 17+/-5% vs. 38+/-6%, FCC: 22+/-7% vs. 44+/-5% and 110 rpm: 21+/-6% vs. 45+/-6%). At FCC and 110 rpm, the burst onset of BF and RF muscles of the F(max) group started earlier in the crank cycle than the F(min) group These results indicate that in addition to the cadence, the maximal strength capacity influences the lower extremity muscular activity during cycling.

Adult↗

PubMed2006

Vitamin and mineral supplementation and neuromuscular recovery after a running race.

PURPOSE: This double-blind study investigated the effects of vitamin and mineral complex supplementation on the neuromuscular function of the knee-extensor muscles after a prolonged trail running race. METHODS: Twenty-two well-trained endurance runners took either placebo (Pl group) or vitamins and minerals (Vm group) for 21 d before the race and for 2 d after the race. Maximal voluntary contractions (MVC) and surface EMG activity of the vastus lateralis (VL) muscle were recorded before (pre) and 1 h (post), 24 h (post 24) and 48 h (post 48) after the race. Central activation ratio (CAR), neural (M-wave), and contractile (muscular twitch) properties of the quadriceps muscles were analyzed using electrical stimulation techniques. RESULTS: The knee-extensor MVC was significantly (P < 0.01) reduced after exercise for both groups (Vm: 36.5 +/- 3.0 %; Pl: 36.9 +/- 2.1%), but MVC recovery was greater for Vm than Pl after 48 h (11%, P < 0.05). The reduced MVC after exercise was associated with a significant reduction in maximal EMG normalized to the M-wave in VL muscle and in CAR for both groups. Characteristics of the muscular twitch were not significantly altered for either groups, whereas M-wave duration increased significantly (P < 0.05) after exercise. CONCLUSIONS: The reduction of MVC immediately after the race appeared to result from peripheral mechanisms such as a failure in muscle membrane excitation and, to a lesser extent, from reduced central activation. The cause of the depressed MVC 24 h after the race seemed to be located within the muscle itself. A dietary supplementation of a vitamin and mineral complex does not attenuate the loss of contractile function immediately after the running exercise, and it may accelerate the recovery of maximal force capacity.

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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

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.

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