Reduced volume and increased training intensity elevate muscle Na+-K+ pump alpha2-subunit expression as well as short- and long-term work capacity in humans.
The present study examined muscle adaptations and alterations in work capacity in endurance-trained runners as a result of a reduced amount of training combined with speed endurance training. For a 6- to 9-wk period, 17 runners were assigned to either a speed endurance group with a 25% reduction in the amount of training but including speed endurance training consisting of six to twelve 30-s sprint runs 3-4 times/wk (SET group n = 12) or a control group (n = 5), which continued the endurance training ( approximately 55 km/wk). For the SET group, the expression of the muscle Na(+)-K(+) pump alpha(2)-subunit was 68% higher (P < 0.05) and the plasma K(+) level was reduced (P < 0.05) during repeated intense running after 9 wk. Performance in a 30-s sprint test and the first of the supramaximal exhaustive runs was improved (P < 0.05) by 7% and 36%, respectively, after the speed endurance training period. In the SET group, maximal O(2) uptake was unaltered, but the 3-km (3,000-m) time was reduced (P < 0.05) from 10.4 +/- 0.1 to 10.1 +/- 0.1 min and the 10-km (10,000-m) time was improved from 37.3 +/- 0.4 to 36.3 +/- 0.4 min (means +/- SE). Muscle protein expression and performance remained unaltered in the control group. The present data suggest that both short- and long-term exercise performances can be improved with a reduction in training volume if speed endurance training is performed and that the Na(+)-K(+) pump plays a role in the control of K(+) homeostasis and in the development of fatigue during repeated high-intensity exercise.
Bangsbo
Jens
J
Department of Exercise and Sport Sciences, Section of Human Physiology, Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark. jbangsbo@aki.ku.dk
Gunnarsson
Thomas P
TP
Wendell
Jesper
J
Nybo
Lars
L
Thomassen
Martin
M
D000328:Adult; D000704:Analysis of Variance; D054874:Athletic Performance / Q000502:physiology; D015153:Blotting, Western; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003402:Creatine Kinase / Q000378:metabolism; D057075:Enzyme Assays; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D025203:Phosphofructokinase-1, Muscle Type / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011188:Potassium / Q000097:blood; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D064506:Solute Carrier Family 12, Member 2
C578877:SLC12A2 protein, human; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D019344:Lactic Acid; D002950:Citrate (si)-Synthase; D025203:Phosphofructokinase-1, Muscle Type; D003402:Creatine Kinase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium