title: Hard training for 5 mo increases Na(+)-K+ pump concentration in skeletal muscle of cross-country skiers.
abstract: To study how training affects the Na(+)-K+ pump concentration, 11 male and 9 female elite junior cross-country skiers trained 12-15 h/wk at 60-70% (moderate-intensity group) or 80-90% (high-intensity group) of their maximal O2 uptake for 5 mo. Muscle biopsies taken from the vastus lateralis muscle before and after the training period were analyzed for Na(+)-K+ pump concentration by the [3H]ouabain-binding technique. Before training, the concentration was 343 +/- 11 nmol/kg wet muscle mass (mean +/- SE) for the men and 281 +/- 14 nmol/kg for the women (18% less than for the men, P = 0.003). The Na(+)-K+ pump concentration rose by 49 +/- 11 nmol/kg (16%, P < 0.001) for all subjects pooled during the training period, and there was no difference between the two training groups (P = 0.3) or the sexes (P = 0.5) in this increase. The Na(+)-K+ pump concentration correlated with the maximal O2 uptake (r = 0.6, P = 0.003), with the performance during a 20-min treadmill run (r = 0.6, P = 0.003), and to the rank of the subjects' performance as cross-country skiers (Spearman's rank correlation coefficient = 0.76, P < 0.001). These data could mean that for elite cross-country skiers the performance is related to the Na(+)-K+ pump concentration. However, other studies have shown an equally high pump concentration for far less fit subjects, suggesting that the pump concentration may not be a limiting factor.
authors.affiliation: Norwegian University of Sport and Physical Education, Ullevål Hageby, Oslo, Norway.
authors.forename: F
authors.initials: F
authors.lastname: Evertsen
authors.forename: J I
authors.initials: JI
authors.lastname: Medbø
authors.forename: E
authors.initials: E
authors.lastname: Jebens
authors.forename: K
authors.initials: K
authors.lastname: Nicolaysen
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D010101:Oxygen Consumption; D010809:Physical Fitness; D012865:Skiing / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase