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Carbohydrate stores within muscle are considered essential as a fuel for prolonged endurance exercise, and regimes for enhancing such stores have proved successful in aiding performance. This study explored the effects of a hyperglycaemic-hyperinsulinemic clamp performed 18 h previously on subsequent prolonged endurance performance in cycling. Seven male subjects, accustomed to prolonged endurance cycling, performed 90 min of cycling at ~65% VO(2max) followed by a 16-km time trial 18 h after a 2-h hyperglycemic-hyperinsulinemic clamp (HCC). Hyperglycemia (10 mM) with insulin infused at 300 mU/m(2)/min over a 2-h period resulted in a total glucose uptake of 275 g (assessed by the area under the curve) of which glucose storage accounted for about 73% (i.e. 198 g). Patterns of substrate oxidation during 90-min exercise at 65% VO(2max) were not altered by HCC. Blood glucose and plasma insulin concentrations were higher during exercise after HCC compared with control (p < 0.05) while plasma NEFA was similar. Exercise performance was improved by 49 s and power output was 10-11% higher during the time trial (p < 0.05) after HCC. These data suggest that carbohydrate loading 18 h previously by means of a 2-h HCC improves cycling performance by 3.3% without any change in pattern of substrate oxidation. [ABSTRACT FROM AUTHOR]

To determine if the increases in rectal temperature (T(REC)) during exercise in the heat at a given percent of VO2peak depend on a subject's aerobic fitness level. On three occasions, 10 endurance-trained (Tr) and 10 untrained (UTr) subjects (VO2peak: 60 +/- 6 vs. 44 +/- 3 mL kg(-1) min(-1), P < 0.05) cycled in a hot-dry environment (36 +/- 1 degrees C; 25 +/- 2% humidity, airflow 2.5 m s(-1)) at three workloads (40, 60, and 80% VO2peak). At the same percent of VO2peak, on average, Tr had 28 +/- 5% higher heat production but also higher skin blood flow (29 +/- 3%) and sweat rate (20 +/- 7%; P = 0.07) and lower skin temperature (0.5 degrees C; P < 0.05). Pre-exercise T(REC) was lower in the Tr subjects (37.4 +/- 0.2 vs. 37.6 +/- 0.2; P < 0.05) but similar to the UTr at the end of 40 and 60% VO2peak trials. Thus, exercise T(REC) increased more in the Tr group than in the UTr group (0.6 +/- 0.1 vs. 0.3 +/- 0.1 degrees C at 40% VO2peak and 1.0 +/- 0.1 vs. 0.6 +/- 0.3 degrees C at 60% VO2peak; P < 0.05). At 80% VO2peak not only the increase in T(REC) (1.7 +/- 0.1 vs. 1.3 +/- 0.3 degrees C) but also the final T(REC) was larger in Tr than in UTr subjects (39.15 +/- 0.1 vs. 38.85 +/- 0.1 degrees C; P < 0.05). During exercise in the heat at the same relative intensity, aerobically trained individuals have a larger rise in T(REC) than do the untrained ones which renders them more hyperthermic after high-intensity exercise. [ABSTRACT FROM AUTHOR]

Mechanisms accounting for sex-related differences in the sweat response remain to be elucidated. In the present study, we focused on differences in sweat gland cholinergic sensitivity between males and females. Since, males usually possess higher aerobic capacity than females, we investigated sweating in males and females grouped according to aerobic capacity $$ ({\dot{V}} {\text{O}}_{{2{\text{peak}}}})$$. Forty-four subjects were assigned to four groups: males with higher (MH) and lower (ML), and females with higher (FH) and lower (FL) $$ {\dot{V}} {\text{O}}_{{2{\text{peak}}}}.$$ Forearm sweating was induced by iontophoretic administration (1.5 mA, 60 μA cm−2, 5 min) of pure water or varying concentrations of pilocarpine hydrochloride (0.125, 0.250, 0.5, 1.0 and 2.0%). Local sweat rate (absorbent paper) and the number of activated sweat glands (iodine impregnated paper) were computed. Maximal pilocarpine-induced sweat rate (SRmax) and the pilocarpine concentration which elicited 50% of maximal sweating response ( Km) were calculated. Sweat rate and active gland density increased in response to greater doses of pilocarpine ( p < 0.05). Inter-group differences were evident: SRmax was greatest for MH and lowest for FL ( p < 0.05), but no significant differences were observed between ML and FH ( p = 0.24). Higher SRmax were observed, within-sex, for those with greater aerobic capacity ( p < 0.05). Furthermore, males’ Km values were higher than females’, indicating greater sweat gland affinity for pilocarpine even for groups having similar aerobic capacity ( p < 0.05). In summary, we confirmed that the human sudomotor response is affected by aerobic capacity but, also, that sex-related differences in sweat gland cholinergic sensitivity exist and are not necessarily associated with the typical differences in $$ {\dot{V}} {\text{O}}_{{2{\text{peak}}}}$$ observed between sexes. [ABSTRACT FROM AUTHOR]

This study aimed to test the consistency of using the power required to elicit maximal oxygen uptake during incremental test (P (t)) to demarcate the range of power intensity in the modelling of the power-exhaustion time relationship. Different mathematical procedures were tested using data from ten subjects exercising on a cycle ergometer. After the determination of P (t) and the power at the ventilatory threshold, the subjects did six tests at constant power to exhaustion within 2-15 min. Estimates were obtained from a segmented model using two distinct equations of the anaerobic contribution to power below and above P (t), respectively. This model fit the overall data with a better adequacy than the simple hyperbolic model (standard error of 29.2 +/- 25.2 vs. 42.3 +/- 25.2 s). The power asymptotes were 225.7 +/- 27.3 W from the segmented model, 226.2 +/- 27.3 and 283.3 +/- 20.5 W from the simple model applied to data below and above P (t), respectively. The estimates from the segmented model were strongly correlated with their analogues from the simple model applied only to data below P (t) (R = 1.00 for power asymptote and curvature coefficient). They were not correlated with their analogues from the simple model applied only to data above P (t). These discrepancies between modelling procedures could arise from the method used to determine P (t) and the oversimplification of the oxygen uptake kinetics. These limitations could lead the segmented model to an overestimation of the anaerobic contribution which was around 15% of total energy expended at P (t). [ABSTRACT FROM AUTHOR]

An extended exponential exercise protocol was validated by comparing submaximal and maximal parameters with those obtained by linear protocol. Normal subjects (n = 16, 20-69 years) undertook maximal exercise tests on treadmill and cycle ergometer. The subjects had a wide range of exercise capacity, and all were accommodated by the protocol. Mean oxygen uptake (V(O2)) agreed between protocols at gas exchange anaerobic threshold (theta) (95% CI of difference -0.1 to +0.06 l min(-1)) and at peak (95% CI of difference -0.1 to +0.1 l min(-1)). Mean pre-thetaDeltaV(O2)/Deltawork rate (W) slope on the cycle ergometer agreed between protocols (95% CI of the difference -0.9 to +0.25 ml min(-1) W(-1)). Post-thetaDeltaV(O2)/DeltaW slope was steeper than pre-theta, and steeper by linear than by exponential protocol (P = 0.0001). It is concluded that the exponential protocol is valid for the measurement of submaximal and maximal exercise parameters in subjects with a wide range of exercise capacity. [ABSTRACT FROM AUTHOR]

This study investigated the energy system contributions of rowers in three different conditions: rowing on an ergometer without and with the slide and rowing in the water. For this purpose, eight rowers were submitted to 2,000 m race simulations in each of the situations defined above. The fractions of the aerobic (W (AER)), anaerobic alactic (W (PCR)) and anaerobic lactic (W ([La-])) systems were calculated based on the oxygen uptake, the fast component of excess post-exercise oxygen uptake and changes in net blood lactate, respectively. In the water, the metabolic work was significantly higher [(851 (82) kJ] than during both ergometer [674 (60) kJ] and ergometer with slide [663 (65) kJ] (P < or = 0.05). The time in the water [515 (11) s] was higher (P < 0.001) than in the ergometers with [398 (10) s] and without the slide [402 (15) s], resulting in no difference when relative energy expenditure was considered: in the water [99 (9) kJ min(-1)], ergometer without the slide [99.6 (9) kJ min(-1)] and ergometer with the slide [100.2 (9.6) kJ min(-1)]. The respective contributions of the W (AER), W (PCR) and W ([La-]) systems were water = 87 (2), 7 (2) and 6 (2)%, ergometer = 84 (2), 7 (2) and 9 (2)%, and ergometer with the slide = 84 (2), 7 (2) and 9 (1)%. VO2, HR and lactate were not different among conditions. These results seem to indicate that the ergometer braking system simulates conditions of a bigger and faster boat and not a single scull. Probably, a 2,500 m test should be used to properly simulate in the water single-scull race. [ABSTRACT FROM AUTHOR]

We investigated the impact of 13 days of "living high-training low" (LHTL) on the antioxidant/prooxidant balance in elite endurance swimmers. Eighteen elite swimmers from the French Swimming Federation were submitted to a 13-day endurance training and divided into two groups: one group trained at 1,200 m and lived in hypoxia (2,500-3,000 m simulated altitude) and the second group trained and lived at 1,200 m. The subjects performed an acute hypoxic test (10 min at 4,800 m) before and 1 day after the training period. Plasma levels of advanced oxidation protein products (AOPP), malondialdehydes (MDA), ferric reducing antioxidant power (FRAP), and lipid-soluble antioxidants were measured before and after the 4,800 m tests. After the training, MDA and AOPP responses to the 4,800 m test were lower than before training for both groups (+10 vs. +2%; P = 0.01 for MDA and +80 vs. +14%; P = 0.01 for AOPP). Thirteen days of LHTL did not modify antioxidant status (FRAP and lipid-soluble antioxidants) despite intakes in vitamins A and E below the recommended daily allowances. The LHTL did not affect the antioxidant status in elite swimmers; however, the normoxic endurance training induced preconditioning mechanisms in response to the 4,800 m test. [ABSTRACT FROM AUTHOR]

Investigations of training effects on exercise energy cost have yielded conflicting results. The purpose of the present study was to compare quadriceps energy cost and oxidative capacity between endurance-trained and sedentary subjects during a heavy dynamic knee extension exercise. We quantified the rates of ATP turnover from oxidative and anaerobic pathways with (31)P-MRS, and we measured simultaneously pulmonary oxygen uptake in order to assess both total ATP production [i.e., energy cost (EC)] and O(2) consumption (O(2) cost) scaled to power output. Seven sedentary (SED) and seven endurance-trained (TRA) subjects performed a dynamic standardized rest-exercise-recovery protocol at an exercise intensity corresponding to 35% of maximal voluntary contraction. We showed that during a dynamic heavy exercise, the O(2) cost and EC were similar in the SED and endurance-trained groups. For a given EC, endurance-trained subjects exhibited a higher relative mitochondrial contribution to ATP production at the muscle level (84 +/- 12% in TRA and 57 +/- 12% in SED; P < 0.01) whereas the anaerobic contribution was reduced (18 +/- 12% in TRA and 44 +/- 11% in SED; P < 0.01). Our results obtained in vivo illustrate that on the one hand the beneficial effects of endurance training are not related to any reduction in EC or O(2) cost and on the other hand that this similar EC was linked to a change regarding the contribution of anaerobic and oxidative processes to energy production, i.e., a greater aerobic energy contribution associated with a concomitant reduction of the anaerobic energy supply. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study evaluated energy cost and energy sources of a ballet exercise ( grand adage) in young female dancers with different technical ability, and then related the energy sources to the subject’s $$ \ifmmode\expandafter\dot\else\expandafter\.\fi{V}{\text{O}}_{{2\max }} $$ and anaerobic threshold (IAT). Twenty-five dancers (13–16 years) were divided into two different technical ability groups: low-level ( n = 13) and high-level ( n = 12). The overall energy requirement of dance exercise ( VO2eq) was obtained by adding the amount of VO2 during exercise above resting (aerobic source or VO2ex) to the VO2 up to the fast component of recovery (anaerobic alactic source or VO2al) and to the energy equivalent of peak blood lactate accumulation (anaerobic lactic source or $$ V\text{O}_{\text{2la}^{-}} $$ ) of recovery. VO2eq of exercise amounted to 81 ± 10 and 94 ± 9 ml kg−1 in low-level and high-level groups, respectively. VO2ex represented the higher fraction (65 ± 4% and 77 ± 5%) in low-level and high-level groups, respectively, of VO2eq in both the groups. In the low-level group the remaining fractions were: 23 ± 2 % for VO2al and 12 ± 1% for $$ V\text{O}_{\text{2la}^{-}} $$ . In high-level group the remaining fractions were: 18 ± 2 % for VO2al and 4 ± 1% for $$ V\text{O}_{\text{2la}^{-}} $$ . Between two groups, significant differences were found in VO2ex ( P < 0.01), $$ V\text{O}_{\text{2la}^{-}} $$ ( P < 0.01), and VO2al ( P < 0.05). IAT was 55 and 60% of $$ \ifmmode\expandafter\dot\else\expandafter\.\fi{V}{\text{O}}_{{2\max }} $$ for low-level and high-level dancers, respectively. Low-level dancers performed more exercise above IAT than high-level. For these reasons, it should be better to define exercise intensity according to the IAT parameter and not only to $$ \ifmmode\expandafter\dot\else\expandafter\.\fi{V}{\text{O}}_{{2\max }} . $$ [ABSTRACT FROM AUTHOR]

To further understand the mechanism(s) explaining the faster pulmonary oxygen uptake $$(p{\dot{V}}\hbox{O}_{2})$$ kinetics found in children compared to adults, this study examined whether the phase II $$p{\dot{V}}\hbox{O}_{2}$$ kinetics in children are mechanistically linked to the dynamics of intramuscular PCr, which is known to play a principal role in controlling mitochondrial oxidative phosphorylation during metabolic transitions. On separate days, 18 children completed repeated bouts of moderate intensity constant work-rate exercise for determination of (1) PCr changes every 6 s during prone quadriceps exercise using 31P-magnetic resonance spectroscopy, and (2) breath by breath changes in $$p{\dot{V}}\hbox{O}_{2}$$ during upright cycle ergometry. Only subjects ( n = 12) with 95% confidence intervals ≤±7 s for all estimated time constants were considered for analysis. No differences were found between the PCr and phase II $$p{\dot{V}}\hbox{O}_{2}$$ time constants at the onset (PCr 23 ± 5 vs. $$p{\dot{V}}\hbox{O}_{2}\ 23 \pm 4\,\hbox{s}, P=1.000)$$ or offset (PCr 28 ± 5 vs. $$p{\dot{V}}\hbox{O}_{2}\ 29 \pm 5\,\hbox{s},\, P=1.000)$$ of exercise. The average difference between the PCr and phase II $$p{\dot{V}}\hbox{O}_{2}$$ time constants was 4 ± 4 s for the onset and offset responses. Pooling of the exercise onset and offset responses revealed a significant correlation between the PCr and $$p{\dot{V}}\hbox{O}_{2}$$ time constants ( r = 0.459, P = 0.024). The close kinetic coupling between the $$p{\dot{V}}\hbox{O}_{2}$$ and PCr responses at the onset and offset of exercise in children is consistent with our current understanding of metabolic control and suggests that an age-related modulation of the putative phosphate linked controller(s) of mitochondrial oxidative phosphorylation may explain the faster $$p{\dot{V}}\hbox{O}_{2}$$ kinetics found in children compared to adults. [ABSTRACT FROM AUTHOR]

Obesity and type 2 diabetes (T2D) are associated with abnormal cardiovascular autonomic function and increased risk for cardiac complications, especially after exercise. Since improvements at rest are not always observed after training, we investigated changes in resting and post-exercise autonomic function in obese women with and without T2D after16-week of walking training. Heart rate (HR) variability (HRV) and baroreflex sensitivity (BRS) were measured at rest and 20 min after a 20 min bout of treadmill exercise at 65% VO(2) peak in obese women with (n = 8) and without T2D (n = 12) before and after training. HRV was analyzed by frequency-domain [high- (HF) power and low-frequency (LF)] and BRS by the sequence method. Exercise training induced similar significant changes in VO(2) peak, resting systolic blood pressure (SBP) and post-exercise autonomic function in both groups. Training increased VO(2 )peak (6%; P < 0.01) and decreased resting SBP (8%; P < 0.001). Increased post-exercise HR recovery (5%; P < 0.001), HF power (14%; P < 0.05), LF power (14%; P < 0.05) and BRS (86%; P < 0.001) were also observed. Resting autonomic function and post-exercise SBP were not altered after training. In conclusion, endurance training reduced blood pressure without changes in HRV and BRS at rest, but training increased HRV and BRS during the recovery of acute endurance exercise indicating an improved post-exercise autonomic modulation of HR, which was similar in obese women with and without T2D. [ABSTRACT FROM AUTHOR]

In older healthy men, aerobic exercise capacity is related to postischemic flow-mediated dilation of the brachial artery (FMD), but corresponding data in a younger population is not available. In addition, whether submaximal aerobic exercise performance also correlates with this kind of vasomotor reactivity is not known. Therefore, in 15 nonsmoking young healthy men [age 27 (5) years; body mass index: 24 (2) kg/m(2); mean (SD)] with different levels of ordinary physical activity, but not performing upper-extremity training, we measured FMD at 1 min after reactive hyperemia, and pulmonary oxygen uptake (VO(2)) at ventilatory anaerobic threshold (VO(2)AT) and at peak effort (peak VO(2)) during an incremental exercise on a treadmill. In our participants, FMD was 9.1 (3.4)%, VO(2)AT was 40.72 (5.92) ml/kg per min, and peak VO(2) was 52.95 (8.13) ml/kg per min. Using bivariate Pearson's correlation, and in separate multivariate regression analyses, VO(2)AT and peak VO(2) showed a significant and reasonably good correlation with FMD (r = 0.84, P < 0.001 and r = 0.77, P = 0.001, respectively), independent of age, body mass index and serum total cholesterol (beta = 0.77, P < 0.001, R(2) of the overall model = 0.79 and beta = 0.70, P < 0.005, R(2) of the overall model = 0.69, respectively). Our data provide evidence suggesting that in young healthy men a higher submaximal and maximal aerobic exercise performance is associated with a greater FMD of peripheral conduit arteries. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the relationship between physical fitness, heart rate variability (HRV) and cognitive function in 37 male sailors from the Royal Norwegian Navy. All subjects participated in an 8-week training program, after which the subjects completed the initial cognitive testing (pretest). The subjects were assigned into a detrained group (DG) and a trained group (TG) based on their application for further duty. The DG withdrew from the training program for 4 weeks after which all subjects then completed the cognitive testing again (post-test). Physical fitness, measured as maximum oxygen consumption (VO2(max)), resting HRV, and cognitive function, measured using a continuous performance task (CPT) and a working memory test (WMT), were recorded during the pre-test and the post-test, and the data presented as the means and standard deviations. The results showed no between-group differences in VO2(max) or HRV at the pre-test. The DG showed a significant decrease in VO2(max) from the pre- to the post-test and a lower resting HRV than the TG on the post-test. Whereas there were no between-group differences on the CPT or WMT at the pre-test, the TG had faster reaction times and more true positive responses on tests of executive function at the post-test compared to the pre-test. The DG showed faster reaction times on non-executive tasks at the post-test compared to the pre-test. The results are discussed within a neurovisceral integration framework linking parasympathetic outflow to the heart to prefrontal neural functions. [ABSTRACT FROM AUTHOR]

There is still considerable debate and some confusion as to the most appropriate method of scaling or normalizing maximum oxygen uptake (VO2max) for differences in body mass (m) in both adults and children. Previous studies on adult populations have demonstrated that although the traditional ratio standard VO2max (ml kg(-1) min(-1)) fails to render VO2max independent of body mass, the ratio standard is still the best predictor of running performance. However, no such evidence exists in children. Hence, the purpose of the present study was to investigate whether the ratio standard is still the most appropriate method of normalising VO2max to predict 1-mile run speed in a group of 12-year-old children (n=36). Using a power function model and log-linear regression, the best predictor of 1-mile run speed was given by: speed (m s(-1))=55.1 VO2max(0.986) m(-0.96). With both the VO2max and body mass exponents being close to unity but with opposite signs, the model suggest the best predictor of 1-mile run speed is almost exactly the traditional ratio standard recorded in the units (ml kg(-1) min(-1)). Clearly, reporting the traditional ratio standard VO2max, recorded in the units (ml kg(-1) min(-1)), still has an important place in publishing the results of studies investigating cardiovascular fitness of both children and adults. [ABSTRACT FROM AUTHOR]