title: 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.
abstract: 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 alpha1-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.
authors: Department of Exercise and Sport Sciences, Section of Human Physiology, Copenhagen Muscle Research Center, University of Copenhagen, Copenhagen, Denmark.
authors: F Marcello
authors: FM
authors: Iaia
authors: Martin
authors: M
authors: Thomassen
authors: Helle
authors: H
authors: Kolding
authors: Thomas
authors: T
authors: Gunnarsson
authors: Jesper
authors: J
authors: Wendell
authors: Thomas
authors: T
authors: Rostgaard
authors: Nikolai
authors: N
authors: Nordsborg
authors: Peter
authors: P
authors: Krustrup
authors: Lars
authors: L
authors: Nybo
authors: Ylva
authors: Y
authors: Hellsten
authors: Jens
authors: J
authors: Bangsbo
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D000693:Anaerobiosis / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002021:Buffers; D027682:Cation Transport Proteins / Q000096:biosynthesis*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*; D011188:Potassium / Q000097:blood; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis*; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis*
chemical_list: D002021:Buffers; D027682:Cation Transport Proteins; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D019344:Lactic Acid; C499076:ATP1A1 protein, human; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium