Exercising in the heat and its impact on our muscles & respiratory system

Hot weather training dubai

What impact does exercising in the heat have on our muscles and respiratory system? How does it compare to exercising in comfortable/cooler temperatures?

Dubai, UAE The process by which the body maintains body temperature is called thermoregulation which is primarily controlled by the hypothalamus in the brain. Elevated body temperature (hyperthermia) occurs when internal heat production exceeds our ability to lose that build of heat from our bodies to the environment. The hypothalamus tries to maintain a core temperature of about 36.1’C – 37.8’C. The core is made up of all our vital organs including the likes of the brain, gut, lungs (to name a few). We regulate this heat two ways: Stimulation of peripheral thermal receptors in the skin and secondly changes in blood temperature as it flows to the hypothalamus.

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At rest about two-thirds of the body’s normal heat loss occurs as a result of conduction/convection and radiation. As air temperature approaches skin temperature and exceeds 30.6’C evaporation becomes the primary means of heat dissipation. Training outdoors in summer, the heat is gained externally from the environment and this is further compounded by exercise. During exercise much of the internal heat is generated during muscular activity through energy metabolism. In cold environments shivering allows us to increase our metabolic rates 3-5 fold. During sustained vigorous exercise the metabolic rate can increase 20-25 times above resting level. This means we can be increasing the core temperature by about 1’C every 5-7mins.

Heat produced within working muscles is transferred to the body’s core and skin. During exercise, body heat is dissipated into the surrounding environment by radiation, convection, conduction and evaporation. If our environment temprature is greater than our core temperature then our ability to dissipate the heat is compromised.

Radiation: Is the loss of heat from a warmer object to a cooler object in the form of thermal energy without physical contact. In the UAE summer months 37’C+ the temperatures of the surrounding objects in the environment exceed our skin temperature. For example the sun or the roads and we therefore absorb the radiant heat

Conduction: Is the transfer of heat from a warm object to a cooler object such as absorbing heat through the turf or think of jumping into a cold river where heat loss from the body is rapid.

Convection: This will depend on conduction from the skin to water or air next to it. Its effectiveness is dependant on how fast the air or water next to the body is exchanged once it becomes warmer. Convection cools the body as air currents pass by while running or cycling.

Evaporation: Probably the most significant in the UAE hotter months. Off all our heat loss strategies this is the most effective way to cool the body. As core temperature rises during exercise, peripheral blood vessels dilate and sweat glands become stimulated to produce noticeable sweat. This can amount to a loss of 1.5-2 litres of body water in 1 hour. On dry hot days sweating can be responsible for more than 80% of heat loss. Sweating itself does not cool the body; It is the evaporation of the sweat that cools the body.

Three Things will affect this in our training

1.Exposure of more skin to the environment

2.The temp and relative humidity of the air

3.The convective air currents around the body

Physiological Changes > 10 days of Heat Exposure Training

  1. Decrease in heart rate and body temperature
  2. Increase in peripheral blood flow and plasma volume
  3. Sweating capacity doubles
  4. Sweat becomes more diluted (less salt minerals are lost)
  5. Sweat is distributed across the skins surface more evenly
  6. Earlier onset of sweat response at lower core temperature
  7. The increase in perspiration rate is maintained over a longer period of time

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Coach Phil! Call 04 518 5400

If our environment temprature is greater than our core temperature then our ability to dissipate the heat is compromised.
Phil Elder, Strength and Conditioning Coach and Lead Sport Scientist