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Am J Physiol Regul Integr Comp Physiol 297: R877-R884, 2009. First published July 15, 2009; doi:10.1152/ajpregu.90848.2008
0363-6119/09 $8.00
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ARTICLES

Prior heavy exercise elevates pyruvate dehydrogenase activity and muscle oxygenation and speeds O2 uptake kinetics during moderate exercise in older adults

Brendon J. Gurd,1,2 Sandra J. Peters,6 George J. F. Heigenhauser,5 Paul J. LeBlanc,6 Timothy J. Doherty,4 Donald H. Paterson,1,2 and John M. Kowalchuk1,2,3

1Canadian Centre for Activity and Aging, 2School of Kinesiology, Faculty of Health Sciences, 3Department of Physiology and Pharmacology, and 4Departments of Clinical Neurological Sciences and Rehabilitation Medicine, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada; 5Department of Medicine, McMaster University, Hamilton, Ontario, Canada; and 6Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, Canada

Submitted 21 October 2008 ; accepted in final form 14 July 2009

The adaptation of pulmonary oxygen uptake (VO2p) kinetics during the transition to moderate-intensity exercise is slowed in older compared with younger adults; however, this response is faster following a prior bout of heavy-intensity exercise. We have examined VO2p kinetics, pyruvate dehydrogenase (PDH) activation, muscle metabolite contents, and muscle deoxygenation in older adults [n = 6; 70 ± 5 (67–74) yr] during moderate-intensity exercise (Mod1) and during moderate-intensity exercise preceded by heavy-intensity warm-up exercise (Mod2). The phase 2 VO2p time constant ({tau}VO2p) was reduced (P < 0.05) in Mod2 (29 ± 5 s) compared with Mod1 (39 ± 14 s). PDH activity was elevated (P < 0.05) at baseline prior to Mod2 (2.1 ± 0.6 vs. 1.2 ± 0.3 mmol acetyl-CoA·min–1·kg wet wt–1), and the delay in attaining end-exercise activity was abolished. Phosphocreatine breakdown during exercise was reduced (P < 0.05) at both 30 s and 6 min in Mod2 compared with Mod1. Near-infrared spectroscopy-derived indices of muscle oxygenation were elevated both prior to and throughout Mod2, while muscle deoxygenation kinetics were not different between exercise bouts consistent with elevated perfusion and O2 availability. These results suggest that in older adults, faster VO2p kinetics following prior heavy-intensity exercise are likely a result of prior activation of mitochondrial enzyme activity in combination with elevated muscle perfusion and O2 availability.

VO2 kinetics; ageing; pyruvate dehydrogenase; phosphocreatine


Address for reprint requests and other correspondence: J. M. Kowalchuk, Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, HSB 411C, The Univ. of Western Ontario, London, Ontario, Canada N6A 5B9 (e-mail: jkowalch{at}uwo.ca)






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