Author/Editor		Anderson, GS; Meneilly, GS; Mekjavić, Igor B
Title		Passive temperature lability in the elderly
Type		članek
Source		Eur J Appl Physiol Occup Physiol
Vol. and No.		Letnik 73, št. 3-4
Publication year		1996
Volume		str. 278-86
Language		eng
Abstract		Thermoregulatory responses of nine healthy elderly Šseven men and two women; mean age (SD) 73.9 (4.8) yearsĆ were compared to those of nine young adult men Š26.6 (5.2) yearsĆ. They exercised on a cycle ergometer for 20 min at an intensity inducing a heart rate equivalent to 65% of their predicted maximum, and were thereafter immersed in 28 degrees C water. The exercise was conducted to elevate tympanic temperature (Tty) and initiate a steady rate of sweating. The post-exercise immersion period induced gradual cooling of Tty, and changes in Tty relative to resting levels (delta Tty) at which sweating abated and shivering commenced were defined as the delta Tty thresholds for the cessation of sweating (Tsw) and onset of shivering (Tsh), respectively. In addition to Tty, oxygen uptake (VO2; l.min-1), sweating rate (g.m-2.min-1), and forehead skin blood perfusion were also measured during the trials. The mean (SD) Tsw occurred at a significantly (P < 0.005) higher delta Tty Š0.48 (0.18) degrees CĆ in the elderly than in the young adults Š0.21 (0.06) degrees CĆ, while the Tsh occurred at significantly (P < 0.005) lower delta Tty in the elderly Š-0.64 (0.34) degrees CĆ than in young adults Š-0.22 (0.10) degrees CĆ. Decreases in delta Tty below the shivering threshold were met with a significantly (P < 0.01) reduced VO2. The range of temperature lability between Tsw and Tsh, defined as the null-zone, was significantly greater in the elderly Š1.12 (0.39) degrees CĆ than in the young adults Š0.43 (0.12) degrees CĆ, and the slope of the vasoconstrictor response in the null-zone was significantly (P < 0.001) lower in the elderly subjects. The present study demonstrates a greater passive core temperature lability in older individuals, since the effector responses of sweating and shivering were initiated at higher and lower levels of Tty, respectively. (Abstract truncated at 2000 characters).
Descriptors		AGING BODY TEMPERATURE REGULATION AGED BICYCLING BODY TEMPERATURE COLD EXERCISE HEART RATE OXYGEN CONSUMPTION SHIVERING SWEATING