Summer is almost here in Ohio. Or, at least, it already feels like it’s here. It’s getting hot. The fans are blowing and the garages are open to let the beautiful soon-to-be-summer sunshine in, but your first thought after walking into your non-air conditioned gym is how miserable your training is going to feel in the heat.
To those of you who may have approached me already to share how hot it is in the gym, you may recall my adamant answer of, “You’ll be all right!” At that answer, you may have thought of me as a psycho, or a jerk that is simply ignoring your heat concern, but now I’m here to share with you the reason behind my answer:
There are benefits to training in the heat!
One of the most phenomenal abilities of the human body is its ability to adapt to external stressors, including the temperature of the environment. This adaptation is called acclimatization, which refers to being exposed to the natural environment. It is not to be confused with acclimation, for that type of adaptation requires exposure to an artificial environment to create a natural response (e.g., altitude chamber or tanning beds).
Similar to resistance training, safe and effective acclimatization to heat occurs when the amount of heat exposure gradually increases over time. Acclimatization to heat allows for an increase in performance while in the heat. The following is an outline of what adaptations occur to the body during heat acclimatization:
Days 1-5 of heat exposure:
An expansion of plasma blood volume. This increase creates a greater fluid reservoir for sweat production, which helps to retain central blood volume during continuous sweating. Body temperature does not rise as quickly, which prevents a reduction in heat tolerance.
A reduced heart rate at the trained exercise intensity. With the central blood volume being retained, blood circulation remains constant, and blood flow between the capillary beds and the active musculature is not compromised as there is no lack in blood availability. Similar to aerobic activities, an improvement in cardiovascular efficiency can be seen, for the heart does not need to work harder in order to maintain adequate blood flow.
Days 5-8 of heat exposure:
An increased sweat rate. The greater the amount of sweat, the greater the body’s ability to evaporate heat, which helps to protect from hyperthermia.
A quicker response for the onset of sweat. When the body begins to sweat at lower elevations of body temperature, thermal balance can be achieved sooner.
More dilute sweat. If you’ve ever noticed your skin feeling salty after exercise, it is because sodium chloride (NaCl) gets released along with water through the sweat glands. NaCl is needed for the maintenance of extracellular fluid volume (i.e., hydration). Training in the heat allows the body to better conserve NaCl while still increasing sweat production. The less NaCl excreted in sweat and in urine, the more prolonged the hydration.
By day 14 of heat exposure, most of the changes caused by heat acclimatization are complete. These changes include a lower core temperature at the onset of sweating; an increase in the use of radiation and convection as additional mechanisms to evaporation for heat loss; an overall increase in plasma volume; reductions in heart rate (at specific workloads), core temperature, and skin temperature; a decrease in oxygen consumption (at specific workloads); and an improvement in exercise economy (i.e., the amount of exercise performed per one unit of oxygen consumed).
It is important to note, however, that adaptations to heat are specific, similar to how adaptations to weight training are specific. If you are training in an environment that is primarily hot and humid, then the benefits to heat acclimatization will only be experienced in hot, humid environments. If you are training in an environment that is primarily hot and dry, then the benefits will only be experienced in dry heat. (If you are training at The Spot Athletics where we experience both types of heat on any given day, then you are getting the best of both worlds).
Although these benefits are great, you still must be cognizant of the dangers of training in the heat when you do not properly prepare. Like I previously stated, these benefits to heat acclimatization occur gradually; and, even with the benefits, heat will still cause a significant impact on performance and body regulation due to its natural effect of increasing the temperature. Keep yourself safe while training by choosing clothing that allows for sweat to dissipate, and having plenty of fluids on-hand to replace the fluid that was lost.
During exercise, metabolism plays the largest role in increasing body temperature, while evaporation via sweating is the main method for decreasing body temperature. As we move, our body is constantly working to maintain a thermal balance, where the amount of heat produced is equal to the amount of heat lost. Thermal balance is not only affected by the temperature of the environment, but also by the clothes that we wear. If we do not wear clothing that allows sweat to dissipate through it, then the partial pressure of water in the body increases. This increase consequently decreases the evaporation of sweat due to the water being unable to break through the skin, which leads to the risk of rising skin and internal temperatures. The type of clothing worn for training does impact your ability to perform, so it is important that you consider what to wear for hot training days.
Water is the greatest regulator of temperature in the body. The amount of body water decreases during exercise as sweat increases, and it has been found that fluid loss equal to a reduction in 1-2% of body weight causes a decline in performance. Within your body’s water is NaCl, which is an electrolyte that works to maintain the body’s energy, and plays a major role in neural transmission. Without properly functioning neural pathways, the brain would not be able to send signals to muscles for contraction, which includes your heart muscle. Although it is difficult to accurately measure fluid loss during exercise, you must always have water (at the very least) and some form of electrolyte to replace fluid loss and maintain hydration. Typical recommended consumption of fluids following exercise is 16-20 fl oz. (2-2.5 cups) of fluid per pound of body weight lost.
As you continue to train in your non-air conditioned gym, you will notice that tolerating the heat becomes easier. The wall of heat that hits you as soon as you open the door into the facility won’t hit you as hard as it used to. You may tell yourself that it is because it isn’t so bad outside, but it is actually because your body has become adapted to the heat. So, with all of that being said, if you were to remember JUST ONE THING from this blog post…
“You will be alright!”
Fleck, SJ, and Kraemer, W. Designing Resistance Training Programs. 4th ed. Champaign, IL: Human Kinetics, 2014.