Exercising in the cold inhibits growth hormone secretion by reducing the rise in core body temperature.
OBJECTIVE
Ambient temperature alters exercise induced GH secretion. It is unknown whether temperature affects GH secretion at exercise intensities above the anaerobic threshold when other factors may override the relationship seen at lower intensities.


METHODS



METHODS
Cross-over study of ambient temperature on exercise induced GH in swimmers and rowers.


METHODS
St Thomas Hospital, London.


METHODS
Ten healthy men (age 21.7+/-0.8 yrs). Five swimmers and five rowers.


METHODS
Forty-minute exercise test at 105% of anaerobic threshold at room temperature (RT) and at 4 degrees C.


METHODS
Cutaneous and core body temperature. Serum GH concentration.


RESULTS
Cutaneous body temperature increased during exercise at RT but decreased in the cold. Although core temperature rose in both settings, the rise was greater at RT (p=0.021). GH increased at both temperatures but the onset was delayed by the cold. Peak GH tended to be higher at RT (17.4+/-3.6 microg/L vs. 9.5+/-1.5 microg/L, p=0.07). Total GH secretion was greater at RT (353.3+/-99.1 microg min/L) than 4 degrees C (128.3+/-21.0 microg min/L), p=0.038. Change in core temperature correlated with log peak GH (r=0.66, p=0.039) and log incremental GH (r=0.67, p=0.032) when exercising at 4 degrees C. There was no difference between swimmers and rowers.


CONCLUSIONS
Exercise at 4 degrees C reduces GH secretion during exercise at intensities above the anaerobic threshold. A change in core body temperature may be one mechanism by which exercise induces GH secretion. The difference in GH between swimmers and rowers during their respective events relates to the conditions under which they compete.
Wheldon
Adam
A
Department of Medicine, Guy's, King's and St Thomas' School of Medicine, King's College London, London SE1 7EH, UK.
Savine
Richard L
RL
Sönksen
Peter H
PH
Holt
Richard I G
RI
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology*; D003080:Cold Temperature; D015444:Exercise / Q000502:physiology*; D019382:Human Growth Hormone / Q000097:blood* / Q000378:metabolism; D006801:Humans; D008297:Male; D012881:Skin Temperature / Q000502:physiology*; D013177:Sports / Q000502:physiology
D019382:Human Growth Hormone