Reduction of Physiological Strain Under a Hot and Humid Environment by a Hybrid Cooling Vest

Abstract

Cooling treatment is regarded as one of good practices to provide safe training conditions to athletic trainers in the hot environment. The present study aimed to investigate whether wearing a commercial lightweight and portable hybrid cooling vest that combines air ventilation fans with frozen gel packs was an effective means to reduce participants' body heat strain. In this within-subject repeated measures study, 10 male volunteers participated in two heat-stress trials (one with the cooling vest - COOL condition, and another without - CON condition, in a randomized order) inside a climatic chamber with a controlled ambient temperature 33 °C and relative humidity (RH) 75% on an experimental day. Each trial included a progressively incremental running test, followed by a 40 min post-exercise recovery. Core temperature (Tc), heart rate (HR), sweat rate, rating of perceived exertion (RPE), exercise duration, running distance, power output, and sweat rate were measured. When comparing the two conditions, a non-statistically significant moderate cooling effect in rate of increase in Tc (0.03±0.02 °C/min for COOL vs. 0.04±0.02 °C/min for CON, p=0.054, d=0.57), HR (3±1 bpm/min for COOL vs. 4±1 bpm/min for CON, p=0.229, d=0.40), and physiological strain index (PSI) (0.20±0.06 unit/min for COOL vs. 0.23±0.06 unit/min for CON, p=0.072, d=0.50) was found in the COOL condition during exercise. A non-statistically significant (p>0.05) trivial cooling effect (d<0.2) was observed between the COOL and CON conditions for measures of exercise duration, running distance, power output, sweat rate and RPE. It is concluded that the use of the hybrid cooling vest achieved a moderate cooling effect in lowering the rate of increase in physiological strain without impeding the performance of progressively incremental exercise in the heat.

Effect of previous lowering of skin temperature on the time of safe exposure to a hot environment: a case study

“…In cases where it is necessary, vest cooling is preferred in rescue operations, and in sport, cooling of the body or body part before the start. The effectiveness of these methods is generally confirmed in the literature; however, it is noted that extending the time of activity in heat or briefly increasing the thermoregulatory capacity of the body should be considered in terms of specific environmental conditions and human activity [21,22].…”

“…Current research focuses on ways to reduce active heat accumulation in extreme conditions, which would create opportunities to extend the safe activity time. These studies are conducted in many directions [11][12][13][14][15][16][17][18][19][20][21][22]. Various cooling methods aimed at reducing the human heat load have been studied.…”

“…The heart rate responses during the recovery period and a second work bout were significantly lower for hand/forearm immersion. The lowering of the temperature of the bodies and limbs was also used in sport to achieve higher fitness during competitions [21,22].…”

Cooling During Exercise May Induce Benefits Linked to Improved Brain Perfusion

“…This vest may procure more comfort during exercise and recovery than an ice vest, which has been known to cause discomfort and produce severe cooling with a risk of erythema [39]. Hence, a ventilated vest could have a beneficial effect on the reduction of physiological strain during exercise and post-exercise recovery [40] by increasing sweat evaporation and decreasing the levels of thermal and cardiovascular stress [41,42].…”

“…Cooling the skin was proposed to be a suitable solution to improve thermal sensations in participants [1]. The cooling vest used in the present study consists of active cooling (ventilation) known to stimulate heat loss and provide a feeling of freshness [40]. Additionally, the chest and back are 2 large body areas sensitive to cold.…”