Running in the heat

How to maximise performance when the weather heats up.



by Alan Culpepper

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Over the last 15 years we’ve seen significant advances in this simple sport we know and love. GPS, heartrate monitors, chip-timing, space-age gear, high-tech gels – there’s so much new stuff under the sun compared with when I started my professional running career. So why does it seem that our thinking about running under that sun – heat adaptation and hydration – is stuck in the 1990s with my bad jeans and REM tapes?

A trip to Texas with my family got me thinking about heat, fluid loss and performance. My dad came back from an easy five-mile run. It was about 18C, overcast, and humid. His 1997 grey cotton race T-shirt was saturated. Granted, unlike the synthetic fibres in modern running apparel, the cotton shirt didn’t wick an iota of sweat. Still, it wasn’t really that hot, and he was drenched. It got me thinking about how much heat factors into our training, and that if his shirt looked like that on an 18-degree day, what would a 38-degree day be like? So, how much does heat affect our performance? Why do most runners still struggle with adapting to it? And how can we run better – and safer – when it gets hot out there?

How heat hits performance

There are three main physiological effects of heat on performance. First is dehydration and the associated sodium loss. Although we lose other electrolytes and minerals through sweat, sodium loss is felt the earliest and most significantly. Second is increased heartrate. As our bodies try to cool themselves, our hearts work harder. This links to the third effect: more blood being sent to the skin, away from our running muscles. So, electrolytes pour out, heartrate goes up, blood flow gets diverted and performance goes out of the window.

There is good news, however: heat acclimatisation is trainable. We can teach our bodies to become more efficient at losing heat and holding on to precious electrolytes. After grinding through the winter months 

our bodies are ineffective at losing heat, and we also lose more sodium through our sweat. As we force them to acclimatise, our bodies adapt to get better at losing heat, and lose fewer electrolytes through sweat.

The real bonus of heat acclimatisation is that it leads to better performances regardless of the temperature. If you’re adapted to heat, then obviously you’ll perform better in warmer conditions; the cool thing is that studies have shown you’ll also perform better in optimal conditions. Our bodies have to work hard when dealing with the heat, and this creates an environment for advancements in overall fitness. As we get fitter, everything becomes more efficient. Along with more effective heat loss and better electrolyte balance, our absorption of fluids, metabolism, recovery rate and ability to flush out lactate all improve.

Just add water?

In warmer weather, your primary emphasis should be on hydration and electrolyte intake before, during and after running. And, no, I don’t mean five cups of coffee before an early-morning run followed by a steady intake of Diet Coke for the rest of the day. Hydration must be considered and play an integral role in your training. See it as of equal importance to your long runs, tempo runs and threshold training.

Now, I’m certainly not advocating consuming huge amounts of water; hyponatraemia [dangerously low blood sodium levels] is known to be a risk for people who drink excessive amounts of nothing but water before and during long training runs and races. What I mean is consistent hydration. Water should be the main source before runs and throughout the day, and some variety of electrolyte drink should be the primary form during longer runs and immediately after.

There’s too much emphasis on fuelling when the focus should be on electrolytes. As a result, many people are functionally dehydrated, meaning their bodies have become accustomed to not having the proper amount of water in their system.

This can become very problematic come race day. They start drinking more in the few days leading up to the race and drink at every aid station, and struggle to finish strong or suffer severe cramping. In race conditions, our bodies send very little blood to the gut because it’s needed in the working muscles, so gastric emptying becomes more challenging. You need to practise in long training runs and some tempo efforts so your body adapts and becomes more efficient at absorbing the fluid during competition.

NOW Warm up!

In cooler conditions, you can reap more from your training by being proactive in creating warmer conditions. Over-dressing is the easiest, most effective way to do this. East African and Japanese athletes wear full tracksuits during the summer months for every run aside from their hard sessions. Although it’s not pleasant, doing so forces your body to adapt.

A tracksuit may not be necessary, but wearing a long-sleeved top over a T-shirt, plus a running cap, is a good start. I’ll never forget warming up for the 10,000m at the 2003 World Championships. A heat wave in Paris meant temperatures were in the mid-30s, and the Ethiopian team warmed up in full tracksuits for a solid hour in the heat of the afternoon. Had I attempted to do the same I would have been peeled off the track and carted to hospital. They went on to run the second 5K of the race in under 13:00. I decided to move up in distance.

A year later I ran the Olympic Marathon in Athens in 32C heat. In training, I’d overdressed consistently on my recovery and long runs, and during the race I drank sodium-concentrated Gatorade. I managed the conditions well. Eleven athletes finished ahead of me, but no Ethiopians. The mantra ‘mind over matter’ also applies to heat adaptation. Focusing on how oppressive, suffocating and unbearable the heat is will only serve to make it that much more oppressive, suffocating and unbearable. So instead focus on the positive aspects – that adjusting to the heat and embracing its inevitability will help you get fitter. Be aware of your hydration throughout your training, but particularly in summer. Be positive, take in those electrolytes, put on an extra long-sleeved shirt or even bust out that grey cotton tee and sweat it out.


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heat training, running in the heat, hydration, summer
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