Jacques Bouckaert

Mouth rinse but not ingestion of a carbohydrate solution improves 1-h cycle time trial performance.

The aim of the present study was to further explore the influence of ingestion and mouth rinse with a carbohydrate‐electrolyte solution (CES) on the performance during a ∼1 h high‐intensity time trial on trained subjects. Subjects rinsed around the mouth or ingested a 6% isotonic CES or placebo (14 mL/kg body weight) before and throughout a time trial in which they had to accomplish a set amount of work (975±85 kJ) as quickly as possible. In the mouth rinse conditions, time to complete the test was shorter (P=0.02) with CES (61.7±5.1 min) than with placebo (64.1±6.5 min), whereas in the ingestion conditions, there was no difference between placebo (62.5±6.9 min) and CES (63.2±6.9 min). Although power output and lactate concentration during exercise were significantly higher when subjects rinsed their mouth with CES compared with placebo, the rating of perceived exertion values did not differ. Blood glucose concentration increased after ingestion of but not after mouth rinse with CES. The interesting finding of the present study is that rinsing the mouth with but not ingestion of CES resulted in improved performance.

The influence of exercise and dehydration on postural stability

The aim of this study was to investigate the effects of exercise-induced and thermal dehydration on postural balance. Eight male subjects cycled for 2 h at a power output equal to 57-63% VO2max on two different occasions: once without drinking (NF) and once with intake of 1.9 l of a carbohydrate-electrolyte solution (FR). Before and after the exercise test, the velocity of the centre of pressure (COP) excursion was measured on a force platform during 30-s bipedal standing in normal position, feet side by side, and tandem position, feet heel to toe. On another occasion, eight subjects underwent seven consecutive sauna sessions (85 degrees C, 50% rh) of 15 min duration with no fluid replacement (S) to induce thermal dehydration. Mean fluid loss was 2.7 (+/- 0.4)%, 0.5 (+/- 0.5)% and 3.0 (+/- 0.6)% of body mass after NF, FR and S, respectively. Mean velocity of COP excursion after the exercise test was significantly higher in the NF than in the FR trial (p < 0.05). Postural stability was not influenced by S. In conclusion, prolonged exercise without fluid ingestion seems to negatively affect postural stability, whereas no effect is observed after exercise with fluid replacement or after thermal dehydration.

Oxygen uptake kinetics during high-intensity arm and leg exercise

The purpose of the present study was to examine the oxygen uptake kinetics during heavy arm exercise using appropriate modelling techniques, and to compare the responses to those observed during heavy leg exercise at the same relative intensity. We hypothesised that any differences in the response might be related to differences in muscle fibre composition that are known to exist between the upper and lower body musculature. To test this, ten subjects completed several bouts of constant-load cycling and arm cranking exercise at 90% of the mode specific V(O(2)) peak. There was no difference in plasma [lactate] at the end of arm and leg exercise. The time constant of the fast component response was significantly longer in arm exercise compared to leg exercise (mean+/-S.D., 48+/-12 vs. 21+/-5 sec; P < 0.01), while the fast component gain was significantly greater in arm exercise (12.1+/-1.0 vs. 9.2+/-0.5 ml min(-1) W(-1); P < 0.01). The V(O(2)) slow component emerged later in arm exercise (126+/-27 vs. 95+/-20 sec; P < 0.01) and, in relative terms, increased more per unit time (5.5 vs. 4.4% min(-1); P < 0.01). These differences between arm crank and leg cycle exercise are consistent with a greater and/or earlier recruitment of type II muscle fibres during arm crank exercise.

The effects of a pedometer-based behavioral modification program with telephone support on physical activity and sedentary behavior in type 2 diabetes patients

OBJECTIVE Effectiveness of a behavioral modification program on physical activity (PA) and sedentary behavior in diabetes patients. METHODS Ninety-two patients were randomly assigned to an intervention or control group. The 24-weeks intervention consisted of a face-to-face session, pedometer and seven telephone follow-ups. Mean selection criteria were 35-75 years; 25-35 kg/m(2); ≤ 12% HbA1c, treated for type 2 diabetes; no PA limitations. PA and sedentary behavior were measured by pedometer, accelerometer and questionnaire over the short- (24 weeks) and intermediate- (1 year) term. RESULTS The intervention group increased their steps/day by 2744, their total PA by 23 min/day (p<0.001) and decreased their sedentary behavior by 23 min/day (p<0.05) post-intervention. After 1 year the intervention group still had an increase of 1872 steps/day, 11 min/day total PA and a decrease of 12 min/day in sedentary behavior (p<0.001). CONCLUSION This pedometer-based behavioral modification program with telephone support showed lasting positive effects on steps/day, PA and sedentary behavior. PRACTICE IMPLICATIONS This study tested a convenient way to increase PA among type 2 diabetes patients.

In humans the oxygen uptake slow component is reduced by prior exercise of high as well as low intensity

Abstract The aim of the study was to examine to what extent prior high- or low-intensity cycling, yielding the same amount of external work, influenced the oxygen uptake (V˙O2) slow component of subsequent high-intensity cycling. The 12 subjects cycled in two protocols consisting of an initial 3 min period of unloaded cycling followed by two periods of constant-load exercise separated by 3 min of rest and 3 min of unloaded cycling. In protocol 1 both periods of exercise consisted of 6 min cycling at a work rate corresponding to 90% peak oxygen uptake (V˙O2peak). Protocol 2 differed from protocol 1 in that the first period of exercise consisted of a mean of 12.1 (SD 0.8) min cycling at a work rate corresponding to 50% V˙O2peak. The difference between the 3rd min V˙O2 and the end V˙O2 (ΔV˙O2(6−3)) was used as an index of the V˙O2 slow component. Prior high-intensity exercise significantly reduced ΔV˙O2(6−3). The ΔV˙O2(6−3) was also reduced by prior low-intensity exercise despite an unchanged plasma lactate concentration at the start of the second period of exercise. The reduction was more pronounced after prior high- than after prior low-intensity exercise (59% and 28%, respectively). The results of this study show that prior exercise of high as well as low intensity reduces the V˙O2 slow component and indicate that a metabolic acidosis is not a necessary condition to elicit a reduction in ΔV˙O2(6−3).

Effects of distraction on treadmill running time in severely obese children and adolescents

OBJECTIVE: (1) To examine the effects of attentional distraction on running time in an incremental treadmill test in obese youngsters; (2) to investigate whether distraction works at the same extent at the beginning and at the end of residential treatment; and (3) to explore the underlying mechanisms of the possible distraction effects.METHODS: Thirty severely obese youngsters (10 boys, 20 girls, age range 9–17) who were following a 10 month residential treatment, performed a treadmill test until exhaustion in four different sessions using a within subjects design. The two sessions at the beginning of the treatment and the two sessions at the end the treatment were counterbalanced, one with attentional distraction (music) and one without distraction.RESULTS: Obese youngsters ran significantly longer during distraction. This distraction effect seemed to be larger at the beginning compared to at the end of obesity treatment. The absence of differences between the condition with music and the condition without music on perceived bodily symptoms is in line with the idea that it took longer to perceive sufficient bodily sensations to decide to stop the treadmill test in the distraction condition. This interpretation is further corroborated by the physiological data indicating a superior peak performance in the condition with distraction.CONCLUSIONS: Attentional distraction has a positive effect on perseverance in obese youngsters. Further research has to show the usefulness of attentional distraction as a technique to increase exercise adoption and adherence in obesity treatment.

Effect of Exercise Protocol on Deoxy[Hb + Mb]: Incremental Step versus Ramp Exercise

PURPOSE The aim of the present study was to investigate whether the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise is specific to non-steady-state conditions. METHODS Ten highly trained cyclists performed an incremental step (40 W x 3 min(-1)) and ramp (35 W x min(-1)) exercise. Deoxy[Hb + Mb] was measured at the distal and proximal sites of the musculus vastus lateralis throughout the exercises using near-infrared spectroscopy. Deoxy[Hb + Mb] was set out as a function of work rate (% peak power), and using curve-fitting techniques, the best-fitting model was determined. RESULTS These procedures showed that the sigmoid pattern also provided the best fit for the pattern of deoxy[Hb + Mb] in the step exercise. Furthermore, it was observed that the sigmoid model was similar for the ramp (d = 6.9% +/- 1.1% and 6.9% +/- 1.4% x %(-1) peak power; c/d = 52.1% +/- 3.8% and 52.1% +/- 4.5% peak power, for the proximal and distal measurement sites, respectively) and the step exercise (d = 7.4% +/- 1.5% and 6.4% +/- 1.5% x %(-1) peak power; c/d = 52.3% +/- 6.0% and 52.5% +/- 4.2% peak power, for the proximal and distal measurement sites, respectively). The pattern of deoxy[Hb + Mb] was not influenced by measurement site. CONCLUSIONS From the present study, it can be concluded that the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise is not specific to non-steady-state conditions. It was hypothesized that this pattern is an expression of a nonlinear Q x m/V x O2m relationship, related to changes in muscle fiber-type recruitment.

The VO2 response to submaximal ramp cycle exercise: Influence of ramp slope and training status.

The aim of the study was to test whether ramp slope and training status interact in the oxygen uptake (VO2) response during submaximal ramp exercise. Eight cyclists (VO2 peak=67.8+/-3.7 ml min(-1)kg(-1)) and eight physically active students (PA students) (VO2 peak=49.1+/-4.3 ml min(-1)kg(-1)) performed several ramp protocols, respectively, 25 and 40 W min(-1) for the cyclists and 10, 25 and 40 W min(-1) for the PA students. Vo(2) was plotted as a function of time and work rate up to the gas exchange threshold (GET). Faster ramp elicited a significantly shorter mean response time (MRT) in both groups, and MRT was significantly longer for each ramp protocol in the PA students (126+/-32s, 76+/-15s and 50+/-6s for ramp 10, ramp 25 and ramp 40, respectively) compared to the cyclists (61+/-9s and 40+/-11s for ramp 25 and ramp 40, respectively). Ramp 40 showed less steep Delta VO2/Delta W than ramp 25 in both groups (p<0.01) and Delta VO2/Delta W was less steep for each ramp protocol in PA students (p<0.01) (9.82+/-0.30 ml min(-1)W(-1) and 9.33+/-0.45 ml min(-1)W(-1) for ramp 25 and ramp 40, respectively) compared to cyclists (10.31+/-0.40 ml min(-1)W(-1) and 10.05+/-0.48 ml min(-1)W(-1) for ramp 25 and ramp 40, respectively). In the PA students, Delta VO2/Delta W did not differ between ramp 10 and ramp 25. Statistical analysis showed no interaction effects between ramp slope and training status for MRT (p=0.62) and Delta VO2/Delta W (p=0.35).

Effects of training on maximal working capacity and haemodynamic response during arm and leg-exercise in a group of paddlers

Maximal oxygen uptake and circulatory adaptation to work with legs and arms were studied in a group of 5 paddlers members of the Belgian national squad and a control-group of 9 trained subjects. The results showed that the specific armtraining of paddlers induced changes in the arm-to-leg ratio of physiological parameters at submaximal and maximal work. In the group of paddlers maximal oxygen intake and workload during arm-exercise averaged respectively 88.6% and 80.3% of the scores obtained with leg-exercise. In the control group the arm to leg ratio varied between 81.2% and 65.2%. At a submaximal load of 100 W the difference in heartfrequency was 21 beats/min in the canoë group and 35 beats/min in the control group. Oxygen consumption and ventilation during work with the arms was lower in the group of paddlers. The data of our study suggest that the specific training of paddlers do result in a effect on the haemodynamic adaptations to arm work

Dietary arginine supplementation speeds pulmonary VO2 kinetics during cycle exercise.

PURPOSE To test the hypothesis that L-arginine (the substrate for nitric oxide synthase [NOS]) administration slows the VO2 kinetics at the onset of moderate-intensity exercise in humans. METHODS Seven physically active males were randomly assigned to receive either placebo (lactose) or L-arginine hydrochloride capsules (7.2 g x d(-1)) for 14 d in a double-blind crossover design, with a 7-d washout period between the two conditions. On day 11 and day 14 of each condition, the subjects completed two consecutive 6-min bouts of cycle exercise at 80% of the ventilatory threshold with a 12-min rest interval. VO2 was measured on a breath-by-breath basis, and VO2 kinetics were determined with a single exponential model from the averaged data derived from four repetitions. Capillary and venous blood samples were taken to determine plasma [La] and serum [arginine], respectively. RESULTS There were no differences in circulating lactate either before or during exercise. However, serum [arginine] was higher (P < 0.05) in the arginine condition at rest (119.0 +/- 12.6 vs 103.6 +/- 15.7 micromol x L(-1) in the control condition) and after exercise (113.3 +/- 26.0 vs 103.8 +/- 12.6 micromol x L(-1) in the control condition). With regard to the pulmonary VO2 kinetics, no significant difference was observed in the time at which the phase II response emerged or in the phase II amplitude between the two conditions. However, contrary to our hypothesis, the time constant was significantly reduced after arginine administration (i.e., 13.9 +/- 3.1 vs 15.8 +/- 2.6 s in the control condition, P < or = 0.014). CONCLUSION Exogenous L-arginine administration speeds the phase II pulmonary VO2 response by 12% at the onset of moderate-intensity exercise in humans.