Reduced volume but increased training intensity elevates muscle Na+-K+ pump alpha1-subunit and NHE1 expression as well as short-term work capacity in humans
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The present study examined muscle adaptations and alterations in work capacity in endurance-trained runners after a change from endurance to sprint training. Fifteen runners were assigned to either a sprint training (ST, n = 8) or a control (CON, n = 7) group. ST replaced their normal training by 30-s sprint runs three to four times a week, whereas CON continued the endurance training ( approximately 45 km/wk). After the 4-wk sprint period, the expression of the muscle Na(+)-K(+) pump alpha(1)-subunit and Na(+)/H(+)-exchanger isoform 1 was 29 and 30% higher (P < 0.05), respectively. Furthermore, plasma K(+) concentration was reduced (P < 0.05) during repeated intense running. In ST, performance in a 30-s sprint test, Yo-Yo intermittent recovery test, and two supramaximal exhaustive runs was improved (P < 0.05) by 7, 19, 27, and 19%, respectively, after the sprint training period, whereas pulmonary maximum oxygen uptake and 10-k time were unchanged. No changes in CON were observed. The present data suggest a role of the Na(+)-K(+) pump in the control of K(+) homeostasis and in the development of fatigue during repeated high-intensity exercise. Furthermore, performance during intense exercise can be improved and endurance performance maintained even with a reduction in training volume if the intensity of training is very high.
|Tidsskrift||American Journal of Physiology: Regulatory, Integrative and Comparative Physiology|
|Status||Udgivet - 2008|
CURIS 2008 5200 003