A Mixed-Method Approach of Pre-Cooling Enhances High-Intensity Running Performance in the Heat

Abstract

We investigated whether single or combined methods of pre-cooling could affect high-intensity exercise performance in a hot environment. Seven male athletes were subjected to four experimental conditions for 30 min in a randomised order. The four experimental conditions were: 1) wearing a vest cooled to a temperature of 4 ℃ (Vest), 2) consuming a beverage cooled to a temperature of 4 ℃ (Beverage), 3) simultaneous usage of vest and consumption of beverage (Mix), and 4) the control trial without pre-cooling (CON). Following those experimental conditions, they exercised at a speed of 80% VO₂max until exhaustion in the heat (38.1 ± 0.6 ℃, 55.3 ± 0.3% RH). Heart rate (HR), rectal temperature (T_core), skin temperature (T_skin), sweat loss (SL), urine specific gravity (USG), levels of sodium (Na⁺) and potassium (K⁺), rating of perceived exertion (RPE), thermal sensation (TS), and levels of blood lactic acid ([Bla]) were monitored. Performance was improved using the mixed pre-cooling strategy (648.43 ± 77.53 s, p = 0.016) compared to CON (509.14 ± 54.57 s). T_core after pre-cooling was not different (Mix: 37.01 ± 0.27 ℃, Vest: 37.19 ± 0.33 ℃, Beverage: 37.03 ± 0.35 ℃) in all cooling conditions compared to those of CON (37.31 ±0.29 ℃). A similar T_core values was achieved at exhaustion in all trials (from 38.10 ℃ to 39.00 ℃). No difference in the level of USG was observed between the conditions. Our findings suggest that pre-cooling with a combination of cold vest usage and cold fluid intake can improve performance in the heat.

Keywords: Cooling prior to exercise; external and internal cooling; high-intensity aerobic exercise; hyperthermia; thermoregulation.

Figure 1.

Flow-process diagram of the entire precooling research, which includes the procedure and measurements (n = 7). P; The 30-min precooling maneuvers include different interventions and one control. E; The exercise protocol would be terminated when the subject was exhausted. a. All date recorded within 5 min. b. Precooling protocols started. c. Precooling protocols terminated. d. Exercise protocol began.

Figure 2.

Time to exhaustion at 80% of VO₂max in a hot environment (38.1 ± 0.6 ℃, 55.3 ± 0.3 % relative humidity, mean ± S.D., n = 7). * p < 0.05 vs. CON

Figure 3.

Urine specific gravity (USG) change at the point of exercise exhaustion. Data are means ±SD, n = 7.