Wednesday, 3 September 2014

Nutrition : What to Eat (and Drink) During Exercise

As my workouts are getting increasingly longer in preparation for my Autumn and Winter events, I'm starting to think more about how I should fuel myself during these sessions, to get the best out of them. My Personal training studies have covered this and I thought it might be useful to share what I've learnt.


If your workouts are usually 60 minutes or less, then you won't need to think about eating during a session. Your body generally has enough energy stored in the muscles to cope with an hour or so but after that those stores benefit from being "topped up".  As I'm now doing longer sessions, in preparation for my longer events in the autumn and winter, I'm having to think about fuelling up on the go.

Although the body gets most of its energy from fat, fat doesn't metabolise very quickly so carbohydrates are the fuel of choice during exercise. You're looking to take on 70g of CHO per hour, starting about 30 minutes into your session; think little and often over the course of your workout.

What you consume is worth thinking about. Your body needs that energy source quickly so a high GI food is perfect. Bananas and dried fruits are good options if you can handle solid foods, 500-1000ml of isotonic drink also work well and tend to be easier to consume on the go or in the gym and lots of runners take gels or jelly sweets. The options are varied but ultimately it comes down to what you can stomach. The sports drink you sip in the gym probably won't be enough on a long run and you might not be able to face the gels you eat during a triathlon when you're running an ultra (for example). A cheese sandwich might appeal more!


In addition to fuelling it's important to keep properly hydrated during exercise. Even if you're 2% dehydrated it can seriously affect your performance and your general feelings of well-being. As you dehydrate your blood becomes thicker and it takes more effort for your heart to pump it around your body.

So how to stay hydrated? You need to drink approximately 1ml of fluid for every kcal burned or 1.5 litres for every kilo lost in weight during exercise. The best way to accomplish this is by drinking little and often throughout your event or training session. I've been known to pop into pubs on my running route to top up on water. Indeed, water is all you need for sessions lasting less than an hour but a sports drink is more beneficial for longer sessions. There are three main types of sports drink, all of which have a different purpose:
  • Isotonic provide carbohydrate and maintain hydration
  • Hypotonic designed to maintain hydration
  • Hypertonic used to supply carbohydrate 
During exercise you'll want an isotonic or hypotonic drink as these are less sugary and energy dense which allows the fluid to be absorbed more rapidly. There are plenty of sports specific drinks on the market (I'm a particular fan of nuun - see the side bar for a discount code), just make sure what you're buying suits your needs, but you can easily make your own.

  • 500ml water
  • 500ml fruit juice
  • pinch of salt
  • 750ml water
  • 250ml fruit juice
  • pinch of salt
A final word on hyponatraemia. This is a condition that occurs when your blood sodium levels become too diluted. You've probably read about the occasional marathon runner who has suffered from this. It tends to affect those who are new to exercise or cover longer distances like ultramarathons or triathlons, as they tend to sweat more and have longer to take on fluids. have recently featured a great article about this, from a personal point of view and I'd recommend you give it a read. But don't get scared off of drinking during exercise. It's important to rehydrate, just make sure you include a little sodium as well.

Now I just need to start following my own advice! How do you fuel or hydrate during exercise? How do you carry it when you're out and about?

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