According to Powers & Howley (2018) there are two responses, which are called behavior adaptations that our bodies go through in hot and cold environments. The first behavioral adaptation is when our blood vessels constrict in cold weather and vasodilate when the weather is warm to maintain proper body temperature. In addition, when our bodies are warm and the muscles at the surface of our skin vasodilate, we sweat in response to keeping our bodies cool.
Let’s look into what an athlete can do in order to perform at high levels in extreme heat environments. Understanding heat injuries or what scientists call, hyperthermia, can be dangerous and life-threatening which includes the following that need to be taken into consideration: exercise-induced muscle cramps, heat syncope, heat exhaustion and heat stroke (Powers & Howley, 2018).
We do not wish to get to the point of any of the following progressive injuries, but it is important to understand the signs and symptoms of each before we train:
Exercise-induced Muscle Cramps- “Sudden involuntary muscle contractions during or after exercise” (Powers & Howley, 2018). Immediate care includes rest, ice, massage, passive stretching and rehydration (Powers & Howley, 2018).
Heat Syncope- “Orthostatic dizziness attributed to dehydration, hypotension, venus pooling” (Powers & Howley, 2018). Some of the symptoms include brief episodes of fainting associated with dizziness and tunnel vision. Immediate care includes moving to a cool and shady area while rehydrating (Powers & Howley, 2018).
Heat Exhaustion- Excessive fatigue, fainting, confusion or disorientation (Powers & Howley, 2018). Immediate care recommends moving to a shaded and cool area while removing excess clothing, ice, rehydrate and refer to a physician (Powers & Howley, 2018).
Heat Stroke- High body temperature with disorientation, confusion and a rectal temperature of more than 40.5 degrees celcius (Powers & Howley, 2018). Removing excess clothing while lowering core temperature in a tub of ice water. Transfer to medical facility (Powers & Howley, 2018).
Exposing athletes with this information is important so that they understand the dangers of training in the heat as well as the importance of gradual acclimation. That acclimation has pieces that need to be understood:
1. Expose as much skin as possible to help evaporation of sweat as well as clothing that helps regulate heat well (Powers & Howley, 2018).
2. Exercise in heat for 10-14 days at two different intensities: low intensity (<50% VO2 max) and long duration or moderate intensity (75% VO2 max) and short duration (30-35 min.) so that an individual can increase plasma volume, improve performance, decrease salt loss in sweat and lower body temperature in response (Powers & Howley, 2018).
Bradley et al. (2019) conducted a study which compared skills of American Football players after what is called “Precooling”. This “Precooling” strategy was 15-minutes of cold water immersion before 8 different football skills were tested. Of those skills, the only ones that were impacted were throwing accuracy and 40-yard dash time. All of the other skills were not impared and the study proved to be effective at keeping the athletes core temperatures lower during competition.
3. Hydration is key to preventing any form of heat illness and should be monitored by weighing before and after exercise because Powers & Howley (2018) noted that there can be as much as an 8% loss in body weight related to water loss in endurance athletes. Sweat rates increase linearly with exercise intensity and when it is hot, one can lose 2.8 liters per hour (Powers & Howley, 2018). Research suggests that 150% of weight loss should be replenished by fluid or 1.5 liters of fluid for every 1 kg of body weight lost (3 cups per pound lost). It is also important to note that water alone is not enough to replace, but electrolytes in the form of sodium, potassium, chloride, and magnesium need to be replenished. Fluid replacement 8-24 hours before exercise is sufficient amount of time to become fully hydrated and 2-4 hours before is also recommended until urine color is pale yellow (Powers & Howley, 2018). Proper hydration can be obtained by drinking 400 to 800 ml of fluid during this pre- workout/competition. It is also recommended that fluid should be consumed during competition breaks in many sports as well as electrolyte replacement especially for those engaging in activities longer that 45 minutes. To be specific on the amount, consuming 150 to 300 ml of fluid every 15 to 20 minutes during exercise should help your body stay well hydrated.
In addition, Amornpan et al. (2019) mentioned that cold shower immersion can promote thermal comfort sensation by facilitating a faster heart rate recovery after an extreme heat session. A cold shower or immersion can be a great way to reduce cardiac stress for athletes after a workout in a hot environment.
4. Stay within target heart rate zone while also monitoring throughout the workout (Powers & Howley, 2018).
The preparation plan for an athlete competing in an extreme heat environment would be exactly what research noted earlier- gradually acclimatize the athlete over the course of 10-14 days while monitoring heart rate, intensity of training, core temperature and hydration status before, during and after activity. This would make sense to why most professional teams fly their athletes into a new city at least 4-5 days before competition to get used to the climate before the game.
If the athlete is not properly fueled, acclimated to the environment, trained well enough for the specific endeaver or even wearing the right clothing, performance can greatly be compromised. All of the above protocol need to be coached with the athlete in the beginning of the training season or program.
References:
Amornpan, A., Chaunchaiyakul, R., Pitsamai, S., & Widjaja, W. (2019). Effect of cold shower on recovery from high intensity cycling in the heat. The Journal of Strength and Conditioning Research, 33(8), 2233-2240. https://doi.org/10.1519/JSC0000000000003017
Bradley, L. J., Miller, K. C., Wiese, B. W., & Novak, J. R. (2019). Precooling’s effect on american football skills. The Journal of Strength and Conditioning Research, 33(10), 2616-2621. https://doi.org/10.1519/JSC0000000000003330
Powers, S. K., & Howley, E. T. (2018). Exercise physiology: Theory and application to fitness and performance (10th ed.). McGraw-Hill Education