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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 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]