Potassium kinetics in human muscle interstitium during repeated intense exercise in relation to fatigue

Magni Mohr, Nikolai Baastrup Nordsborg, Jens Jung Nielsen, Lasse Danneman Pedersen, Christian Fischer, Peter Krustrup, Jens Bangsbo

Research output: Contribution to journalJournal articleResearchpeer-review


Accumulation of K+ in skeletal muscle interstitium during intense exercise has been suggested to cause fatigue in humans. The present study examined interstitial K+ kinetics and fatigue during repeated, intense, exhaustive exercise in human skeletal muscle. Ten subjects performed three repeated, intense (61.6+/-4.1 W; mean+/-SEM), one-legged knee extension exercise bouts (EX1, EX2 and EX3) to exhaustion separated by 10-min recovery periods. Interstitial [K+] ([K+]interst) in the vastus lateralis muscle were determined using microdialysis. Time-to-fatigue decreased progressively (P<0.05) during the protocol (5.1+/-0.4, 4.2+/-0.3 and 3.2+/-0.2 min for EX1, EX2 and EX3 respectively). Prior to these bouts, [K+]interst was 4.1+/-0.2, 4.8+/-0.2 and 5.2+/-0.2 mM, respectively. During the initial 1.5 min of exercise the accumulation rate of interstitial K+ was 85% greater (P<0.05) in EX1 than in EX3. At exhaustion [K+]interst was 11.4+/-0.8 mM in EX1, which was not different from that in EX2 (10.4+/-0.8 mM), but higher (P<0.05) than in EX3 (9.1+/-0.3 mM). The study demonstrated that the rate of accumulation of K+ in the muscle interstitium declines during intense repetitive exercise. Furthermore, whilst [K+]interst at exhaustion reached levels high enough to impair performance, the concentration decreased with repeated exercise, suggesting that accumulation of interstitial K+ per se does not cause fatigue when intense exercise is repeated.

Original languageEnglish
JournalPflügers Archiv - European Journal of Physiology
Issue number4
Pages (from-to)452-6
Publication statusPublished - 2004


  • Adult
  • Anaerobic Threshold
  • Glycogen
  • Humans
  • Hydrogen-Ion Concentration
  • Lactic Acid
  • Leg
  • Male
  • Muscle Fatigue
  • Muscle, Skeletal
  • Physical Endurance
  • Potassium
  • Sarcolemma
  • Journal Article
  • Research Support, Non-U.S. Gov't


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