OBJECTIVE: To compare thermoregulatory responses of highly trained men who are tetraplegic during 40 min exercise at 65% VO2peak and 60 min immersion in 39 degrees C water. METHODS: Four physically trained men who are tetraplegic participated in three laboratory visits. The first visit involved familiarisation and then determination of VO2peak using open circuit spirometry during an incremental test to exhaustion with each man propelling his sport wheelchair on a motor driven treadmill. The order of second and third visits was randomly allocated. Visit 2 involved 40 min of exercise at 65% VO2peak propelling each man's sport wheelchair on treadmill. Visit 3 involved sitting immersed to nipple line in 39 degrees C water for 60 min. Venous blood was obtained pre, during and after each intervention and analyzed for haemoglobin, haematocrit and changes in plasma volume were calculated. Separated plasma was analyzed for noradrenalin and adrenalin (high performance liquid chromatography). Heart rate, rectal temperature, and sweat rate estimated from a sweat capsule placed on forehead (dew point hygrometry) were recorded throughout. RESULTS: VO2peak and HRmax of these subjects were 1.14 +/- 0.16 l/min and 99 +/- 4 b/min respectively. Heart rate preimmersion was 67 +/- 4 b/min rising to 75 +/- 4 b/min after 40 min and 87 +/- 3 b/min after 60 min immersion. Heart rate was 68 +/- 3 b/min pre-exercise rising to 91 +/- 5 b/min after 40 min exercise. Rectal temperature rose from 35.97 +/- 0.30 degrees C pre immersion to 37.32 +/- 0.51 degrees C after 60 min immersion, and from 36.42 +/- 0.20 degrees C pre-exercise to 36.67 +/- 0.19 degrees C after 40 min exercise. Haemoconcentration occurred during 40 min of exercise and haemodilution occurred throughout 60 min of water immersion. Three participants demonstrated no sweating on the forehead during immersion or exercise. One subject commenced sweating after 20 min exercise and after 5 min of immersion. CONCLUSION: Compared to exercise, immersion was associated with a lower heart rate, a lower plasma noradrenalin concentration and an expanded plasma volume. When considering exercise or warm water immersion as therapeutic modalities in men who are tetraplegic, attention should be paid to heat gain and changes in plasma volume.
Reprinted by permission from Spinal Cord, Macmillan Publishers Ltd.

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