title: Potassium loss from skeletal muscle during exercise in man: a radioisotope study.
abstract: 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.affiliation: University Laboratory of Physiology, Oxford.
authors.forename: M S
authors.initials: MS
authors.lastname: Qayyum
authors.forename: C A
authors.initials: CA
authors.lastname: Freemantle
authors.forename: C J
authors.initials: CJ
authors.lastname: Carey
authors.forename: B C
authors.initials: BC
authors.lastname: Page
authors.forename: N
authors.initials: N
authors.lastname: Soper
authors.forename: D J
authors.initials: DJ
authors.lastname: Paterson
authors.forename: P A
authors.initials: PA
authors.lastname: Robbins
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D009132:Muscles / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology; D011188:Potassium / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D011197:Potassium Radioisotopes
chemical_list: D011197:Potassium Radioisotopes; D011188:Potassium