Brooks, G. A., Wolfel, E. E., Groves, B. M., Bender, P. R., Butterfield, G. E., Cymerman, A., Mazzeo, R. S., Sutton, J. R., Wolfe, R. R., & Reeves, J. T. (1992). Muscle accounts for glucose disposal but not blood lactate appearance during exercise after acclimatization to 4,300 m. Journal of Applied Physiology, 72, 2435-2445.
Seven healthy males were studied at sea-level, upon arriving at altitude (4,300 m), and after three weeks of acclimatization. Glucose and lactate arteriovenous differences across the legs and arms and leg blood flow were measured. Leg glucose uptake increased during exercise at altitude and after acclimatization. Legs accounted for all glucose dispersal in exercise. The arms released lactate at all altitudes except during exercise with exposure to altitude, when they consumed lactate. Both active and inactive muscles demonstrated simultaneous lactate extraction and release.
It was concluded that active muscle is the predominant site of glucose disposal during exercise at sea-level and altitude but it is not the sole source of lactate in exercise.
Implication. Lactate accumulated in exercise does not only come from working muscles. Thus, measures taken cannot be inferred to indicate only exercise production. Any inferences will be less than valid or reliable because of this confounding phenomenon. Lactate values should not be used to infer absolute levels of work.
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