Training in a heatwave could make you fitter – if you do it safely

With temperatures soaring above 30’C, working out may sound less appealing than usual. But studies have shown that there could be some real performance benefits to sweating it out. Personal trainer, nutrition coach and heat training devotee Devinder Bains explains all…

We’re in the midst of a super-strength heat wave, and with temperatures set to soar above 30’C you might be thinking more about staying indoors rather than heading out for a long run or bootcamp session in the park. Working out in the heat, however, may mean reaping health and fitness rewards once the weather cools down again.

In fact, a number of studies have concluded that heat training can improve fitness, with researchers at the University of Oregon seeing a difference after just ten days of heat acclimation before returning test subjects to train in cooler conditions. Another study by the University of Otago in New Zealand noted improved performance after just five days in elite athletes. 

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So how does it work? Simply put, training in the heat means the body has to work harder because the conditions are tougher. Over time, your body starts to adapt and gets more efficient at sweating and cooling itself down, and better at making oxygen available to the heart and muscles. 

When you return to a less hostile environment, that same workout will feel easier because your body has made positive physiological changes. Let’s take your weekly 5km, for example. If, over the next few weeks, you got used to running it in 28°C and began to find it comfortable, when you returned to running the same distance at the gym or in cooler temperatures, you’d find it much easier, meaning you could run a bit faster (or further) and smash that personal best.

Why is heat training so good for us?

To understand why that is, we have to look at what’s happening in the body. Training in the heat causes an increase in the body’s blood plasma volume – this is the liquid portion of the blood. This happens for a number of reasons. Firstly, the loss of water through sweating means the body needs more fluid; secondly, more blood needs to be transported to the skin to help it cool down by increasing sweat rate. This means that there’s less blood left to get oxygen to the heart and muscles – driving a further increase in blood plasma volume.

Then, when your workout conditions become less hostile (eg the weather cools down), you still have this increased blood plasma volume to tackle your regular training. Now, you can transport a greater amount of blood with performance-boosting nutrients and fuels like oxygen all over the body. This is particularly useful during aerobic exercise as there’s an increased need for oxygen to the heart and the muscles.

Another performance benefit is that you become better at cooling yourself down through sweating. By shunting blood to the skin and opening pores, you allow some of the fluid in the blood plasma to secrete (sweat). This then gets evaporated from the skin into the air and helps draw heat away from the body. 

When you return to training in cooler climes, you will, of course, still heat up as you work out but your body will have become more efficient at cooling down – putting less heat stress on the body during workouts than before.

Which kinds of training work best in the heat?

You’re most likely to see performance improvements in aerobic exercise such as running and cycling because these are the ones that most benefit from increased oxygen availability. 

This makes heat training particularly useful for endurance athletes and for those looking to run longer distances or faster times. But that doesn’t mean you can’t mix up your training. Moving other sessions such as boxing and bootcamp outdoors can also have the same positive impact on the body and in turn improve your running PBs.

How to start heat training

Training in 25°C temperatures isn’t without its risks – heat stroke, dehydration and sunburn are all potential issues, as is bloating. Because of this, the transition into heat training needs to be done gradually, taking necessary breaks and staying hydrated. 

When starting out, either decrease the volume or intensity of your normal workout to compensate for the more difficult conditions and then slowly work yourself back up. This means that if you usually do a one-hour boxing session inside, then scale back to 30-40mins for the first two weeks outdoors, or if you usually run a 5km in 30 minutes in the gym, slow down your pace or cut down your distance until you get more used to the conditions. It’s important to know your limitations. 

Choose slightly cooler days when starting out and always avoid the triple threat of heat, humidity and direct sunlight. If you’re worried that scaling back will affect your immediate goals – maybe you have a race coming up – then start by adding just one outdoor session a week until you’re able to match your indoor performance. 

More generally, start with two outdoor sessions for the first two to three weeks, then start scaling up to your usual volume and intensity. By week five, you should be able to manage three outdoor workouts. From here, you can start heading out in the hotter parts of the day – again avoiding the triple threat.

Fuelling hot workouts

You might also want to start thinking about electrolytes, if you haven’t already, as drinking large quantities of water in the heat can mean you risk flushing out too many essential minerals through sweating. Electrolytes are readily available to buy as rehydration tablets that can be added to water and consumed before, during and after heat exercise depending on the type and duration of the workout.

Another consideration is clothing: avoid water-absorbing heavy materials and opt for kit that allows sweat to wick off. Invest in a hat or cap (some come with neck coverings too). For brighter days, grab some running or cycling sunglasses and wear lightweight socks that don’t get super sweaty – running stores are actually great places to get specific advice.

Is heat training worth the faff?

Is heat training worth the effort? In a word: yes! I have used heat training to advance my own endurance running (both distance and times) for a number of years. I’ve even used heat training chambers – heated rooms that test how you’re coping with the temperature. If you’re interested, they often have these on university campuses so it’s worth putting in a request to be a test subject. 

I also practice hot yoga in the colder months, which is a great way to acclimatise to the heat in a safe environment before you head outdoors. The benefits of heat training are definitely worth exploring; in addition to improved blood circulation, heated practice is a great overall cardiovascular workout that improves stamina and flexibility. 

Oh, and there’s nothing like the endorphin rush after a sticky, hot session!

For more training tips, workout plans and healthy recipes, visit the Strong Women Training Club.

Images: Mark Field Photography

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