Effect of Work-to-Rest Cycles on Cardiovascular Strain and Maximal Oxygen Uptake during Heat Stress

Anne M. Mulholland (), Hillary A. Yoder and Jonathan E. Wingo
Additional contact information
Anne M. Mulholland: Department of Kinesiology, The University of Alabama, Tuscaloosa, AL 35487, USA
Hillary A. Yoder: Department of Kinesiology, The University of Alabama, Tuscaloosa, AL 35487, USA
Jonathan E. Wingo: Department of Kinesiology, The University of Alabama, Tuscaloosa, AL 35487, USA

IJERPH, 2023, vol. 20, issue 5, 1-13

Abstract: Cardiovascular drift—a progressive increase in heart rate (HR) and decrease in stroke volume (SV) during prolonged exercise—is exacerbated by heat stress and thermal strain, and often accompanied by a decrease in work capacity (indexed as maximal oxygen uptake [ V . O 2max ]). To attenuate physiological strain during work in the heat, use of work:rest ratios is recommended by the National Institute for Occupational Safety and Health. The purpose of this study was to test the hypothesis that during moderate work in hot conditions, utilizing the recommended 45:15 min work:rest ratio would result in cardiovascular drift ‘accumulating’ over consecutive work:rest cycles and accompanying decrements in V . O 2max . Eight people (5 women; (mean ± SD) age = 25 ± 5 y; body mass = 74.8 ± 11.6 kg; V . O 2max = 42.9 ± 5.6 mL·kg −1 ·min −1 ) performed 120 min of simulated moderate work (201–300 kcal·h −1 ) in hot conditions (indoor wet-bulb globe temperature = 29.0 ± 0.6 °C). Participants completed two 45:15 min work:rest cycles. Cardiovascular drift was evaluated at 15 and 45 min of each work bout; V . O 2max was measured after 120 min. On a separate day, V . O 2max was measured after 15 min under identical conditions for comparison before and after cardiovascular drift occurred. HR increased 16.7% (18 ± 9 beats·min −1 , p = 0.004) and SV decreased 16.9% (−12.3 ± 5.9 mL, p = 0.003) between 15 and 105 min, but V . O 2max was unaffected after 120 min ( p = 0.14). Core body temperature increased 0.5 ± 0.2 °C ( p = 0.006) over 2 h. Recommended work:rest ratios preserved work capacity but did not prevent the accumulation of cardiovascular and thermal strain.

Keywords: cardiovascular drift; occupational health and safety; work:rest ratios; work capacity (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2023
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

Downloads: (external link)
https://www.mdpi.com/1660-4601/20/5/4580/pdf (application/pdf)
https://www.mdpi.com/1660-4601/20/5/4580/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jijerp:v:20:y:2023:i:5:p:4580-:d:1087843

Access Statistics for this article

IJERPH is currently edited by Ms. Jenna Liu

More articles in IJERPH from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().