Sprint training increased the capacity for muscular work and improved muscle strong ion regulation during exercise. Increased muscle Na+ and K+ uptake during exercise after training are consistent with a greater activation of the muscle Na+-K+ pump, reduced cellular K+ loss and the observed reduced rate of fatigue. There was little evidence of enhanced glycolysis after training, suggesting that the major energetic adaptation after sprint training was enhanced aerobic metabolism. A consequence of the improved muscle strong ion regulation was a lower arterial plasma [SID] due to lower plasma [K+] and [Na+], and higher plasma [Lac-], resulting in a greater plasma acidosis. Thus, sprint training improved muscle ion regulation, associated with increased intense exercise performance, at the expense of a greater systemic acidosis.
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