You already know or imagine it, if not let me tell you; hot weather and high temperatures affect your body’s ability to perform exercise. Many internal and external factors interact as your organism tries to adapt and respond to temperature changes (heat). Your training should consider this, as very dangerous heat-induced illness could compromise your health. How does it work? What happens when it fails? How does endurance sports performance suffers? Can we train for it? Keep reading.

Body response to heat: The body produces heat internally and also absorbs it from the environment. This physiological/metabolic exchange is called Thermoregulation and should result in a balanced internal temperature state, which is called homeostasis. Basically, your body needs to get efficient at getting heat away from its core for everything else to keep working effectively. The problems begin when it cannot get rid of it efficiently, during exercise or other long sun exposure activities, this is known as Hyperthermia. When the brain detects a sudden increment in temperature the hypothalamus activates its thermoregulation mechanisms.

The main 2 overheating defense mechanism are:

  • Skin vasolidation: the capillaries under your skin dilated and increase blood flow enabling heat elimination through radiation.
  •  Sweating (perspiration): by releasing sweat and its evaporation it helps cool down both your skin and internal temperatures.

Effects of hot weather on athletic performance/exercise:The main reason why optimum athletic performance is impaired in hot conditions is Cardiovascular strain. As heat infiltrates your body, the cardio system increases the minute cardiac output (Q) (more blood per pump), enhances skin blood perfusion (more blood to the skin and less to the muscles) and, deep epidermis blood perfusion which means less blood to the digestive and excretory systems, also an elevated heart rate (more pumps per minute). How does it affect athletic performance?

  • Brain functions that control muscles contraction are impaired; basically the brain doesn’t want the body to work hard to protect it from overheating.
  • Fatigued tolerance time is reduced. (you get tired earlier)
  • The effort decline rate is increased. (the process of getting tired is quicker)
  • Reduced power output (less muscle fiber recruitment)
  • Reduced VO2max capacity (maximum oxygen intake is less)

You can read a study on the topic HERE.

The good news is that the fitter we are the better we can perform in hot weather! By being better conditioned aerobically your body can prevent overheating issues through:

  • better heat dissipation and evaporation
  • better sweat response (starts earlier and more profuse)
  • lower initial core temperature
  • increased sensitivity to core temperature changes (can detect and trigger mechanisms earlier)
  • increased plasma volume
  • increased cardiac output

When thermoregulation fails: One of the problems today is the increasing number of participation in outdoor endurance and extreme events by people who are not well prepared. After prolonged exposition to sunlight and hot temperature 2 very bad things could happen, especially when your aerobic capacity is not sharp. As stated before, hyperthermia refers to an elevated body temperature. Any prolonged rise in the body’s temperature cause by more heat being produced than the one beinhyperthermia are Stopped sweat, hot and dry skin, tachycardia, tachypnea,confusion, faintness and/or unconsciousness. Read more HERE.


The 3 most common types of heat-induced illness are.

  • Heat syncope. Feelings of dizziness, weakness or light-headed, after sustained efforts in endurance events or long exposition to hot/humid conditions.
  • Heat stroke.  Your body thermoregulation mechanism fails at cooling it the core temperature reaches a very high number (104°F) that leads to failure of vital organs.
  •  Heat exhaustion. Your core temperature increases and the body start sweating and losing electrolytes at a rapid rate, leading to extreme dehydration that may result in a heat stroke.


Heat acclimatization: I was skeptical at first with the idea of acclimatizing, thinking it was a waste of time. Then in 2011 I hosted some athletes for the inaugural Ironman San Juan 70.3. I remember they came from Syracuse, NY training through a harsh winter and as I carry them around the island in my car they told me “You can keep the windows down, we need to get used to the heat’’. It was 90 degrees and I was cooked as a BBQ chicken. Long story short, they did great in the race and qualified for the world championships.

How it works. Repetitive workload in the heat boosts the organism ability to drift heat away from the body. The idea is to teach your body to trigger the sweat glands earlier and start lowering skin temperature right away. This should also result in better blood flow to muscles which should allow for better athletic performance during hot weather conditions.

General guidelines: The goal is to raise your core temperature to a high level to stimulate your sweat rate mechanism. For that, Perform moderate intensity activities for 60-90 min. Complete at least 4-8 total sessions during a 10-14 days span. Consider than other “passive” methods like saunas or other heat exposure might provide similar acclimatization gains. At the end of the process if your heart rate is lower, you’ve develop a higher sweat rate and thus your core temperature seats lower during exercise in the heat you’re all good. Read more HERE.


  1.  Adjust expectations. It would be wise to realize we are not going to perform our best in the heat. Don’t take me wrong, you can still go fast and compete at a high level! But your maximum potential will hardly be reached. If you embrace this mindset, chances are you can go into races with real, more reachable goals that will unload pressure and most likely let you walk away with a sense of satisfaction.
  2.  Adjust training paces. As we’ve been discussing above, heat will take a toll on your body, let’s not overloaded! On days when the temperature is scorching it’s no sin to back off the pace a little bit. Remember, the main purpose of every workout is to finish it, even if that means going slower than planned.
  3. Prioritize hydration. I’ll be sincere enough to admit I find it ridiculous when athletes walk around all day carrying a water bottle.  My general guideline is to drink regularly, don’t go too long in between intakes. Try to avoid over-drinking as this is not healthy at all.
  4.  In the shade now – then heat/sun. After all the research I did for this paper I’ve come to the conclusion that the best idea when training in hot weather is to perform the majority of the workouts in normal more stable conditions and then move on to acclimatization in the last phases of the training block. As evidence clearly suggested, athletes do not need to expose to harsh weather conditions all the time to be able to perform well in them.  So, let’s do the biggest chunk of training first in optimum weather and gain the fitness that will subsequently allows us to withstand the heat better, then we can go to the acclimatization phase as we taper. Voila!

You can read some more great ideas on dealing with hot weather, HERE.

Amateurs athletes more than anyone else should reconsider their training habits when living in hot weather areas. Heat has being clearly identified as a performance “detrimental factor” and possible health threatening, when symptoms are ignored. You can adjust your program in many ways including, hydration, training hours, pace & intensity. The fitter you are the better chance you have at dealing and performing better under hot conditions but acclimatizing is possible. Train smart, train happy,Good luck!