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1 Exercise Metabolism Group, School of Medical Sciences, RMIT University, Melbourne, Victoria, Australia
2 Muscle Ions & Exercise Group, School of Human Movement, Recreation and Performance, Centre for Rehabilitation, Exercise & Sport Science, Victoria University of Techonology, Melbourne, Victoria, Australia
3 Physiology, Australian Institute of Sport, Canberra, ACT, Australia
4 School of Exercise and Sport Science, The University of Sydney, Sydney, NSW, Australia
* To whom correspondence should be addressed. E-mail: john.hawley{at}rmit.edu.au.
We determined the effect of 20 nights of live-high, train-low (LHTL) hypoxic exposure on lactate kinetics, monocarboxylate lactate transporter proteins (MCT1 and MCT4) and muscle in-vitro buffering capacity (
m) in well-trained athletes. 29 trained cyclists/triathletes were divided into one of three groups: 20 consecutive nights of hypoxic exposure (LHTLc), 20 nights of intermittent hypoxic exposure (four 5-night blocks of hypoxia, each interspersed with 2 nights of normoxia, (LHTLi), or control (CON). Rates of lactate appearance (Ra), and disappearance (Rd) were determined from a primed, continuous infusion of L-[U-14C]-lactic acid tracer during 90 minutes of steady-state exercise (60 min at 65% VO2peak followed by 30 min at 85% VO2peak). A resting muscle biopsy was taken pre and post 20 nights of LHTL for the determination of m and MCT1 and MCT4 protein abundance. Ra during the first 60 min of exercise was not different between groups. During the last 25 min of exercise at 85% VO2peak Ra was higher compared with exercise at 65% of VO2peak, and was decreased in LHTLc (P<0.05) compared with the other groups. Rd followed a similar pattern to Ra. Although Rox was significantly increased during exercise at 85% compared to 65% of VO2peak, there were no differences between the three groups or across trials. There was no effect of hypoxic exposure on m or MCT1 and MCT4 protein abundance. We conclude that 20 nights of continuous hypoxia exposure decreased whole-body Ra during intense exercise in well-trained athletes. However, muscle markers of lactate metabolism and pH regulation. Were unchanged by the LHTL intervention.
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