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Just chill, so you can run faster

Nobody likes overheating while exercising, but your muscles and brain especially don’t. This trial tested two cooling methods that may improve aerobic running performance.

Study under review: Running performance in the heat is improved by similar magnitude with pre-exercise cold-water immersion and midexercise facial water spray

Introduction

Anyone who has exercised in hot weather has experienced how difficult[1] it is, compared to exercising in cooler temperatures. However, many people aren’t aware of the variety of methods that can be used to combat the heat. For example, 30 minutes of cooling before exercise via cold-water immersion[2] (CWI; meaning soaking in water at 24°C/75°F) has been shown to increase running time to exhaustion by 18%, and 60 minutes of CWI has been shown to improve 30-minute running time trial performance[3] by 4%. Though this sounds very appealing, it can be quite impractical to do in real life situations. Slightly more practical, but still not widely used, is ice slurry ingestion, which may lead to similar[2] results as CWI, or even better[4] results. Another approach to fighting the heat is to use cooling methods during exercise. Mid-cooling, also called percooling, includes using a neck-cooling collar[5], ingesting cold beverages[6], menthol mouth rinse[7], or the use of a facial water spray[8]. These methods have led to improvements in endurance performance of 5-7%.

The exact mechanisms for performance improvements remain to be determined, but several ideas have been proposed. By lowering the core body temperature[9] prior to exercise, pre-cooling allows greater work capacity by delaying the time it takes for the body to reach a critical temperature, which involuntarily reduces the exercise workload. It is also possible that the performance benefits are mitigated by changes in the central nervous system, as shown in Figure 1. The brain is given feedback that body temperatures are lower, permitting increased activation of skeletal muscle. This is particularly important for exercising in the heat, as it is thought[10] that the contribution of the central nervous system to fatigue might be greater in the heat than at moderate temperatures. It is likely that the responses to pre-cooling and mid-cooling are related, but more research is needed to differentiate the effects. Accordingly, this new study set up a head-to-head comparison of the physiological and performance responses of pre-cooling with CWI and mid-cooling by intermittent facial spray.

Figure 1: The role the CNS plays in exercise in the heat

Reference: Nybo et al. J Appl Physiol. 2001 Nov.

Exercise performance is impaired in the heat, but a variety of methods exist to mitigate this decline. Pre-cooling by soaking in cold water, and mid-exercise cooling via facial spray are two proven methods of improving exercise performance in the heat. This new study was designed to determine the differences between pre- and mid-cooling during exercise in the heat.

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