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F19U FREE COMMUNICATION/POSTER SKELETAL MUSCLE II

ACCUMULATION OF POTASSIUM IN MUSCLE INTERSTITIUM DURING EXHAUSTIVE EXERCISE IN HUMAN

Pedersen, L D.1; Mohr, M1; Nordsborg, N1; Nielsen, J J.1; Bangsbo, J1

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Medicine & Science in Sports & Exercise: May 2001 - Volume 33 - Issue 5 - p S263
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Accumulation of extracellular potassium in muscle has been suggested to cause fatigue during intense exercise. It is, however, unclear to what extent potassium rises in muscle interstitium during exercise. Thus, the aim of the present study was to examine the increase in interstitial potassium during exhaustive exercise and to evaluate the reproducibility of the microdialysis method. Six healthy male subjects had, on two separate occasions, six microdialysis probes inserted into m. vastus lateralis. On both occasions the subjects performed an exhaustive one-legged knee-extensor exercise bout (64.3 ± 3.1 (± SEM) W). Before and during the exercise dialysate from the microdialysis probes was frequently collected. Based on the dialysate potassium concentration and probe recovery the interstitial potassium concentration was determined. The time to exhaustion for the exercise performed on two separate days was 3.7 ± 0.4 and 4.1 ± 0.2 min, respectively. The interstitial potassium concentration was 4.4 ± 0.2 and 4.4 ± 0.3 mM before exercise, 8.7 ± 0.9 and 8.1 ± 0.5 mM after 1.25 min of exercise and 12.0 ± 1.2 and 11.7 ± 0.4 mM at the point of fatigue. Significant interprobe variations were observed within each subject with a mean range of 3.1 mM at the point of fatigue. The present study shows that interstitial potassium during short-term intense exhaustive exercise increases to levels that in vitro have been shown to reduce muscle force and indicates that potassium may cause muscular fatigue during intense exercise. In addition, the microdialysis technique seems to be a valid method to study potassium kinetics in human skeletal muscle during intense exercise.

©2001The American College of Sports Medicine