title: Prior heavy exercise elevates pyruvate dehydrogenase activity and muscle oxygenation and speeds O2 uptake kinetics during moderate exercise in older adults.
abstract: The adaptation of pulmonary oxygen uptake (VO(2)(p)) 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 VO(2)(p) 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 (Mod(1)) and during moderate-intensity exercise preceded by heavy-intensity warm-up exercise (Mod(2)). The phase 2 VO(2)(p) time constant (tauVO(2)(p)) was reduced (P < 0.05) in Mod(2) (29 +/- 5 s) compared with Mod(1) (39 +/- 14 s). PDH activity was elevated (P < 0.05) at baseline prior to Mod(2) (2.1 +/- 0.6 vs. 1.2 +/- 0.3 mmol acetyl-CoA x min(-1) x 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 Mod(2) compared with Mod(1). Near-infrared spectroscopy-derived indices of muscle oxygenation were elevated both prior to and throughout Mod(2), while muscle deoxygenation kinetics were not different between exercise bouts consistent with elevated perfusion and O(2) availability. These results suggest that in older adults, faster VO(2)(p) kinetics following prior heavy-intensity exercise are likely a result of prior activation of mitochondrial enzyme activity in combination with elevated muscle perfusion and O(2) availability.
authors: Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The Univ. of Western Ontario, London, Ontario, Canada N6A 5B9.
authors: Brendon J
authors: BJ
authors: Gurd
authors: Sandra J
authors: SJ
authors: Peters
authors: George J F
authors: GJ
authors: Heigenhauser
authors: Paul J
authors: PJ
authors: LeBlanc
authors: Timothy J
authors: TJ
authors: Doherty
authors: Donald H
authors: DH
authors: Paterson
authors: John M
authors: JM
authors: Kowalchuk
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000222:Adaptation, Physiological; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000367:Age Factors; D000368:Aged; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000201:enzymology*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010725:Phosphocreatine / Q000378:metabolism; D012123:Pulmonary Ventilation; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D012039:Regional Blood Flow; D019265:Spectroscopy, Near-Infrared; D015854:Up-Regulation
chemical_list: D011768:Pyruvate Dehydrogenase Complex; D010725:Phosphocreatine; D019344:Lactic Acid; D000244:Adenosine Diphosphate; D000105:Acetyl Coenzyme A; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D010100:Oxygen