O2 uptake kinetics, pyruvate dehydrogenase activity, and muscle deoxygenation in young and older adults during the transition to moderate-intensity exercise.

Autor: Gurd, B. J., S. J. Peters, Heigenhauser, G. J. F., LeBlanc, P. J., Doherty, T. J., Paterson, D. H., Kowalchuk, J. M.
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Zdroj: American Journal of Physiology: Regulatory, Integrative & Comparative Physiology; Feb2008, Vol. 294, pR577-R584, 8p, 1 Chart, 1 Graph
Abstrakt: The adaptation of pulmonary O2 uptake (o2p) kinetics is slowed in older compared with young adults during the transition to moderate- intensity exercise. In this study, we examined the relationship between Vo2p kinetics and mitochondrial pyruvate dehydrogenase (PDH) activity in young (n = 7) and older (n = 6) adults. Subjects performed cycle exercise to a work rate corresponding to -90% of estimated lactate threshold. Phase 2 Vo2p kinetics were slower (P < 0.05) in older (T = 40 ± 17 s) compared with young (r = 21 ± 6 s) adults. Relative phosphocreatine (PCr) breakdown was greater (P < 0.05) at 30 s in older compared with young adults. Absolute PCr breakdown at 6 mm was greater (P < 0.05) in older compared with young adults. In young adults, PDH activity increased (P < 0.05) from baseline to 30 s, with no further change observed at 6 mm. In older adults, PDH activity during baseline exercise was similar to that seen in young adults. During the exercise transition, PDH activity did not increase (P> 0.05) at 30 s of exercise but was elevated (P <0.05) after 6 mm. The change in deoxyhemoglobin (HHb) was greater for a given Vo2p in older adults, and there was a similar time course of HHb accompanying the slower Vo2p, kinetics in the older adults, suggesting a slower adaptation of bulk O2 delivery in older adults. In conclusion, the slower adaptation of Vo2p, in older adults is likely a result of both an increased metabolic inertia and lower O2 availability. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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