J. Booth et al., Whole-body pre-cooling does not alter human muscle metabolism during sub-maximal exercise in the heat, EUR J A PHY, 84(6), 2001, pp. 587-590
Muscle metabolism was investigated in seven men during two 35 min cycling t
rials at 60% peak oxy gen uptake, at 35 degreesC and 50% relative humidity.
On one occasion, exercise was preceded by whole-body cooling achieved by i
mmersion in water during a reduction in temperature from 29 to 24 degreesC,
and, for the other trial, by immersion in water at a thermoneutral tempera
ture (control, 34.8 degreesC). Pre-cooling did not alter oxygen uptake duri
ng exercise (P > 0.05), whilst the change in cardiac frequency and body mas
s both tended to be lower following pre-cooling (0.05 < P < 0.10). When ave
raged over the exercise period, muscle and oesophageal temperatures after p
re-cooling were reduced by 1.5 and 0.6 degreesC respectively, compared with
control (P<0.05). Pre-cooling had a limited effect on muscle metabolism, w
ith no differences between the two conditions in muscle glycogen, triglycer
ide, adenosine triphosphate, creatine phosphate, creatine or lactate conten
ts at rest, or following exercise. These data indicate that whole-body pre-
cooling does not alter muscle metabolism during submaximal exercise in the
heat. It is more likely that thermoregulatory and cardiovascular strain are
reduced, through lower muscle and core temperatures.