It’s heatwave season and soaring temperatures are adding an extra challenge to our workouts. How can you mitigate the effects, stay cool and keep exercising?
To be able to perform well in the heat, you need to be efficient at shedding heat and replacing lost water – but how exactly?
What happens in the body when you exercise in the heat?
The fatigue and loss of power you experience during very warm weather workouts is caused by two main factors: a rise in core body temperature and changes in your metabolism. Both the exercise itself and the air temperature and humidity can increase your core body temperature, putting stress on your cardiovascular system.
To help cool itself, your body sends more blood to the skin. This leaves less blood available for your muscles, and your heart has to work harder. Losing fluid in the form of sweat through the skin means blood volume decreases and your heart’s stroke volume decreases.
The most effective method of getting rid of excess heat during exercise is sweating, whereby the moisture on the surface of your skin cools you down as it evaporates. Staying on top of your hydration is crucial when exercising in the heat.
Dehydration difficulties
Hot conditions plus dehydration can lead to a drop in performance and, at worst, a dangerous rise in your core body temperature. If your body’s temperature exceeds 39ºC, you’ re at risk of developing heat-related illness – heat stress, heat exhaustion and heatstroke – stated in ascending order of severity.
Generally, performance starts to decrease when you lose 2% of your body weight as fluid through sweating. You may see anywhere between zero and 20% drop in performance.
Cooling strategies
Reduce the duration and intensity of your workout.
Exercise early in the day or later in the evening to avoid the worst of the heat – avoid exercising in the hottest part of the day
If you’re exercising outdoors, seek the shade as much as possible.
Sip an ice-cold drink or ice slushy (crushed ice + water) just before you exercise – this will pre-cool your body
Pour or spray water over your skin to aid heat evaporation
Put ice cubes inside your helmet, socks or jersey.
Make sure you’re hydrated
Dehydration is a key factor in heat-related illness. Staying hydrated helps your body sweat so will help lower your core temperature. Ideally, you should drink enough so that you keep your fluid loss below 2% body weight. That’s equivalent to a weight loss of 1.4kg for a 70kg person.
If you’re doing exercise that lasts less than two hours, where sweat losses are relatively small, you should only drink when thirsty. Over-hydrating can be as problematic as dehydration, causing a potentially dangerous imbalance in the body’s salt levels.
But if you’re sweating heavily or exercising longer than 2 hours you may need to be more proactive in your drinking strategy to avoid becoming dehydrated.
Can electrolytes help performance?
Although you lose electrolytes in sweat, you don’t need to replace them during workouts of less than two hours. You have enough sodium in your body to replenish sweat losses. By taking extra sodium in tablets, you could be pushing your overall salt intake too high. Only athletes sustaining heavy sweat losses, for example during workouts or races of longer than two hours are likely to see any benefit. But even then, the benefit is on longer-term sodium balance, not performance in any single event. It is a good idea to replace sodium after exercise, though most of us have plentiful salt in our regular daily diet to cover these needs.
Riders who suffer from cramps during long, hot rides, sportives or races often blame poor hydration or lack of electrolytes. However, recent studies have indicated that this isn’t always the case, and the exact reason for cramping is still unknown.
Heat adaptation training
If you know you’ll be racing in hot, humid conditions, doing heat adaptation training a few weeks beforehand will help you perform better.
If you can’t travel to a hot country before your race, the alternative is to simulate the conditions by wearing extra clothing while training or immersing yourself in a hot bath (40ºC) for 45 minutes.
You’ll need to raise your core temperature by 1.5ºC for at least 60 minutes daily for 10 – 15 days until a few days before your target race.
How do you know whether you know whether you are heat adapted? Your resting and exercise heart rate will be lower for the same power output, and you’ll start sweating earlier in your session or at a lower ambient temperature.
The Complete Guide to Sports Nutrition, ninth edition is the definitive practical handbook for anyone wanting a performance advantage. This fully updated and revised edition includes guidance on:
maximising endurance, strength, performance and recovery
the most popular sports supplements
relative energy deficiency in sport (RED-S)
hydration strategies
nutrition for masters athletes, young athletes and plant-based athletes
nutrition preparation for competition
gut health and how to avoid gut problems during exercise
This year’s Prudential RideLondon-Surrey will see around 100,000 amateur cyclists take to the streets of London in the UK’s biggest festival of cycling. It includes a number of road races for professionals but keen riders will also be taking part in the sportive event: a 100-mile ride from London to Surrey on a similar route to that of the London 2012 Olympic Road Cycling race. So how do you fuel your body before, during and after an event like this?
Avoid ‘bonking’
The key is to start the ride with full stores of glycogen (carbohydrate). This will not only help fuel your leg muscles and increase your endurance but will also reduce the chances of you ‘bonking’. This is the cycling term for that terrible feeling when you’ve nothing left in the tank: your legs turn to jelly, you feel weak, dizzy and disorientated and can no longer keep pedalling. It happens when you have depleted your body’s glycogen stores.
It’s hard to get back from a ‘bonk’ so your best protection is to ensure that your glycogen is fully topped up before starting and then to refuel throughout the ride. The former is achieved by carbohydrate loading – tapering your training during pre-ride week and increasing your carbohydrate intake. The ACSM recommend 10 – 12g carbohydrate/ kg of body weight per day in the last 48 hours before the event (700 – 840g/ day for a 70kg cyclist).
That may sound a lot but, in practice, you simply need to ensure you include a decent-sized portion of high-carb foods such as porridge, potatoes, pasta, rice, bread, fruit and pulses in each of your meals. But don’t take it to extremes and eat too much, otherwise you may wake up feeling heavy and bloated on event day. Carb loading doesn’t mean eating as much as you can!
The day before
Stick to the foods you normally eat and don’t experiment with anything new. Eat plain and simple meals, including a portion of carbohydrate and a portion of protein. A simple tip is to eat most of your food at breakfast and lunch rather than a big meal late in the evening. Little and often will help maximise glycogen storage. And keep hydrated – sip on water frequently throughout the day.
Try to minimise fibre (e.g. by swapping wholemeal for white bread) and steer clear of anything that may cause digestive issues and jeopardise your performance. On the other hand, if you’re fine with these foods, then there’s no need to avoid completely. Suitable meals include a chicken or chickpea tagine (stew) with couscous, Pad Thai (noodles) with tofu or chicken, or a simple risotto with butternut squash, beans and peas
The morning of the ride
If you’re doing RideLondon, you’ll have an early start so may not feel like eating breakfast at 3 or 4 o’clock in the morning! However, eating something rather than nothing beforehand will help delay the onset of fatigue and means you’ll feel better during the ride. How much and what you eat before the ride will depend on how much time you have between waking and the start of the ride. The less time you have before your ride, the smaller your meal should be.
Have a breakfast you’re used to. This should contain foods rich in carbs and protein to help keep you satiated. If you are able to eat at least 2 hours before riding, try porridge with fruit and nuts; overnight oats (or Bircher muesli) or granola with fruit and yogurt. If you have less than 2 hours or you simply can’t face a meal, opt for an oat bar, banana or smoothie. It’s important to start the ride hydrated, so sip water frequently and aim to drink 350- 500ml fluid 2 – 3 h before you start riding.
Many cyclists like to include coffee for a pre-ride caffeine boost. But not everyone responds well to caffeine (it may cause trembling and headaches), so don’t try it for the first time before an event. In studies, it’s been proven to increase alertness and lower perception of effort, making cycling feel easier and increasing endurance. The current consensus is approx 1 – 3mg/ kg body weight, that’s equivalent to a double espresso but you may prefer pills, gels or chews.
During the ride
Start refuelling within the first hour or so, and then refuel every 30 – 60 minutes, aiming for a total of 30 – 90g carbohydrate/ hour. The exact amount you need depends on how hard you’re riding. For example, cycling fast or uphill burns proportionally more carbohydrate than fat compared with cycling at a leisurely pace or on the flat, so you’ll need consume more carbs during these stages. You can get 30g carbohydrate in the following:
1 large banana
40g (a small handful) dried fruit
1 Oat bar or 2 Nakd bars
500ml sports drink (6% carbs)
1 energy bar
4 energy chews
1 energy gel
Refuelling during the ride helps maintain blood glucose levels within an optimal range and supply additional fuel to your muscles. This reduces the rate at which your muscles burn glycogen and thus helps stave off fatigue.
Take high-carb snacks that you have trained with, including savoury options (e.g. peanut butter or Marmite sandwiches, rice cakes and pretzels) as well as sweet to reduce flavour fatigue and the risk of tooth damage. You may want to take natural foods (e.g. fruit and nut bars, bananas, flapjacks and dried fruit) as well as energy products (e.g. gels and bars), whatever you’ve trained with. Use natural food nearer the start to give it time to digest, energy products nearer the end when you need a quick boost. Prepare as much as possible e.g. cut bars in half and open wrappers to make them easier to consume, and put them in your pockets. If you wish, you can use caffeine during the ride to make it feel easier, increase focus and reduce fatigue – but only if you’ve used it successfully in training.
Take two refillable bottles: one for water and one for a sports or electrolyte drink (or whatever you used during training). Your aim is to avoid under-drinking (dehydration) as well as over-drinking (hyponatraemia). Drink little and often and to thirst; the amount you need depends on your sweat rate, which will increase during hot humid weather and on climbs. Aim for approximately 400 – 800ml/ h. Drinks containing electrolytes are recommended on long hard rides over 2 hours or when sweat losses are high (especially if you’re a salty sweater).
Check in advance where feeding and drinks stations are on the route. Use the opportunity to re-fill your bottles and stock up with food – but avoid over-eating! Be wary of trying new products – stick to what you’ve trained with.
Recovery
When it’s all over, following a few simple rules for recovery will help you feel better in the following few days. Sip water or a sports or electrolyte drink – rehydration can take up to 24 hours so continue drinking frequently. You’ll need carbs and protein to refuel your glycogen and repair damaged fibres in your muscles. Good options include milk-based drinks, recovery drinks, cheese sandwiches, yogurt, protein bars, flapjacks and bananas. Then go ahead and celebrate! Suitable recovery meals include rice and fish, or sweet potatoes with cheese or hummus and salad.
If you want more advice..
I’ll be on Centre Stage at the 2019 Prudential RideLondon Cycling Show, giving five talks each day with lots of simple, practical tips. The Show is free to enter, open to all and runs from Thursday 1st August until Saturday 3rd August.
More than 100 delicious, easy-to-prepare vegetarian and vegan recipes for healthy breakfasts, main meals, desserts, sweet and savoury snacks and shakes.
Expert advice on how to get the right nutrients to maximise your performance without meat
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Full nutrition information for each recipe, including calories, carbohydrate, fat, protein and fibre
The Complete Guide to Sports Nutrition, ninth edition is the definitive practical handbook for anyone wanting a performance advantage. This fully updated and revised edition includes guidance on:
If you enjoyed this post and want to find out more about food and nutrition, as well as some easy and tasty meal inspiration, then