Interstitial and arterial-venous [K+] in human calf muscle during dynamic exercise: effect of ischaemia and relation to muscle pain.
Changes in the concentration of interstitial K+ surrounding skeletal muscle fibres ([K+]I) probably play some role in the regulation of cardiovascular adjustments to muscular activity, as well as in the aetiology of muscle pain and fatigue during high-intensity exercise. However, there is very little information on the response of [K+]I to exercise in human skeletal muscle. Five young healthy subjects performed plantar flexion exercise for four 5 min periods at increasing power outputs ( approximately 1-6 W) with 10 min intervening recovery periods, as well as for two 5 min periods with ischaemia at approximately 1 and approximately 3 W. Microdialysis probes were inserted into the gastrocnemius medialis muscle of the right leg to measure [K+]I, and K+ release from the plantar flexors during and after incremental exercise was calculated from plasma flow and arterial-venous differences for K+. Calf muscle pain was assessed using a visual analogue scale. On average, [K+]I was 4.4 mmol l(-1) at rest and increased during minutes 3-5 of incremental exercise by approximately 1-7 mmol l(-1) as a positive function of power output. K+ release also increased as a function of exercise intensity, although there was a progressive increase by approximately 1-6 mmol l-1 in the [K+] gradient between the interstitium and arterial-venous plasma. [K+]I was lower during ischaemic exercise than control exercise. In contrast to this effect of ischaemia on [K+]I, muscle pain was relatively higher during ischaemic exercise, which demonstrates that factors other than changes in [K+]I are responsible for ischaemic muscle pain. In conclusion, this study has demonstrated that during 5 min of dynamic exercise, [K+]I increases during the later period of exercise as a positive function of exercise intensity, ischaemia reduces [K+]I during rest and exercise, and the increase in [K+]I is not responsible for muscle pain during ischaemic exercise.
Green
S
S
Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark. s.green@qut.edu.au
Langberg
H
H
Skovgaard
D
D
Bulow
J
J
Kjaer
M
M
D000328:Adult; D001158:Arteries; D015444:Exercise / Q000502:physiology*; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D005528:Foot; D006801:Humans; D007511:Ischemia / Q000150:complications / Q000378:metabolism*; D007866:Leg; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism*; D009135:Muscular Diseases / Q000209:etiology / Q000378:metabolism*; D010146:Pain / Q000209:etiology / Q000378:metabolism; D011188:Potassium / Q000097:blood / Q000378:metabolism*; D012016:Reference Values; D014680:Veins
D011188:Potassium