Ice Ice Baby: Controlling Core Temperature Before, During, and After Exercise in Hot Weather

“All right stop, collaborate and Listen, Ice is back with…” No, no, no. Not that “Ice Ice Baby”.

Exercise generates a ton of heat; about 75% of the energy you expend to propel a bicycle is lost as heat and only about 25% of it actually produces work. A hot summer environment only exacerbates the challenge. Here are some ways you can take advantage of proven thermoregulation techniques to achieve real improvements in comfort and performance this summer.

To understand how to best use cooling techniques, it is useful to understand what you’re up against. The heat you generate has to be dissipated in order to keep core temperature from rising to levels that first hinder performance and then can become dangerous to your health. Sweating is your primary cooling mechanism, and while many people focus on dehydration as the cause of rising core temperature, I think it’s better to look at it the other way around. It’s the heat that’s driving sweat rate, and you can reduce your hydration stress by broadening your approach to staying cool.

Cooling techniques can be divided into three categories: pre-cooling, per-cooling, and post-cooling.

Pre-Cooling

The goal of pre-cooling is to give you more time to exercise before core temperature rises above normal. Pre-cooling techniques only provide a temporary reprieve from the effects of exercising in hot weather, but along with steps taken during exercise (per-cooling) it can mean the difference between finishing strong or fading too soon.

The most effective pre-cooling techniques are unfortunately the least practical. Whole body immersion in cold water is hard to arrange by your car before the local criterium. Your most practical and effective choices are ice slurry drinks and either an ice vest or wrapping/covering yourself with cold, wet towels. Use the vest/towels for up to an hour. It’s not just internal temperature that matters. Elevated skin temperature is one of the contributing factors that lead to increased blood flow to the skin. Going to the start line with a wet jersey or an ice sock between your shoulder blades can help as well.

Per-Cooling

Pre-cooling might give you a head start, but you have to stay on top of proactive cooling to stay ahead of the heat. One difference between pre- and per-cooling is that a cold drink is optimal during exercise in the heat instead of an ice slurry drink. The research suggests this may be due to temperature sensors in the stomach. The ice slurry drink may trick them into slowing or diminishing cooling mechanisms like blood flow to the skin and sweat production. This in turn increases heat storage, which is exactly what you want to avoid!

Beyond drink choice, the other per-cooling choices are pretty obvious. Getting wet provides evaporative cooling and may slow sweat rate. Removing layers, wearing lighter colors and thinner fabrics can all help. Training at cooler times of day is a great option, but you won’t have much say in the timing of events and races.

If you have limited water it’s best to drink it rather than using it to cool your skin. You are more likely to find other opportunities to cool your skin (shade, a headwind, a stream) than you are to find other opportunities to ingest fluids.

Post-Cooling

Bringing your core temperature down following exercise in the heat is beneficial for recovery, and whole body cooling is more important than cooling specific muscles. Sitting in an ice bath was long thought to be beneficial for reducing inflammation. More recent research is still somewhat inconclusive on the potential benefits from ice baths, but an important change to our understanding of recovery is that inflammation should not necessarily be avoided or minimized.

Inflammation associated with trauma or injury is different than inflammation as a response to normal exercise. Following a hard workout or race, you will have some inflammation in working muscles. But that inflammation may be a key component of the training stress that results in adaptation and progress. When you immediately jump into an ice bath following a hard workout you may actually be blunting the training stimulus from all that hard work.

A more effective way to enhance recovery is to take proactive steps to cool your whole body. These steps include cold water or ice slurry ingestion, covering large areas of the body (torso) with cold towels, taking a cool shower, or immersing your body in cool water (not icy water). And later, if you are having trouble sleeping following a hard workout, especially on a hot day, try reducing the temperature of the room.

Performing in the heat isn’t just a matter of getting more fluids into your body so you can sweat more. With proactive cooling strategies before, during, and after exercise you can produce more power and do more work before heat diminishes performance, reduce competition for limited blood volume, and improve sleep quality to improve recovery. This summer your mantra needs to be: Chill Out.

Chris Carmichael
CEO/Head Coach of CTS