Hypohydration effects on thermoregulation during moderate exercise in the cold.
Hyperosmotic hypovolemia impairs vasoconstriction during sedentary cold exposure. The purpose of this study was to determine whether hypohydration alters thermoregulation and cardiovascular responses to exercise in cold air. On four occasions, eight males [35.1 (2.7) years, 175.5 (3.1) cm, 73.3 (2.6) kg, 57.2 (2.6) ml kg(-1) min(-1) maximal oxygen uptake (VO(2max)), 19.6 (2.4)% fat] walked, in t-shirt, shorts, and shoes, at 50% VO(2max), for 60 min in either a 4 degrees C (Cold) or a 25 degrees C (Temperate) environment in both hypohydrated state (HYPO, -4% body mass) and euhydrated state (EU). During exercise-cold stress, rectal temperature ( T(re)), mean weighted skin temperature, heart rate (HR), cardiac output (CO), and stroke volume (SV) were measured every 20 min. Mean weighted skin temperature values were not different between HYPO and EU but were lower ( P<0.05) in Cold versus Temperate trials. T(re) was not different ( P>0.05) between HYPO-Cold and EU-Cold. CO and SV were not different within hydration states and were not different between Cold and Temperate trials ( P<0.05). HR was not different between HYPO-Cold and EU-Cold. These data demonstrate that moderate intensity exercise in the cold while hypohydrated does not alter metabolic heat production, skin temperatures and heat loss, nor does it increase thermoregulatory and cardiovascular strain.
Kenefick
Robert W
RW
Department of Kinesiology, The University of New Hampshire, New Hampshire Hall, NH 03824, Durham, USA. RWK@hopper.unh.edu
Mahood
Nicholas V
NV
Hazzard
Melissa P
MP
Quinn
Timothy J
TJ
Castellani
John W
JW
D000328:Adult; D001833:Body Temperature Regulation / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology; D003080:Cold Temperature; D003681:Dehydration / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D012881:Skin Temperature / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology; D016138:Walking / Q000502:physiology