PubMed Health⌕ Search

Biomedical subjects

Laurent Messonnier

Publications and source records attributed to Laurent Messonnier.

6 recordsLinked to original sources
PubMed2005

Are the effects of training on fat metabolism involved in the improvement of performance during high-intensity exercise?

The objective of the present study was to relate changes in certain muscle characteristics and indicators of metabolism in response to endurance training to the concomitant changes in time to exhaustion (T(lim)) at a work rate corresponding to maximal oxygen uptake VO(2speak). Eight healthy sedentary subjects pedalled on a cycle ergometer 2 h a day, 6 days a week, for 4 weeks. Training caused increases in VO(2peak) (by 8%), T(lim) (from 299 +/- 23 s before to 486 +/- 63 s after training), citrate synthase and 3-hydroxyl-acyl-CoA dehydrogenase (HAD) activities (by 54% and 16%, respectively) and capillary density (by 31%). Decreases in activity of lactate dehydrogenase (LDH) and muscle type of LDH (by 24% and 28%, respectively) and the phosphofructokinase/citrate synthase ratio (by 37%) were also observed. Respiratory exchange ratio (RER) tended to be lower (P < 0.1) at all relative work rates after training while the corresponding ventilation rates (VE) were unchanged. At the same absolute work rate, RER and (VE) were lower after training (P < 0.05). The improvement of T(lim) with training was related to the increases in HAD activity (r = 0.91, P = 0.0043), and to the decreases in RER calculated for Pa(peak) (r = 0.71, P = 0.0496). The present results suggest that the training-induced adaptations in fat metabolism might influence T(lim) at a work rate corresponding to VO(2peak) and stimulate the still debated and incompletely understood role of fat metabolism during short high-intensity exercise.

Acyl-CoA Dehydrogenase↗
PubMed2004

Effects of training in normoxia and normobaric hypoxia on time to exhaustion at the maximum rate of oxygen uptake.

The effects of endurance training in normoxia or in hypoxia on time to exhaustion ( T(lim)) at the work rate corresponding to peak oxygen uptake (VO(2peak)) were examined at sea level in 13 healthy subjects. Before and after training the subjects performed the following: (1) incremental exercises up to exhaustion to determine peak oxygen uptake in normoxia (VO(2peak)N), the percentage of this value at the 4 mmol l(-1) blood lactate concentration (VO(2)4%N) and the work rate corresponding to VO(2peak)N (Pa(peak)N), (2) a 5-min 90% Pa(peak)N exercise followed by a 10-min passive recovery to determine the maximal blood lactate concentration (La(max)) measured during the recovery, and (3) a T(lim) at Pa(peak)N. Training consisted of pedalling 2 h a day, 6 days a week, for 4 weeks. Five subjects trained in normobaric hypoxia [HT; partial pressure of inhaled oxygen ( P(I)O(2)) 89 mmHg] and eight subjects trained at the same relative work rates in normoxia (NT; P(I)O(2) 141 mmHg). The training-induced improvement of all the measured parameters were closely matched between the HT and the NT ( P>0.05). Training increased T(lim) by 59.7% [164(40) s]. The value of T(lim) was related to VO(2)4%N and to La(max) before and after training. Also, the training-induced improvement of T(lim) was related to the concomitant decrease in La(max). It is concluded that: (1) endurance training including continuous high-intensity exercises improves T(lim) for exercises performed at the same relative (higher absolute) work rate after training, (2) intermittent hypoxic training has no potentiating effect on T(lim) as compared with training in normoxia, and (3) the intra-individual training-induced improvement of T(lim) was associated with metabolic alteration in relation to lactate accumulation.

Adult↗
PubMed2003

Cardioventilatory changes induced by mentally imaged rowing.

Mentally imaged but unexecuted physical activity has been reported to induce a cardiorespiratory change. In order to test whether the previous experience of the performed exercise was a prerequisite to observe these changes, ventilation and heart rate were recorded during mental imagination of a rowing race in four groups of volunteers: 12 competitive rowers, 10 non-rower athletes, 12 students (22-30 years old) and 12 senior subjects (50-60 years old). Recordings were performed at rest, during the viewing of a rowing race and during mental imagination of this race. Analysis of variance revealed significant condition effect for all cardiorespiratory variables. All subjects increased their breathing rate (mean increase: 16 breaths.min(-1) in rowers, 8 breaths.min(-1) in athletes, 8 breaths.min(-1) in students, and 6 breaths.min(-1) in seniors), 29 decreased their tidal volume (mean decrease: 100 ml in rowers, 102 ml in athletes, 120 ml in students and 26 ml in seniors), with an increase in the resulting ventilation in 38 subjects (mean increase: 14 l.min(-1) in rowers, 3.6 l.min(-1) in athletes, 2.8 l.min(-1) in students, 2.6 l.min(-1) in seniors). Heart rate was increased in 34 subjects (mean increase: 12 beats.min(-1) in rowers, 5 beats.min(-1) in athletes, 6 beats.min(-1) in students and 5 beats.min(-1) in seniors). The number of subjects who exhibited changes was evenly distributed among the four groups. However, mean values of the changes were higher in rowers than in the three other groups, mainly due to three rowers who exhibited extremely large increases in cardioventilatory variables. Analysis of variance showed no significant group effect for heart rate and breathing rate. These results suggest that rowing experience may not be necessary for changes in heart rate and ventilation to be elicited by mentally imagining a rowing race.

Adaptation, Physiological↗
PubMed2003

Skiing across the Greenland icecap: divergent effects on limb muscle adaptations and substrate oxidation.

This study investigates the adaptive response of the lower limb muscles and substrate oxidation during submaximal arm or leg exercise after a crossing of the Greenland icecap on cross-country skies. Before and after the 42-day expedition, four male subjects performed cycle ergometer and arm-cranking exercise on two separate days. On each occasion, the subjects exercised at two submaximal loads (arm exercise, 45 W and 100 W; leg exercise, 100 W and 200 W). In addition, peak oxygen uptake ((VO(2max))) was determined for both leg and arm exercise. Before and after the crossing, a muscle biopsy was obtained from the vastus lateralis and the triceps brachii muscles prior to exercise (N=3). After the crossing, body mass decreased by 5.7+/-0.5 kg (in four of four subjects), whereas (VO(2max)) was unchanged in the arm (3.1+/-0.2 l min(-1)) and leg (4.0+/-0.1 l min(-1)). Before the crossing, respiratory exchange ratio (RER) values were 0.84+/-0.02 and 0.96+/-0.02 during submaximal arm exercise and 0.82+/-0.02 and 0.91+/-0.01 during submaximal leg exercise at the low and high workloads, respectively. After the crossing, RER was lower (in three of four subjects) during arm exercise (0.74+/-0.02 and 0.81+/-0.01) but was higher (in three of four subjects) during leg exercise (0.92+/-0.02 and 0.96+/-0.01) at the low and high workloads, respectively. Citrate synthase and beta-hydroxy-acyl-CoA-dehydrogenase activity was decreased by approximately 29% in vastus lateralis muscle and was unchanged in triceps brachii muscle. Fat oxidation during submaximal arm exercise was enhanced without a concomitant increase in the oxidative capacity of the triceps brachii muscle after the crossing. This contrasted with decreased fat oxidation during leg exercise, which occurred parallel to a decreased oxidative capacity in vastus lateralis muscle. Although the number of subjects is limited, these results imply that the adaptation pattern after long-term, prolonged, low-intensity, whole body exercise may vary dramatically among muscles.

Adaptation, Physiological↗