EFFECTS OF INTENSIFIED ENDURANCE TRAINING ON THE CONCENTRATION OF NA,K-ATPASE AND CA-ATPASE IN HUMAN SKELETAL-MUSCLE

Thirty-nine moderately endurance trained males increased their normal training programme of 2.2 h week(-1) with an average training intensit y of 65 % of maximum heart rate (HR(max)) to 2.7 h week(-1) and a mean intensity of 78 % of HR(max). Performance tests and measurements of t he total concentrations of Na,K-ATPase (H-3-ouabain binding) and Ca-AT Pase, fibre type distribution and fibre area were performed in biopsie s from the vastus lateralis muscle before and after increased training . The 6 weeks of training elevated Vo2(max) from 54.9 +/- 3.1 to 58.3 +/- 3.0 ml O-2 min(-1) kg(-1) (P < 0.0001). Exercise time to exhaustio n at 86 % of Vo(2max) (pre-training) increased from 35 +/- 8 to 61 +/- 17 min (P < 0.0001). The concentration of Ca-ATPase was unaffected by the intensified training (6.74 +/- 1.03 vs. 6.68 +/- 1.07 nmol g wet wt(-1)), but the concentration of Na,K-ATPase increased from 307 +/- 4 3 to 354 +/- 59 pmol g wet wt(-1) (P < 0.0001). Therelative distributi on of FT-fibres was correlated with the concentration of Ca-ATPase (r = 0.72, P < 0.0001). The data support the view that intensive training induces an upregulation of the concentration of skeletal muscle Na,K- ATPase, but no change in the total capacity for reaccumulation of Ca2 into the SR. There was no correlation between the concentrations of N a,K-ATPase, Ca-ATPase and indices of endurance performance.