Failure of hypoxia to exaggerate the metabolic stress in working muscle following short-term training.
This study investigated the effects of hypoxia (experiment 1) and the effects of hypoxia following short-term training (experiment 2) on metabolism in working muscle. In experiment 1, eight males with a peak aerobic power (VO2peak) of 45 +/- 1.7 ml x kg(-1) x min(-1) (x +/- SE) cycled for 15 min at 66.1 +/- 2.1% VO2peak while breathing room air [normoxia (N)] or 14% O(2) [hypoxia (H)]. In experiment 2, nine males with a VO2peak of 43.3 +/- 1.6 ml x kg(-1) x min(-1) performed a similar protocol at 60.7 +/- 1.4% VO2peak during N and during H following 5 days of submaximal exercise training (H + T). Tissue samples extracted from the vastus lateralis before exercise and at 1, 3, and 15 min of exercise indicated that compared with N, H resulted in lower (P < 0.05) concentrations (mmol/kg dry wt) of creatine phosphate and higher (P < 0.05) concentrations of creatine, inorganic phosphate, and lactate, regardless of exercise time. When the exercise was performed at H + T and compared with N, no differences were observed in creatine phosphate, creatine, inorganic phosphate, and lactate, regardless of duration. Given the well-documented effects of the short-term training model on elevating VO2 kinetics and attenuating the alterations in high-energy phosphate metabolism and lactate accumulation, it would appear that the mechanism underlying the reversal of these adaptations during H is linked to a more rapid increase in oxidative phosphorylation, mediated by increased oxygen delivery and/or mitochondrial activation.
Green
H J
HJ
Dept. of Kinesiology, Univ. of Waterloo, Waterloo, ON, N2L3G1, Canada. green@healthy.uwaterloo.ca
Burnett
M E
ME
Smith
I C
IC
Tupling
S M
SM
Ranney
D A
DA
D000222:Adaptation, Physiological; D000227:Adenine Nucleotides / Q000378:metabolism; D001642:Bicycling; D015444:Exercise; D005947:Glucose / Q000378:metabolism; D006019:Glycolysis; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D007291:Inosine Monophosphate / Q000378:metabolism; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism; D009119:Muscle Contraction; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption; D010725:Phosphocreatine / Q000378:metabolism; D011659:Pulmonary Gas Exchange; D052097:Quadriceps Muscle / Q000378:metabolism* / Q000503:physiopathology; D013312:Stress, Physiological; D013997:Time Factors; D055815:Young Adult
D000227:Adenine Nucleotides; D010725:Phosphocreatine; D007291:Inosine Monophosphate; D019344:Lactic Acid; D005947:Glucose