Heat exhaustion is serious, and it's not restricted to summer. Nutritionist Zoe Wilson takes you through the do's and don'ts of hydration and minimising risk on hot days on the bike.
Words: Zoe Wilson
As we hit the heights of summer, there are no better days for riding. However, long, hot days in the saddle require some smart thinking to keep hydrated, cool and riding all day.
We all saw the moment in triathlon as Alistair Brownlee was thrown over the line by his brother having worked his way into heat exhaustion. This too, can be you, if you’re not careful with your fluids when out on the trails. You don’t have to get to this point of dehydration for your performance to suffer, so it’s essential to prepare properly and sort out a fluids plan (and no, I don’t mean working out the quicker route to the pub…)
Why does dehydration matter?
As the temperature rises, your body tries to cool itself by sweating more, allowing you to keep exercising at intensity without cooking yourself. If there’s not enough fluid in the body (dehydration) this cooling method is compromised and your performance will suffer - a la Brownlee. Feeling thirsty is only the tip of the iceberg, dehydration also increases heart rate, effects concentration, reduces your strength and power output, increases your breathing rate and gives you a pounding headache - all of which make the effort during a ride much harder than it should be. On the more serious end of the scale, dehydration during exercise can lead to heat exhaustion and heat stroke with fatigue, dizziness, excessive sweating, nausea and, scarily, a loss of consciousness and even death. Bottom line? Dehydrated: bad; nailing your fluids and staying hydrated: good!
So, what can you do to minimise dehydration and keep riding strong all summer long?
To keep your drinks cool so you’re more likely to drink them, fill your bottles half-way and then freeze them. Pull them out in the morning and top them up before leaving. If you’re carrying a hydration pack, put ice cubes in your bladder.
Gauge your fluid requirements
During a ride, you’re aiming to replace the fluid lost through sweat, so the amount you need to drink will vary from person to person depending on how much you sweat. Knowing your unique sweat rate and how much fluid you should be drinking is important. The easiest way to measure your sweat rate is to weigh yourself without clothes before your ride. When you return home, strip off your clothes and towel dry before weighing yourself again. Assuming you did not use the toilet or drink anything during exercise, your weight loss is the amount of sweat you lost, so divide that by the hours spent on the bike and you’ll have your sweat rate.
If you drank anything during the ride or went to the toilet, you'll need to include both of these estimated weights in your calculations. Add fluid drunk to the amount of weight lost. Subtract estimated urine volume from the total weight lost.
Fluid loss example
Pre-weight = 70kg
Post-weight = 68kg
1L (1kg) drunk during the 2 hour ride
So: 70kg - 68kg = 2kg + 1kg = 3kg / 2 hours = 1.5kg/hr so you need to be trying to drink ~1L per hour (usually more than that isn’t feasible!)
And here’s the rub… Whatever you’ve lost, you need to drink around 1.5 times the amount in the following 3-4 hours to successfully rehydrate. So, in this case, thats 4.5 litres! (See why minimising dehydration during your ride is important?!)
Sip early and often.
Start drinking before you even set foot on the pedal and then keep it going throughout the ride. Have 2-3 glasses in the hour or so before you set off and drink a few big mouthfuls every 10-15 minutes while en route. This will help you to stay on top of things.
Drink all day
Stay on top of your hydration by drinking all day, not just during your ride. There’s nothing worse than starting behind the 8-ball. Check your pee during the day - if you’re doing a good job with your hydration your urine will be a ‘pale straw’ colour. If your urine is a dark yellow or orange, or you’re not peeing much, you need to be drinking more. Glass of water stat!
Sodium helps your body hold on to the fluid you're drinking and to stimulate your thirst, making it easier to drink more. Sip an electrolyte beverage during your longer or hotter rides. If it’s a particularly intense session you might also benefit from a sports drink. If you have two bottles, or a bottle and a bladder, fill one with water and the other with an electrolyte only or a sports drink.
Don't forget to eat!
Foods also contribute to our fluid intakes, especially fruit & veggies, so pack these into your daily diet. Also be sure to eat before and during a long ride (anything longer than an hour) and eat when you get home as well. This will maximise your performance during the ride, and reduce your recovery time so you can do it all again tomorrow.
Protect yourself & wear the right gear
Sunburn does more than increase your risk of skin cancer, it also increases fluid needs. Make sure you wear sunscreen and wear lightweight, breathable jerseys, shorts and even arm skins to keep your skin protected. For hot race days you might like to try a cooling vest or neck wrap, too. Especially in warm ups or between races if you’ve got a few rounds to do.