Potassium loss from skeletal muscle during exercise in man: a radioisotope study.

Journal article

Muscle potassium (K+) content decreases during exercise. Previous studies, in humans, have used measurements of arteriovenous plasma potassium concentration differences (AV delta[K+]) and/or muscle biopsy to measure the loss of muscle K+ during exercise. In the current study a non-invasive method was developed to measure skeletal muscle K+ before and after exercise, using an isotope of K+, potassium-43 (43K+). Twelve subjects performed single-leg extension exercise for 2 h at 50% of their maximum predicted heart rate. The level of radioactivity from the quadriceps femoris was determined before exercise and during two periods post-exercise. After correction for counts arising outside the exercised muscle, we estimate a decrease in muscle K+ content of 3.2 +/- 1.55% (mean +/- S.E.M.) following exercise. The muscle K+ was not restored following 75 min of recovery. The decrease in muscle K+ following exercise in our study is considerably less than that suggested by previous studies using AV delta[K+] measurements but not so dissimilar from results obtained using muscle biopsy. We conclude that a small but significant loss of K+ occurs following prolonged dynamic exercise, and that complete recovery of muscle K+ is slow.

Authors: Qayyum, MS; Freemantle, C; Carey, C; Page, B; Soper, N

• Publication status: Published
• Journal: Experimental physiology
• Volume: 78
• Issue: 5
• Pages: 639-648
• Publication date: 1993-09-01
• EISSN: 1469-445X
• ISSN: 0958-0670
• Language: English
• Keywords: Muscles; Exercise; Humans; Heart Rate; Male; Potassium; Potassium Radioisotopes; Adult; Physical Exertion