Human temperature regulation during cycling with moderate leg ischaemia |
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Authors: | Alan Kacin Petra Golja Ola Eiken Michael J. Tipton Jurij Gorjanc Igor B. Mekjavic |
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Affiliation: | (1) Department of Automation, Biocybernetics and Robotics, Institute Jozef Stefan, Jamova 39, 1000 Ljubljana, Slovenia;(2) Department of Sports and Exercise Science, Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, Portsmouth, UK;(3) Department of Physiotherapy, University of Ljubljana, Poljanska 26a, 1000 Ljubljana, Slovenia;(4) Nova Gorica Polytechnic, Vipavska 13, 5000 Nova Gorica, Slovenia;(5) Swedish Defence Research Agency, Karolinska Institutet, Berzelius v. 13, 17177 Stockholm, Sweden;(6) Slovenj Gradec General Hospital, Slovenj Gradec, Slovenia |
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Abstract: | The effect of graded ischaemia in the legs on the regulation of body temperature during steady-state exercise was investigated in seven healthy males. It was hypothesised that graded ischaemia in the working muscles increases heat storage within the muscles, which in turn potentiates sweat secretion during exercise. Blood perfusion in the working muscles was reduced by applying a supra-atmospheric pressure (+6.6 kPa) around the legs, which reduced maximal working capacity by 29%. Each subject conducted three separate test trials comprising 30 min of steady-state cycling in a supine position. Exercise with unrestricted blood flow (Control trial) was compared to ischaemic exercise conducted at an identical relative work rate (Relative trial), as well as at an identical absolute work rate (Absolute trial); the latter corresponding to a 20% increase in relative workload. The average (SD) increases in both the rectal and oesophageal temperatures during steady-state cycling was 0.3 (0.2)°C and did not significantly differ between the three trials. The increase in muscle temperature was similar in the Control (2.7 (0.3)°C) and Absolute (2.4 (0.7)°C) trials, but was substantially lower (P<0.01) in the Relative trial (1.4 (0.8)°C). Ischaemia potentiated (P<0.01) sweating on the forehead in the Absolute trial (24.2 (7.3) g m–2 min–1) compared to the Control trial (13.4 (6.2) g m–2 min–1), concomitant with an attenuated (P<0.05) vasodilatation in the skin during exercise. It is concluded that graded ischaemia in working muscles potentiates the exercise sweating response and attenuates vasodilatation in the skin initiated by increased core temperature, effects which may be attributed to an augmented muscle metaboreflex. |
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Keywords: | Thermoregulation Dynamic exercise Ischaemia Muscle temperature Sweating Skin vasomotor tone |
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