Passive temperature lability in the elderly |
| |
Authors: | G S Anderson G S Meneilly I B Mekjavic |
| |
Institution: | (1) School of Kinesiology, Simon Fraser University, V5A 1S6 Burnaby, British Columbia, Canada;(2) Faculty of Medicine, University of British Columbia, V6T 1Z3 Vancouver, British Columbia, Canada;(3) University College of the Fraser Valley, 33844 King Rd. RR 2, V2S 4N2 Abbotsford, British Columbia, Canada |
| |
Abstract: | Thermoregulatory responses of nine healthy elderly seven men and two women; mean age (SD) 73.9 (4.8) years] were compared
to those of nine young adult men 26.6 (5.2) years]. 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°C water. The exercise was conducted
to elevate tympanic temperature (T
ty) and initiate a steady rate of sweating. The post-exercise immersion period induced gradual cooling ofT
ty, and changes inT
ty relative to resting levels (ΔT
ty) at which sweating abated and shivering commenced were defined as the ΔT
ty thresholds for the cessation of sweating (T
sw) and onset of shivering (T
sh), respectively. In addition toT
ty, oxygen uptake (
; 1 · min−1), sweating rate (g · m−2 · min−1), and forehead skin blood perfusion were also measured during the trials. The mean (SD)T
sw occurred at a significantly (P <0.005) higher ΔT
ty 0.48 (0.18)°C] in the elderly than in the young adults 0.21(0.06)°C], while the Tsh occurred at significantly (P < 0.005) lower ΔT
ty in the elderly −0.64 (0.34)°C] than in young adults −0.22 (0.10)°C]. Decreases in ΔT
ty below the shivering threshold were met with a significantly (P <0.01) reduced
. The range of temperature lability between Ts, andT
sh, defined as the null-zone, was significantly greater in the elderly 1.12 (0.39)°C] than in the young adults 0.43 (0.12)°C],
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 ofT
ty, respectively. The magnitudes of the effector responses beyond the thresholds were also significantly reduced, suggesting
that the elderly may be more susceptible to hypo-/hyperthermia during periods of endogenous and/or exogenous thermal stress. |
| |
Keywords: | Temperature regulation Aging Sweating Perfusion Shivering Thermal comfort |
本文献已被 SpringerLink 等数据库收录! |
|