Physiological and performance benefits of halftime cooling

doi:10.1016/S1440-2440(05)80020-9

Journal of Science and Medicine in Sport

Volume 8, Issue 1, March 2005, Pages 15-25

https://doi.org/10.1016/S1440-2440(05)80020-9 Get rights and content

This study examined the effect of a 10-min, halftime cooling application on physiological and psychological parameters known to affect performance. Fourteen volunteers (10 male, 4 female) completed two randomised trials 48 hr to 7 days apart. Trials consisted of a 1-hr cycling protocol: 30 min at 75% V̇O_2max followed by 10 min cooling (application of a cooling jacket) or passive recovery (control), and a second 30-min exercise bout consisting of 20 min at 75% V̇O_2max, immediately followed by a 10-min maximal effort, where work was measured as energy expended (kJ). Performance of the 10-min maximal intensity phase tended to improve (171.5±30.4 kJ vs 165.4±29.2 kJ, p= 0.087) following the cooling trial. Heart rate during the 5th min of the maximal effort, (183±9 beats.min⁻¹ vs 180±7 beats.min⁻¹, p= 0.024), blood lactate concentration at 6 min post-exercise (9.3±3.1 mmol·L⁻¹ vs 7.9±3.2 mmol·L^-1, p= 0.007), rating of perceived exertion at the 20th min post-halftime recovery (15±2 vs 16±2, p= 0.042), and subjective rating of feelings and emotions differed between the cooling and control conditions. Sweat loss, core and mean skin temperature and rating of thermal sensation failed to differ significantly between conditions. Halftime cooling tended to result in greater aerobic performance. Psychological assessment revealed a dramatic placebo effect from the cooling application confounding these results. Furthermore, the cooling intervention failed to induce any significant thermoregulatory effects.

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Cited by (33)

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This study aims to evaluate the effectiveness of personal cooling strategies (PCSs) in reducing human heat stress, and determine the appropriate cooling strategies for medical workers. A meta-analysis method is employed to summarize, analyze and compare the effects of various PCSs on human physiological and psychological responses as well as performance, and to provide solid suggestions for selecting the optimal PCS for medical workers. External body cooling strategies (EBCSs) are found to exert large benefits in improving human physiological and psychological responses as well as human performance, and is more effective than internal body cooling strategies (IBCSs). IBCSs showed moderate effect in reducing core temperature, which may be practical for medical workers in extremely high outdoor temperatures and could be applied before wearing PPE. Liquid cooling clothing (LCC) provides larger cooling benefits than other types of EBCSs, then followed by air-cooling clothing (ACC) and hybrid cooling clothing (HCC), and phase change cooling clothing (PCMC) and semiconductor cooling device (SCD) ranks the last. Considering their applications for medical workers, nonportable LCC and ACC with cooling devices placed aside are practical for medical workers working in indoors or around buildings with less body movement and fewer postures; whereas portable LCC using a backpack and ACC using air fans are suitable for most medical workers with large range movements working in various locations. When using ACC, an air filtration system should be used together to filter the ambient air. SCD in the form of cooling chairs is only applicable for sedentary medical work around buildings in high outdoor temperatures. PCMC is more preferable for medical workers who work for a relatively short time or could change the PCM packs during work. This review serves as a foundational reference source for the selection or construction of highly effective and practical PCSs to reduce heat stress of medical workers.
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Citation Excerpt :
Despite this, a small correlation between exercise time and the blunted rise in perceptual strain index was found, indicating that a slower increase in perceptual strain may extend the exercise time to fatigue. However, this perceptual benefit for performance enhancement following cooling may be attributed to a placebo effect (Hornery et al., 2005). The current findings indicated that exercise performance in HCV could be enhanced with the reduced heart rate drift over time and the blunted rise in physiological strain index.
While continuous cooling strategies may induce some ergonomic problems to occupational workers, cooling between work bouts may be an alternative for cooling them down in hot environments. The purpose of this study was to assess the effects of wearing a newly designed hybrid cooling vest (HCV) between two bouts of exercise. Inside a climatic chamber set at an air temperature of 37 °C and a relative humidity of 60%, twelve male participants underwent two bouts of intermittent exercise interspersed with a 30 min between-bout recovery session, during which HCV or a passive rest without any cooling (PAS) was administered. The results indicated that thermoregulatory, physiological, and perceptual strains were significantly lower in HCV than those in PAS during the recovery session (p≤0.022), which were accompanied with a large effect of cooling (Cohen's d=0.84–2.11). For the second exercise bout, the exercise time following HCV (22.13±12.27 min) was significantly longer than that following PAS (11.04±3.40 min, p=0.005, d=1.23) During this period, core temperature T_c was significantly lower by 0.14±0.0.15 °C in HCV than that in PAS. The heart rate drift over time was declined by 2±2 bpm min⁻¹ (p=0.001, d=1.00) and the rise in physiological strain index was reduced by 0.11±0.12 unit min⁻¹ (p=0.010, d=0.96) following the use of HCV. These findings suggested that using HCV could accelerate between-bout recovery and improve subsequent exercise performance by the enlarged body core temperature margin and blunted cardiovascular drift.
Meta-analysis of the effects of microclimate cooling systems on human performance under thermal stressful environments: Potential applications to occupational workers
2015, Journal of Thermal Biology
Citation Excerpt :
In addition to the physiological effects of MCSs, psychological responses are non-negligible. Previous studies indicated that psychological responses have a strong influence on human performance (Hornery et al., 2005; Lee et al., 2008). However, the findings of these studies were inconsistently reported.
This study aims to determine the appropriate microclimate cooling systems (MCSs) to reduce heat stress and improve human performance of occupational workers and their practicality in the occupational field. Meta-analysis was employed to summarize, analyze, and compare the effects of various MCSs on human performance with corresponding physiological and psychological responses, thereby providing solid suggestions for selecting suitable MCSs for occupational workers. Wearing MCSs significantly attenuated the increases in core temperature (−0.34 °C/h) and sweating rate (−0.30 L/h), and significantly improved human performance (+29.9%, effect size [EFS]=1.1) compared with no cooling condition (CON). Cold air-cooled garments (ACG-Cs; +106.2%, EFS=2.32) exhibited greater effects on improving human performance among various microclimate cooling garments (MCGs), followed by liquid cooling garments (LCGs; +68.1%, EFS=1.86) and hybrid cooling garment combining air and liquid cooling (HBCG-AL; +59.1%, EFS=3.38), natural air-cooled garments (ACG-Ns; +39.9%, EFS=1.12), and phase change material cooling garments (PCMCGs; +19.5%, EFS=1.2). Performance improvement was observed to be positively and linearly correlated to the differences of core temperature increase rate (r=0.65, p<0.01) and sweating rate (r=0.80, p<0.001) between MCSs and CON. Considering their application in industrial settings, ACG-Cs, LCGs, and HBCG-AL are practical for work, in which workers do not move frequently, whereas ACG-Ns and PCMCGs are more applicable for the majority of occupational workers. Further enhancement of the cooling efficiency of these two cooling strategies should be initiated.
Effect of cold water immersion after exercise in the heat on muscle function, body temperatures, and vessel diameter
2009, Journal of Science and Medicine in Sport
Citation Excerpt :
An increase in rectal temperature is associated with decreases in muscular performance through reductions in both the contractile function of muscle1 and central motor drive.2 Additionally, prolonged elevation of rectal temperature may decrease performance in subsequent exercise bouts.3–5 This has prompted practitioners to implement post-exercise cooling strategies through the use of cold water immersion (CWI) in an attempt to attenuate the deleterious effects of prolonged hyperthermia by rapidly lowering rectal temperature.
Cold water immersion (CWI) is a popular recovery modality, but actual physiological responses to CWI after exercise in the heat have not been well documented. The purpose of this study was to examine effects of 20-min CWI (14 °C) on neuromuscular function, rectal (T_re) and skin temperature (T_sk), and femoral venous diameter after exercise in the heat. Ten well-trained male cyclists completed two bouts of exercise consisting of 90-min cycling at a constant power output (216 ± 12 W) followed by a 16.1 km time trial (TT) in the heat (32 °C). Twenty-five minutes post-TT, participants were assigned to either CWI or control (CON) recovery conditions in a counterbalanced order. T_re and T_sk were recorded continuously, and maximal voluntary isometric contraction torque of the knee extensors (MVIC), MVIC with superimposed electrical stimulation (SMVIC), and femoral venous diameters were measured prior to exercise, 0, 45, and 90 min post-TT. T_re was significantly lower in CWI beginning 50 min post-TT compared with CON, and T_sk was significantly lower in CWI beginning 25 min post-TT compared with CON. Decreases in MVIC, and SMVIC torque after the TT were significantly greater for CWI compared with CON; differences persisted 90 min post-TT. Femoral vein diameter was approximately 9% smaller for CWI compared with CON at 45 min post-TT. These results suggest that CWI decreases T_re, but has a negative effect on neuromuscular function.
Meta-Analysis Review on the Effects of Personal Cooling Strategies in Reducing Thermal Stress of Medical Staff
2023, SSRN

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Original ResearchPhysiological and performance benefits of halftime cooling

Pre-cooling rowers can improve laboratory 2000m performance in hot-humid conditions

Improved running performance in hot humid conditions following whole body precooling

Med Sci Sports Exerc

Physiologic tolerance to uncompensable heat: intermittent exercise, field v's laboratory

Med Sci Sports Exerc

Investigation of the effects of the pre-cooling on the physiological responses to soccer-specific intermittent exercise

Euro J Appl Physiol

Effect of slightly lowered body temperatures on endurance performance in humans

J Appl Physiol

The influence of different external cooling methods on thermoregulatory responses before and after intense intermittent exercise in the heat

J Strength Cond Res

Perceptual and physiological responses during exercise in cool and cold water

Percept Mot Skills

Control of sweating in man after work-induced thermal load and symmetrically applied cooling

Euro J Appl Physiol

Thermoregulatory, cardiovascular, and muscular factors related to exercise after precooling

J Appl Physiol

Effect of a practical neck cooling device on core temperature during exercise

Med Sci Sports Exerc

Original Research
Physiological and performance benefits of halftime cooling