Precooling and percooling (cooling during exercise) both improve performance in the heat: a meta-analytical review

Abstract

Background Exercise increases core body temperature (Tc), which is necessary to optimise physiological processes. However, excessive increase in Tc may impair performance and places participants at risk for the development of heat-related illnesses. Cooling is an effective strategy to attenuate the increase in Tc. This meta-analysis compares the effects of cooling before ( precooling) and during exercise ( percooling) on performance and physiological outcomes. Methods A computerised literature search, citation tracking and hand search were performed up to May 2013. 28 studies met the inclusion criteria, which were trials that examined the effects of cooling strategies on exercise performance in men, while exercise was performed in the heat (>30°C). 20 studies used precooling, while 8 studies used percooling. Results The overall effect of precooling and percooling interventions on exercise performance was +6.7±0.9% (effect size (ES)=0.43). We found a comparable effect (p=0.82) of precooling (+5.7±1.0% (ES=0.44)) and percooling (+9.9±1.9% (ES=0.40)) to improve exercise performance. A lower finishing Tc was found in precooling (38.9°C) compared with control condition (39.1°C, p=0.03), while Tc was comparable between conditions in percooling studies. No correlation between Tc and performance was found. We found significant differences between cooling strategies, with a combination of multiple techniques being most effective for precooling (p<0.01) and ice vest for percooling (p=0.02). Conclusions Cooling can significantly improve exercise performance in the heat. We found a comparable ES for precooling and percooling on exercise performance, while the type of cooling technique importantly impacts the effects. Precooling lowered the finishing core temperature, while there was no correlation between Tc and performance.

Ischaemic preconditioning does not alter the determinants of endurance running performance in the heat

“…However, it should be acknowledged that modest changes in T CORE have the potential to modify effector thresholds such as vasomotor and sudomotor sensitivity or sweat rate (Kondo et al 2009), however this effect may necessitate sweating to have commenced, which is unlikely during IP at rest, and may explain why neither T SKIN nor sweat rate subsequently differed. Whilst the observed reduction in T CORE may be considered small in comparison to that following precooling techniques (Bongers et al 2015;Tyler et al 2015), future research may also consider how this could complement a cooling strategy prior to competing in the heat. Moreover, future research should investigate changes in whole-body blood flow in order to understand the observed change in T CORE , that appears to be independent of changes in both muscle and skin temperatures.…”

Body-Cooling Paradigm in Sport: Maximizing Safety and Performance During Competition

“…24 Wearing cooling vests during exercise has shown the greatest improvement in exercise performance (20.4%), 79 whereas other evidence shows that ingesting cold water improves exercise performance by 12.4%. 80 Although cooling during exercise has shown improvements in performance, difficulties will arise when attempting to implement 1 modality across all sports due to the individual nature of each sport.…”

“…The improvement in performance from precooling focuses on the premise that lowering body temperature below its set point before exercise allows athletes to exercise at a higher intensity during exercise as they are afforded a greater temperature gradient before performance is adversely affected. 51,72,73 A recent meta-analytical review 24 found that precooling improved exercise performance by a factor of 5.7% overall, with mixed cooling methods (ie, CWI and cooling vests) providing the largest improvement in exercise performance (7.3%) Cooling postexercise has also been investigated in that cooling the body postexercise allows athletes to recover more quickly and thus have the potential to improve their performance in subsequent competition. 11,13 It is postulated that high internal thermal loads, often seen after intense exercise in the heat, result in the degradation of exercise performance and lengthen the time for the body to recover.…”

“…While cold drinks and cool packs have shown the largest improvements in performance when examining the influence of the modality itself, 37 it is suggested that using multiple forms of cooling may provide a greater benefit for performance. 24 The timing of body cooling has also been well investigated, particularly with cooling before exercise. The improvement in performance from precooling focuses on the premise that lowering body temperature below its set point before exercise allows athletes to exercise at a higher intensity during exercise as they are afforded a greater temperature gradient before performance is adversely affected.…”

“…22,23 Evidence also supports CWI as an effective modality to enhance performance when used before exercise and postexercise. 13,24 Reducing body temperature before competition permits athletes to exercise at a higher intensity by increasing heat-storage capacity, which can improve performance. Reducing body temperature quickly after competition allows for improved recovery, thus providing potential performance enhancements for subsequent bouts of exercise.…”