LARGE INCREASES IN SKELETAL MUSCLE NA+,K+-ATPASE CONCENTRATION AFTER HIGH INTENSITY SPRINT TRAINING 1318

Abstract

The purpose of this study was to determine the effects of 7 wks of intense interval cycle ergometry training on power output, plasma [K+], muscle excitability and Na+,K+-ATPase concentration. Nine healthy males(22 ± 2 yrs) performed 30s intervals (Wingate protocol) interspersed with 2-4 min recovery 3 times per wk for 7 wks. Brachial arterial and femoral venous plasma [K+] were measured over 4 30s bouts (4 min recovery) pre- and post-training, and needle biopsies taken from vastus lateralis were assayed for vanadate-facilitated [3H)-ouabain binding to determine Na+,K+-ATPase concentration. Training resulted in significant increases in peak power (21.8%), relative power (23.9%) and total work (5%) yet there was no significant change in resting (3.9 ± 0.2 vs 4.0± 0.2 meq/l) or peak (7.01 ± 0.8 vs 7.11 ± 0.7 meq/l) femoral venous plasma [K+]. Muscle excitability, as assessed by the compound muscle action potential, showed no evidence of failure during the 4 30s bouts, and there was no effect of training, indicating a maintenance of muscle excitability. The concentration of Na+,K+-ATPase, however, increased by 55% (229.09 ± 56.4 to 354.08 ± 50.1 pmol/g wet wt) following training. We conclude that the ionic challenge associated with this type of high intensity anaerobic training induces a rapid and profound increase in Na+,K+-ATPase concentration, and the maintenance of sarcolemmal excitability is likely due to the electrogenic nature of the highly active Na+-K+ pump.