The relationship between changes in steps/day and health outcomes after a pedometer-based physical activity intervention with telephone support in type 2 diabetes patients.

The study aim was to investigate the health effects of a pedometer-based behavioural modification program in type 2 diabetes patients and to examine the relationship between changes in steps/day (baseline-post and baseline-follow up) and health outcomes. Ninety-two type 2 diabetes patients (69% male, mean age: 62 ± 9 years and mean BMI: 30.0 ± 2.5 kg/m(2)) were recruited and randomly assigned to an intervention or control group. The intervention consisted of one face-to-face session, pedometer use and seven telephone calls. Selection criteria included 35-75 years, 25-35 kg/m(2) and ≤12% HbA1c (108 mmol/mol). Outcome measures were assessed at baseline, post and follow up, and included systolic blood pressure, waist circumference, body mass index, glucose control (HbA1c and fasting glucose), triglycerides, total, HDL and LDL cholesterol and steps/day. The results showed no significant short- or intermediate-term differences in health outcomes between the control and intervention group. However, a threshold was identified, as HbA1c improved significantly in those who increased ≥4000 steps/day between baseline- and post-measurements (n = 18). This threshold was not applicable to any other health outcome. Hence, although the intervention successfully increased steps/day, no direct effect on health outcomes was identified. However, an increase of ≥4000 steps/day seemed a threshold to have a positive impact on HbA1c.

Influence of priming exercise on muscle deoxy[Hb + Mb] during ramp cycle exercise.

The aim of the present study was to gain better insight into the mechanisms underpinning the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise by assessing the changes in the profile following prior high-intensity exercise. Ten physically active students performed two incremental ramp (25 W min(-1)) exercises (AL and LL, respectively) preceded on one occasion by incremental arm (10 W min(-1)) and on another occasion by incremental leg exercise (25 W min(-1)), which served as the reference test (RT). Deoxy[Hb + Mb] was measured by means of near-infrared spectroscopy and surface EMG was recorded at the Vastus Lateralis throughout the exercises. Deoxy[Hb + Mb], integrated EMG and Median Power Frequency (MdPF) were expressed as a function of work rate (W) and compared between the exercises. During RT and AL deoxy[Hb + Mb] followed a sigmoid increase as a function of work rate. However, during LL deoxy[Hb + Mb] increased immediately from the onset of the ramp exercise and thus no longer followed a sigmoid pattern. This different pattern in deoxy[Hb + Mb] was accompanied by a steeper slope of the iEMG/W-relationship below the GET (LL: 0.89 ± 0.11% W(-1); RT: 0.74 ± 0.08% W(-1); AL: 0.72 ± 0.10% W(-1)) and a more pronounced decrease in MdPF in LL (17.2 ± 4.5%) compared to RT (5.0 ± 2.1%) and AL (3.9 ± 3.2%). It was observed that the sigmoid pattern of deoxy[Hb + Mb] was disturbed when the ramp exercise was preceded by priming leg exercise. Since the differences in deoxy[Hb + Mb] were accompanied by differences in EMG it can be suggested that muscle fibre recruitment is an important underlying mechanism for the pattern of deoxy[Hb + Mb] during ramp 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.

Aerobic fitness, muscle efficiency, and motor unit recruitment during ramp exercise.

PURPOSE: The purpose of this study was to test whether the higher slope of the oxygen uptake/work rate relationship (DeltaVO2/DeltaW) in aerobically trained subjects compared with less trained counterparts during a ramp protocol is related to changes in muscle fiber activation. METHODS: Ten cyclists and 10 physically active (PA) students performed two ramp exercises (ramp 25 protocol and relative ramp protocol, leading to exhaustion in 12 min) and a step protocol (20-60-100-140-180-220 W). Pulmonary gas exchange was measured, and muscle fiber activity was recorded with surface EMG of the musculus vastus lateralis. V O2 and integrated EMG (iEMG) were described as functions of work rate up to the gas exchange threshold, and linear regression analysis was used to determine the DeltaVO2/DeltaW and the slope of the iEMG/W relationship (DeltaiEMG/DeltaW). RESULTS: The statistical analysis revealed a higher DeltaVO2/DeltaW in cyclists compared with PA students in ramp exercises (ramp 25 = 9.98 +/- 0.51 vs 9.18 +/- 0.59 mL x min(-1) x W(-1); relative ramp = 9.87 +/- 0.30 vs 9.16 +/- 0.33 mL x min(-1) x W(-1) in the cyclists and PA students, respectively; P < 0.05) but not in step exercise (9.97 +/- 0.32 and 9.83 +/- 0.37 mL x min(-1) x W(-1) in cyclists and PA students, respectively; P > 0.05). In addition, cyclists demonstrated a higher DeltaiEMG/DeltaW in ramp exercises (0.96 +/- 0.14% x W(-1) and 0.98 +/- 0.14% x W(-1) in ramp 25 and relative ramp, respectively) compared with step exercise (0.75 +/- 0.12% x W(-1), P < 0.05), whereas in the PA students, DeltaiEMG/DeltaW did not differ between the ramp protocol (0.75 +/- 0.10% x W(-1) and 0.70 +/- 0.12% x W(-1) in ramp 25 and relative ramp, respectively) and the step protocol (0.77 +/- 0.17% x W(-1), P > 0.05). CONCLUSIONS: The present study reveals that trained cyclists demonstrate reduced mechanical efficiency in the ramp protocol and that this phenomenon is associated with an "overactivation" of muscle fibers.

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.

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.

Pattern of deoxy[Hb+Mb] during ramp cycle exercise: influence of aerobic fitness status.

During ramp exercise the deoxy[Hb + Mb] pattern follows a sigmoid model [f(x) = f (0) + A/(1 + exp(-(-c +dx))], indicating a non-linear muscle blood flow (Qm)/oxygen uptake (VO25)-relationship. We hypothesised that in trained cyclists the sigmoid would display a rightward shift, due to an increased oxidative capacity and/or higher percentage of slow-twitch fibres. A total of 10 cyclists and 11 physically active students (PA students) performed a relative ramp exercise (+/-12 min) and a ramp25-exercise (25 W min(-1)). Deoxy[Hb + Mb] was measured at the M. Vastus Lateralis by NIRS, normalized to the total amplitude of the response and expressed as a function of absolute and relative (%peakP) work rate. The work rate corresponding to c/d (i.e.50% of the amplitude of the deoxy[Hb + Mb] response) was the only parameter of the sigmoid that differed significantly between cyclists (57.9 +/- 4.4% and 60.1 +/- 4.1%peakP in the relative and ramp25, respectively) and PAstudents (49.6 +/- 4.2% and 48.2 +/- 5.1%peakP, respectively), indicating a rightward shift of the sigmoid in the cyclists. These results suggest a change in the time course of C((a-v))O(2) as a function of aerobic fitness status.

Balance and postural skills in normal-weight and overweight prepubertal boys.

OBJECTIVE: This study investigated differences in balance and postural skills in normal-weight versus overweight prepubertal boys. METHODS: Fifty-seven 8-10-year-old boys were categorized overweight (N = 25) or normal-weight (N = 32) according to the International Obesity Task Force cut-off points for overweight in children. The Balance Master, a computerized pressure plate system, was used to objectively measure six balance skills: sit-to-stand, walk, step up/over, tandem walk (walking on a line), unilateral stance and limits of stability. In addition, three standardized field tests were employed: standing on one leg on a balance beam, walking heel-to-toe along the beam and the multiple sit-to-stand test. RESULTS: Overweight boys showed poorer performances on several items assessed on the Balance Master. Overweight boys had slower weight transfer (p < 0.05), lower rising index (p < 0.05) and greater sway velocity (p < 0.001) in the sit-to-stand test, greater step width while walking (p < 0.05) and lower speed when walking on a line (p < 0.01) compared with normal-weight counterparts. Performance on the step up/over test, the unilateral stance and the limits of stability were comparable between both groups. On the balance beam, overweight boys could not hold their balance on one leg as long (p < 0.001) and had fewer correct steps in the heel-to-toe test (p < 0.001) than normal-weight boys. Finally, overweight boys were slower in standing up and sitting down five times in the multiple sit-to-stand task (p < 0.01). CONCLUSION: This study demonstrates that when categorised by body mass index (BMI) level, overweight prepubertal boys displayed lower capacity on several static and dynamic balance and postural skills.

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).

Predictors of 6-minute walk test and 12-minute walk/run test in obese children and adolescents.

UNLABELLED: The purpose of this study was to identify predictors of the distance achieved during a 6-minute walk test and a 12-minute walk/run test (Cooper test) in obese children and adolescents and to evaluate the influence of a residential treatment on the association of these predictors with the distance. A search of the Revalidation Centre Zeepreventorium (De Haan, Belgium) medical records database of all children and adolescents (age 10 to 18 yrs) treated for obesity between September 2003 and February 2006, revealed 65 charts with all relevant data (anthropometrical, maximal graded exercise, lung function, 6-minute walk test and 12-minute walk/run test) at admission as well as after 3 months treatment. The multidisciplinary treatment has a positive influence on anthropometrical variables, endurance capacity, vital capacity, and residual volume (p < 0.05). The distance covered during the 6-minute walk test and the 12-minute walk/run test is correlated with all anthropometrical data and peak VO2 (p < 0.05). After 3 months of treatment, bivariate correlation was stronger for almost every parameter compared to admission. Following a stepwise regression, BMI z-score is a dominant predictor of both field tests at admission and after 3 months treatment. VO2peak contributes only significantly in the 12-minute walk/run test at admission. CONCLUSION: In obese children and adolescents BMI z-score is the most dominant predictor of the variability in performances on the 6-minute walk test and the 12-minute walk/run test at admission as well as after 3 months of treatment.

Role of physical activity and eating behaviour in weight control after treatment in severely obese children and adolescents.

AIM: To investigate the role of physical activity and eating behaviour in weight control 1.5 y after a weight-reduction programme in severely obese children. METHODS: Forty-seven children (13.4 +/- 2.1 y) were measured 1.5 y after the completion of a 10-mo residential treatment programme. Stature and body mass were measured; physical activity, fat and fibre intake, and self-efficacy in relation to physical activity and healthy eating behaviour were assessed using validated structured interviews. The total sample was divided into four subgroups according to unhealthy versus healthy physical activity and eating behaviour at follow-up. RESULTS: One-and-a-half years after treatment, subjects had regained 34 +/- 19% overweight, but were on average still 20 +/- 19% less overweight than before treatment (p < 0.001). The four subgroups did not differ in level of overweight at the beginning or end of treatment. At follow-up, there was a significant difference in overweight between the four subgroups (p < 0.05). The least healthy group (unhealthy physical activity and unhealthy eating behaviour) had a significantly higher level of overweight 1.5 y after treatment (183 +/- 36%) in comparison with the other groups (unhealthy physical activity and healthy eating: 150 +/- 21%; healthy physical activity and unhealthy eating: 156 +/- 14%; healthy physical activity and healthy eating: 138 +/- 16%) (p < 0.05), whilst the healthiest group showed the lowest level of overweight after treatment when compared to the other groups (p < 0.05). CONCLUSION: Results suggest that both physical activity and nutritional habits play an important role in weight maintenance after initial weight loss in obese children and that one healthy behaviour can not compensate for another unhealthy behaviour.

Prior arm exercise speeds the VO2 kinetics during arm exercise above the heart level.

PURPOSE: To test the hypothesis that the initial O2 uptake kinetics during exercise where the rise in blood flow (and, by implication, O2 delivery) to the working muscles during an abrupt increase in exercise intensity is reduced (i.e., arm exercise performed above the level of the heart) would be faster when preceded by a bout of high-intensity exercise. METHODS: Eleven physically active males completed two protocols, each consisting of two consecutive bouts of 6 min of high-intensity arm crank exercise separated by 6 min of recovery. In one protocol, the arm crank exercise was performed with the arms below the level of the heart (HL). RESULTS: In the HL protocol, the amplitudes of the VO2 fast and slow component were unaffected by prior exercise, whereas the VO2 fast component time constant was significantly reduced in the second bout (49.8+/-22.1 vs 40.7+/-13.2 s; P<0.05). CONCLUSION: The results of this study demonstrate that prior high-intensity exercise caused a significant speeding of the VO2 fast component response during subsequent high-intensity arm crank exercise performed above, and not below, the level of the heart.

Influence of DCA on pulmonary (.-)V(O2) kinetics during moderate-intensity cycle exercise.

PURPOSE: To test the hypothesis that pharmacological activation of the pyruvate dehydrogenase enzyme complex (PDC) with dichloroacetate (DCA) would speed phase II pulmonary oxygen uptake ((.-)V(O2)) kinetics after the onset of subsequent moderate-intensity (40-45% ((.-)V(O2)) peak) cycle exercise. METHODS: Seven healthy males (mean +/- SD age 25 +/- 4 yr, body mass 75.3 +/- 9.4 kg) performed four "square-wave" transitions from unloaded cycling to a work rate requiring 90% of the predetermined gas exchange threshold either with or without prior infusion of DCA (50 mg x kg body mass in 50 mL saline). Pulmonary ((.-)V(O2)) was measured breath-by-breath in all tests and ((.-)V(O2)) kinetics were determined from the averaged individual response to each condition using nonlinear regression techniques. RESULTS: The blood [lactate] measured immediately before the onset of exercise was significantly reduced in the DCA condition (C: 1.1 +/- 0.3 vs DCA: 0.6 +/- 0.3 mM; P < 0.01) consistent with successful activation of the PDC. However, DCA had no discernible effect on the rate at which ((.-)V(O2)) increased toward the steady state after the onset of exercise as reflected in the phase II time constant (C: 28.5 +/- 11.8 vs DCA: 29.4 +/- 14.9 s). CONCLUSIONS: The results suggest that PDC activation does not represent a principal intramuscular limitation to ((.-)V(O2)) kinetics after the onset of moderate-intensity exercise.

Effects of training status and exercise intensity on phase II VO2 kinetics.

PURPOSE: To test the hypotheses that: 1) the time constant for the fast component of .VO2 kinetics (tau1) at exercise onset would be faster in trained than in untrained subjects for both moderate and heavy exercise, and that 2) tau1 would become progressively slower in untrained subjects at higher power outputs but be invariant in trained subjects. METHODS: Eight untrained subjects (.VO2peak: 42.9 +/- 5.1 mL.kg-1.min-1) and seven trained cyclists (.VO2peak: 66.6 +/- 2.5 mL.kg-1.min-1) completed square-wave transitions to power outputs requiring 60% and 80% of gas exchange threshold (GET), and 50% of the difference between GET and .VO2 peak (50%Delta) from a baseline of "unloaded" cycling. .VO2 was measured breath-by-breath and individual responses were modeled using nonlinear regression techniques. RESULTS: A repeated measures ANOVA revealed that the tau1 was significantly smaller (i.e., the kinetics were faster) in the trained compared with the untrained subjects and that tau1 became significantly greater (i.e., the kinetics were slowed) at higher power outputs both in the untrained (60%GET: 17.8 +/- 3.8 s, 80%GET: 21.5 +/- 6.6 s, and 50%Delta: 23.5 +/- 2.8 s) and the trained (60%GET: 8.9 +/- 1.3 s, 80%GET: 11.7 +/- 2.5 s, and 50%Delta: 15.2 +/- 2.0 s) subjects (P < 0.05). CONCLUSION: Phase II .VO2 kinetics became progressively slower at higher power outputs in both trained and untrained subjects. That a greater tau1 was evident at a higher power output within the moderate exercise intensity domain (

Changes in fat mass, fat-free mass and aerobic fitness in severely obese children and adolescents following a residential treatment programme.

UNLABELLED: The purpose of this study was to describe changes in fat mass (FM), fat-free mass (FFM) and aerobic fitness in severely obese children and adolescents during residential treatment in the Medical Paediatric Centre Zeepreventorium. Treatment consisted of moderate dietary restriction, physical activity and psychological support. This study was a clinical observation of 20 severely obese children and adolescents (8 boys and 12 girls, aged 15.4+/-1.8 years) who completed the 10-month residential programme. Height, weight, FM, FFM and aerobic fitness was measured four times during the intervention: at baseline, 11 weeks, 24 weeks and at 33 weeks (at the end of the programme ). The mean decrease in level of overweight was 46% (P<0.001), with a mean loss of 8.9% FM (P<0.001). Submaximal performance (PWC150) improved from 123+/-35 Watt to 152+/-37 Watt (P<0.001). Maximal performance levels increased (performance time: from 14+/-2.9 min to 15.3+/-3.5 min, peak power: from 186+/-38 Watt to 205+/-45 Watt, P<0.01) without an improvement in absolute VO(2 peak). CONCLUSION: A moderate dietary restriction in combination with physical activity and psychological support in severely obese children and adolescents is effective in decreasing body fat and improving physical performance. Further research is needed to evaluate the longer-term effects of such a programme.

Physical fitness and physical activity in obese and nonobese Flemish youth.

OBJECTIVE: To assess different aspects of physical fitness and physical activity in obese and nonobese Flemish youth. RESEARCH METHODS AND PROCEDURES: A random sample of 3214 Flemish schoolchildren was selected and divided into an "obese" and "nonobese" group based on body mass index and sum of skinfolds. Physical fitness was assessed by the European physical fitness test battery. Physical activity was estimated by a modified version of the Baecke Questionnaire. RESULTS: Obese subjects had inferior performances on all tests requiring propulsion or lifting of the body mass (standing-broad jump, sit-ups, bent-arm hang, speed shuttle run, and endurance shuttle run) compared with their nonobese counterparts (p < 0.001). In contrast, the obese subjects showed greater strength on handgrip (p < 0.001). Both groups had similar levels of leisure-time physical activity; however, nonobese boys had a higher sport index than their obese counterparts (p < 0.05). DISCUSSION: Results of this study show that obese subjects had poorer performances on weight-bearing tasks, but did not have lower scores on all fitness components. To encourage adherence to physical activity in obese youth, it is important that activities are tailored to their capabilities. Results suggest that weight-bearing activities should be limited at the start of an intervention with obese participants and alternative activities that rely more on static strength used.

Effect of prior heavy arm and leg exercise on VO2 kinetics during heavy leg exercise.

The aim of the present study was to examine the effect of prior exercise at a remote site on the VO(2) kinetics during subsequent heavy cycle exercise using a model that allowed us to discriminate between the VO(2) fast and slow component responses. Ten male subjects completed a constant-load exercise of 6 min cycling at 90% of the VO(2)peak in three conditions: without prior exercise (LE-C), after heavy cycling exercise (6 min at 90% of the VO(2)peak) (LE-L) and after heavy arm-cranking exercise (6 min at 90% of the arm VO(2)peak) (LE-A). Subjects performed four repetitions of each exercise protocol, separated by at least 1 day. VO(2) was measured on a breath-by-breath basis and VO(2) kinetics were determined with a biexponential model. There were no significant differences in the VO(2) fast component parameters between LE-C, LE-L and LE-A. However, the VO(2) slow component amplitude was significantly reduced in LE-L and LE-A compared to LE-C, but the reduction was less pronounced in LE-A [the value of the VO(2) slow exponential term at the end of exercise, A(2)', was 657 (SD 200) ml x min(-1) in LE-C versus 384 (SD 136) ml x min(-1) in LE-L and 551 (SD 169) m x min(-1) in LE-A; P<0.05]. The results of this study demonstrate that prior heavy arm exercise alters VO(2) kinetics during cycling exercise by reducing the VO(2)slow component amplitude, though this reduction is smaller than the reduction observed following prior heavy leg exercise. These data indicate that the primary factor causing changes in the VO(2) kinetics is probably located in the involved muscle.

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.

Effect of prior exercise on VO(2) slow component is not related to muscle temperature.

INTRODUCTION: It has been widely reported that the VO(2) slow component is reduced in the second of two bouts of heavy exercise. It has also been shown that an increase in muscle temperature (Tm) produced by wearing hot-water-perfused pants causes a reduction in the VO(2) slow component. Therefore, the aim of this study was to investigate whether the effect of prior heavy exercise on the VO(2) slow component of subsequent heavy exercise is related to the warming-up of the exercising limbs. METHODS: Six male subjects completed an exercise protocol consisting of two constant-load exercise bouts (EX-1 and EX-2) at 90% VO(2peak), separated by 6 min of rest. The Tm of the m. vastus lateralis was measured with an indwelling thermistor. Seven days later, the subjects completed a second exercise protocol consisting of a passive warming-up of the upper legs until the same Tm was reached as after EX-1, followed by a constant-load work bout (EX-3) identical to EX-1 and EX-2. RESULTS: Tm reached comparable levels at the start of EX-2 and EX-3 (37.3 +/- 0.6 degrees C and 37.2 +/- 0.3 degrees C, respectively). The VO(2) slow component (measured as deltaVO(2)(6-2 min)) was reduced by 57% after prior heavy exercise ( < 0.05), whereas no significant reduction was observed after prior passive warming-up. CONCLUSIONS: The results of this study indicate that the reduction in VO(2) slow component observed after prior heavy exercise cannot be explained by an increase in muscle temperature of the upper legs.