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L-Ornithine plays an important role in ammonia metabolism via the urea cycle. This study aimed to examine the effect of L-ornithine hydrochloride ingestion on ammonia metabolism and performance after intermittent maximal anaerobic cycle ergometer exercise. Ten healthy young adults (age, 23.8 ± 3.9 year; height, 172.3 ± 5.5 cm; body mass, 67.7 ± 6.1 kg) with regular training experience ingested L-ornithine hydrochloride (0.1 g/kg, body mass) or placebo after 30 s of maximal cycling exercise. Five sets of the same maximal cycling exercise were conducted 60 min after ingestion, and maximal cycling exercise was conducted after a 15 min rest. The intensity of cycling exercise was based on each subject's body mass (0.74 N kg(-1)). Work volume (watt), peak rpm (rpm) before and after intermittent maximal ergometer exercise and the following serum parameters were measured before ingestion, immediately after exercise and 15 min after exercise: ornithine, ammonia, urea, lactic acid and glutamate. Peak rpm was significantly greater with L-ornithine hydrochloride ingestion than with placebo ingestion. Serum ornithine level was significantly greater with L-ornithine hydrochloride ingestion than with placebo ingestion immediately and 15 min after intermittent maximal cycle ergometer exercise. In conclusion, although maximal anaerobic performance may be improved by L-ornithine hydrochloride ingestion before intermittent maximal anaerobic cycle ergometer exercise, the above may not depend on increase of ammonia metabolism with L-ornithine hydrochloride. [ABSTRACT FROM AUTHOR]

Nutrition is an important co-factor in exercise-induced training adaptations in muscle. We compared the effect of 6 weeks endurance training (3 days/week, 1-2 h at 75% VO(2peak)) in either the fasted state (F; n = 10) or in the high carbohydrate state (CHO, n = 10), on Ca(2+)-dependent intramyocellular signalling in young male volunteers. Subjects in CHO received a carbohydrate-rich breakfast before each training session, as well as ingested carbohydrates during exercise. Before (pretest) and after (posttest) the training period, subjects performed a 2 h constant-load exercise bout (~70% of pretest VO(2peak)) while ingesting carbohydrates (1 g/kg h(-1)). A muscle biopsy was taken from m. vastus lateralis immediately before and after the test, and after 4 h of recovery. Compared with pretest, in the posttest basal eukaryotic elongation factor 2 (eEF2) phosphorylation was elevated in CHO (P < 0.05), but not in F. In the pretest, exercise increased the degree of eEF2 phosphorylation about twofold (P < 0.05), and values returned to baseline within the 4 h recovery period in each group. However, in the posttest dephosphorylation of eEF2 was negated after recovery in CHO, but not in F. Independent of the dietary condition training enhanced the basal phosphorylation status of Phospholamban at Thr(17), 5'-AMP-activated protein kinase α (AMPKα), and Acetyl CoA carboxylase β (ACCβ), and abolished the exercise-induced increase of AMPKα and ACCβ (P < 0.05). In conclusion, training in the fasted state, compared with identical training with ample carbohydrate intake, facilitates post-exercise dephosphorylation of eEF2. This may contribute to rapid re-activation of muscle protein translation following endurance exercise. [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]

This study investigated the effect of repeated bouts of short-term, high-intensity cycling exercise on the salivary cortisol, testosterone and immunoglobulin (A) concentrations of 15-16 year old boys. Seventeen apparently healthy schoolchildren (aged 15.5 +/- 0.4 years) participated in this study. All participants completed 6 x 8 s sprints, interspersed with 30 s recovery intervals on a cycle ergometer. Using the passive drool method, salivary samples were taken before, and 5 min after, exercise. The group mean for peak power output was 723.1 +/- 180.3 s. There were significant changes (p < or = 0.05) in both SalT and SalC, 5 min after completing 6 x 8 s cycle sprints. No significant differences (p > 0.05) were recorded for SIg(A). The increases in SalT and SalC reported in this study confirm that repeated bouts of short-term, high-intensity exercise produces significant physiological hormonal responses in adolescent boys, but does not affect mucosal immune function. [ABSTRACT FROM AUTHOR]

The aim was to test the hypothesis that one night of sleep deprivation will impair pre-loaded 30 min endurance performance and alter the cardio-respiratory, thermoregulatory and perceptual responses to exercise. Eleven males completed two randomised trials separated by 7 days: once after normal sleep (496 (18) min: CON) and once following 30 h without sleep (SDEP). After 30 h participants performed a 30 min pre-load at 60% [VO(2 max) followed by a 30 min self-paced treadmill distance test. Speed, RPE, core temperature (T(re)), mean skin temperature (T(sk)), heart rate (HR) and respiratory parameters VO(2 max), VCO(2), VE, RER pre-load only) were measured. Less distance (P = 0.016, d = 0.23) was covered in the distance test after SDEP (6037 (759) 95%CI 5527 to 6547 m) compared with CON (6224 (818) 95%CI 5674 to 6773 m). SDEP did not significantly alter T(re) at rest or thermoregulatory responses during the pre-load including heat storage (0.8 degrees C) and T(sk). With the exception of raised VO(2) at 30 min on the pre-load, cardio-respiratory parameters, RPE and speed were not different between trials during the pre-load or distance test (distance test mean HR, CON 174 (12), SDEP 170 (13) beats min(-1): mean RPE, CON 14.8 (2.7), SDEP 14.9 (2.6)). In conclusion, one night of sleep deprivation decreased endurance performance with limited effect on pacing, cardio-respiratory or thermoregulatory function. Despite running less distance after sleep deprivation compared with control, participants' perception of effort was similar indicating that altered perception of effort may account for decreased endurance performance after a night without sleep. [ABSTRACT FROM AUTHOR]

The present study was undertaken to evaluate the acute effect of prior resistance training of varying intensities on energy expenditure and substrate utilization during subsequent aerobic exercise. Eleven males and 21 females completed three experimental trials consisting of (1) aerobic exercise only (C), (2) aerobic exercise preceded by a high-intensity resistance training (HI), and (3) aerobic exercise preceded by a low-intensity resistance training (LO). Resistance training produced an equal volume between HI and LO and consisted of six exercises with each performed for three sets of eight repetitions at 90% of 8-RM in HI and three sets of 12 repetitions at 60% of 8-RM in LO. Aerobic exercise was performed on a cycle ergometer at 50% VO(2)peak for 20 min in all trials. Oxygen uptake (VO2), and carbohydrate and fat oxidation were determined throughout each aerobic exercise session. Fat oxidation rate was higher (P < 0.05) in HI than either LO or C in both males and females. VO2 was also higher (P < 0.05) in HI than either LO or C in females. In males, although between-trial differences in VO2 did not reach statistical significance, they were consistent with the trend seen in females. No differences in carbohydrate oxidation rates were observed across the three trials in either gender group. It appears that in training that combines both aerobic and resistance exercises, performing a comparatively higher intensity resistance exercise first would augment fat utilization and energy expenditure during subsequent aerobic exercise. [ABSTRACT FROM AUTHOR]

The reduced arterial oxygen tension at high altitude impairs the ability to work. Acetazolamide improves arterial oxygen saturation (SaO2) by increasing ventilation but is associated with an increased work and cost of breathing. Depending on the settings, sildenafil can also increases SaO2 possibly through a reduction in pulmonary hypertension and interstitial edema, which could improve ventilation–perfusion matching. The objective of this study is to determine the effects of acetazolamide and sildenafil on ventilatory control and breathing efficiency ( VE/ VCO2) during submaximal steady-state hypoxic exercise in healthy individuals. Following 18 h of hypoxic exposure in an altitude tent at an oxygen concentration of 12.5% (simulated altitude of 4,300 m), 15 participants performed 10 min of hypoxic exercise on a stationary bicycle at 40% of their sea level peak oxygen uptake ( VO2) while randomly receiving sildenafil 40 mg (SIL), acetazolamide 125 mg (ACZ) or a placebo (PLA). There was no difference in VO2 during exercise between conditions while SaO2 was greater with acetazolamide compared to both placebo and sildenafil. Acetazolamide increased ventilation (PLA 49.0 ± 3.2, SIL 47.7 ± 3.1, ACZ 52.1 ± 3.0 l/min) and reduced end-tidal CO2 ( PETCO2) (PLA 32.1 ± 0.8, SIL 32.8 ± 0.9, ACZ 29.2 ± 0.7 mmHg) compared to placebo and sildenafil. Breathing was less efficient with acetazolamide (increased VE/ VCO2) in comparison to placebo and sildenafil (PLA 41.5 ± 1.0, SIL 40.4 ± 1.3, ACZ 45.4 ± 1.0) while sildenafil did not change VE/ VCO2 during hypoxic exercise. In conclusion, acetazolamide increased ventilation and reduced breathing efficiency while sildenafil did not affect breathing efficiency despite a trend toward a blunted ventilatory response, possibly due to a reduction in pulmonary hypertension and/or ventilatory drive, during submaximal hypoxic exercise in healthy individuals. [ABSTRACT FROM AUTHOR]

The aims of this study were to evaluate the effects of both noncircular (ROT) and conventional (CON) chainring systems on aerobic and anaerobic cycling performances of professional cyclists, while analyzing the influence of varying the crank angle of maximum crank arm length of ROT. Fifteen professional road cyclists performed both incremental and sub-maximal aerobic tests and the Wingate anaerobic test in the laboratory. There were no statistical differences between CON and ROT in the aerobic tests, even when the best ROT position (ROT+) was selected. However, in the anaerobic test, maximal (4.2-9.1%) and mean (0.7-4.7%) power outputs were higher in ROT (P < 0.05). These differences were greater when the ROT+ was selected (11.2 and 7.0%, respectively). Our findings suggest that ROT is able to improve anaerobic but not aerobic cycling performance in professional cyclists. Nevertheless, it must be adapted to each cyclist to ensure these improvements. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the methodology of Margaria staircase test (MT) for assessment of muscle anaerobic power. Specifically, we hypothesized that due to the scaling effects the outcome of MT calculated using the standard formula that suggests the power output to be proportional to body mass [P = (m . g . h)/T; P = power output, m = body mass, g = 9.81 m/s(2), h = height of stairs climbed, T = running time] overestimates the effect of body size on the calculated muscle power output. Young and physically active subjects (N = 111) were tested and the relationship between P and body size (S; either body mass or height) was assessed by standard allometric model (i.e., P = a . S ( b ); where a and b were the constant multiplier and allometric parameter, respectively). The results supported the hypothesized relationship by revealing b = 0.66 (95%CI = 0.49-0.83; r = 0.59; P < 0.001) and b = 1.13 (95%CI = 0.49-0.83; r = 0.34; P < 0.001) for body mass and body height, respectively. The obtained values of b (i.e., b < 1 for body mass and b < 3 for body height) suggest that the standard formula of MT overestimates the power output of larger subjects and underestimates the power of smaller ones. Since the results were mainly in line with both the experimental findings and theoretical predictions regarding the general effects of scale on human muscle power, we propose a modified formula that provides normalized power: P ( n ) = P/m (0.67) = [(m . g . h)/T]/m (0.67) = (m (0.33) . g . h)/T. The modified formula could provide a body size independent index of muscle power that would both allow for establishing standards and enable comparison of individuals and groups of individuals of different body dimensions. [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]

It has been well demonstrated that the principal factor responsible for oxidative damage during exercise is the increase in oxygen consumption. However, other theoretical factors (acidosis, catecholamine autoxidation, ischemia-reperfusion syndrome, etc.) that are known to induce, in vitro, oxidative damage may also be operative during short-term supramaximal anaerobic exercise. Therefore, we hypothesized that short-term supramaximal anaerobic exercise (30-s Wingate test) could induce an oxidative stress. Lipid peroxidation markers [serum lipid radical production detected by electron spin resonance (ESR) spectroscopy and plasma malondialdehyde (MDA) levels detected by the thiobarbituric acid reactive substances (TBARS) method], as well as erythrocyte antioxidant enzyme activities [glutathione peroxidase (GPx), superoxide dismutase (SOD)] and erythrocyte glutathione (GSH) levels, were measured at rest, after the Wingate test and during the 40 min of recovery. The recovery of exercise was associated with a significant increase (x2.7) in lipid radical production detected by ESR spectroscopy, as well as with changes in the erythrocyte GSH level (-13.6%) and SOD activity (-11.7%). The paradoxical decrease in plasma TBARS (-23.7%) which was correlated with the peak power developed during the Wingate test ( r=-0.7), strongly suggests that such exercise stimulates the elimination of MDA. In conclusion, this study demonstrates that short-term supramaximal anaerobic exercise induces an oxidative stress and that the plasma TBARS level is not a suitable marker during this type of exercise. [ABSTRACT FROM AUTHOR]