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Age Modulates Physiological Responses during Fan Use under Extreme Heat and Humidity

GAGNON, DANIEL1,2,3; ROMERO, STEVEN A.1; CRAMER, MATTHEW N.1; KOUDA, KEN1,4; POH, PAULA Y. S.1; NGO, HAI1; JAY, OLLIE5; CRANDALL, CRAIG G.1

Medicine & Science in Sports & Exercise: November 2017 - Volume 49 - Issue 11 - p 2333–2342
doi: 10.1249/MSS.0000000000001348
Applied Sciences

Purpose: We examined the effect of electric fan use on cardiovascular and thermoregulatory responses of nine young (26 ± 3 yr) and nine aged (68 ± 4 yr) adults exposed to extreme heat and humidity.

Methods: While resting at a temperature of 42°C, relative humidity increased from 30% to 70% in 2% increments every 5 min. On randomized days, the protocol was repeated without or with fan use. HR, core (Tcore) and mean skin (Tsk) temperatures were measured continuously. Whole-body sweat loss was measured from changes in nude body weight. Other measures of cardiovascular (cardiac output), thermoregulatory (local cutaneous and forearm vascular conductance, local sweat rate), and perceptual (thermal and thirst sensations) responses were also examined.

Results: When averaged over the entire protocol, fan use resulted in a small reduction of HR (−2 bpm, 95% confidence interval [CI], −8 to 3), and slightly greater Tcore (+0.05°C; 95% CI, −0.13 to 0.23) and Tsk (+0.03°C; 95% CI, −0.36 to 0.42) in young adults. In contrast, fan use resulted in greater HR (+5 bpm; 95% CI, 0–10), Tcore (+0.20°C; 95% CI, 0.00–0.41), and Tsk (+0.47°C; 95% CI, 0.18–0.76) in aged adults. A greater whole-body sweat loss during fan use was observed in young (+0.2 kg; 95% CI, −0.2 to 0.6) but not aged (0.0 kg; 95% CI, −0.2 to 0.2) adults. Greater local sweat rate and cutaneous vascular conductance were observed with fan use in aged adults. Other measures of cardiovascular, thermoregulatory, and perceptual responses were unaffected by fan use in both groups.

Conclusions: During extreme heat and humidity, fan use elevates physiological strain in aged, but not young, adults.

1Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX; 2Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute Research Centre, Montréal, QC, CANADA; 3Department of Pharmacology and Physiology, Faculty of Medicine, University of Montreal, Montreal, QC, CANADA; 4Wakayama Medical University, Wakayama, JAPAN; and 5Faculty of Health Sciences, University of Sydney, Lidcombe, AUSTRALIA

Address for correspondence: Craig G. Crandall, Ph.D., Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Ave, Dallas, TX 75231; E-mail: craigcrandall@texashealth.org.

Submitted for publication February 2017.

Accepted for publication June 2017.

© 2017 American College of Sports Medicine