It stands to reason that when it is hot and we are exerting ourselves, our bodies will work harder. Our heart rate, oxygen consumption and the amount of carbon dioxide we will produce will increase due to our elevated core temperature. We may find ourselves working harder to maintain a pace in the heat that we find less demanding in colder temperatures.
Intermittent heat training in warm to hot temperatures has been shown to increase the efficiency of working muscles and sharpen our thermoregulatory response- increased ventilation, circulation and sweating. This in turn decreases our increased energy requirements associated with the the stress of running in heat.
The distinction of “warm to hot” not “hot to very hot” is important. Resist the urge to be a hero. Super hot outside? It’s probably unwise to be attempting a personal best distance or pace without some adjustment. Here are my two key training strategies to maximise benefit and minimise distress when running in the heat.
Plan to run slower. Expect to fatigue quicker, too. It’s easier said than done, but you need to adjust your expectations in terms of pace and distance. The heat will mean your heart rate is higher at a given pace. This is why the overall time you spend running is almost always more important than the actual distance you cover. What matters is the time you spend with your heart rate elevated. The physiological response will still happen as you recover, and you’ll be stronger for it. You can look to build speed at a more appropriate time of the season.
Start hydrated. Even more important than ingesting fluids on the go, your capacity to perform and run well is directly associated with how well hydrated you are when you take off. Your hydration status is quite simply the buffer between running comfortably and stopping at complete exhaustion – the bigger the buffer, the longer you’ll last.
Expect to need more water. I suggest you drink to thirst, though for what are hopefully obvious reasons thirst is likely to occur more rapidly / frequently in warm to hot conditions. Yes, thirst may be the first sign of dehydration, but only in the same way that hunger, is the first sign of starvation.
Saunders, P. U., Pyne, D. B., Telford, R. D., and Hawley, J. A. 2004. Factors affecting running economy in trained distance runners. Sports Medicine.