Heat and Exercise Performance

BY IN Exercise Institute News On January 28, 2017

The effect of heat on an exerciser can be catastrophic. We look at some of the data used to quantify the toll of heat on a working body, namely a cyclist, and review some acute and chronic training systems  used to offset the negative effect of heat.

Cyclists exist in a micro-climate unique to their sporting discipline, that being 1 meter above a black surface that absorbs and radiates heat, usually meaning if it is a 35c day they are riding around in 40-43c temperatures owing to the black road surface. The effect of heat on the human body has been well documented, see here. Recently at the Ring Criterium Series in Perth Western Australia racing was held in very hot conditions of 45c as recorded on the Garmins attached to the bikes during the race. Ambient air temperature was around 35c in this instance.

In the image below the shaded area is this cyclists peak 5 min power output, occurring after 5 mins of activity. Here, the individual established a break and rode hard to maintain their advantage. However as is indicated in the image beneath this, the maximum 5 min heart rate occurred toward the end of the race. Considering heart rate and power are very well correlated, meaning heart rate rises as power rises, this is demonstrative of a ‘cardiovascular drift’ or increase in internal work rate for a given output owing to several physiological responses, but pronounced in this instance by the heat.


Peak 5min power output


Peak 5min heart rate

In fact across this race the athletes heart rate increased by 18% for a given power output. We reviewed around 10 athletes power/HR data on this day with this response very much the norm.

This decoupling is HUGE and would certainly be associated with performance decrements. There are however several strategies that can be utilised to offset this extreme response. The body is very trainable to heat, meaning training in the heat can be very beneficial for endurance exercisers. Another aspect worthy of attention is pre-cooling, or reducing the body’s core temperature prior to the start of activity such that their is a buffer between the time taken to reach a critical internal temperature associated with performance degradation’s.

HEAT TRAINING, see here for more information, can be completed within a week and adaptation will occur. By simply training in the heat the body becomes more efficient in these environmental conditions. Some research has shown a benefit of approximately 5% in performance terms with heat adapted athletes.

PRECOOLING, see here for an overview, involves the ingestion of ice and dousing of water whilst the athlete warms up. For cyclists this is relatively easy as a warm up can be completed on a stationary trainer whilst ingesting ice, dousing water, etc. Depending on the nature of exercise the benefits of pre-cooling can be between 3-8%

In conclusion it is evident heat has an incredible toll on the body’s ability to perform. Fortunately an athlete or exerciser does have options that can be explored and utilized to better assist them during hotter conditions. Exercise Institute regularly holds indoor heat training classes and has successfully completed pre-cooling strategies to a large range of athletes. Please contact us for more information.

Brad Hall
B.Sc. (Psy & Sport Sc.); B.Psy (Hons)


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