What should I eat during exercise?

A few weeks ago we discussed the importance of fuelling your body properly before your workout. Having a good pre-exercise meal or snack will make a huge difference to your exercise performance and will help avoid gastrointestinal discomfort during exercise. But what about fuel during your workout?

In most conditions, all you need to worry about during your workout is making sure you’re hydrated. Water is so important as it helps transport carbohydrates, vitamins, minerals and other nutrients to your cells to make energy. So dehydration slows down the delivery of all these nutrients. During exercise, you lose a lot of water through sweat and breathing, so you need to make sure that you’re replacing this fluid loss throughout the workout. Don’t wait until you feel thirsty! Sip water early and at regular intervals.  

If you are working out for longer than an hour, and at a very high intensity, you might consider having some carbohydrates as mid-workout fuel, or some branch-chained amino acids if you are doing strength training. Here are some basic guidelines:

• For exercise <1 hour, sip water early and regularly.
• For exercise lasting 45-75 minutes, a mouthwash of carbohydrate solution can help offset nervous system fatigue.
• For 60 minutes-2 hours, 30 grams of carbohydrate per hour should be enough to offset low blood sugar and performance decrements. Applesauce is a good example, as it’s easy to digest and will give you carbohydrates in that 30g range.
• For 2-3 hours, increase to 60 grams of carbohydrate per hour.
• For really long sessions (>2.5 hours), you will require 80-90 grams of carbohydrate per hour (a mixture of glucose and fructose will help with absorption).
• If you are doing workouts that cause muscle breakdown - like sprinting or strength training - you could consider adding a branched-chain amino acid (BCAA) solution to any of these options. BCAAs have been shown to prevent muscle breakdown during exercise.

Your mid-workout fuel can be in the form of a beverage, gel, or bar depending on your personal preference. Just make sure that you choose something with low amounts of protein, fat, and fiber, as these will take too long to digest. 

Sports drinks are designed to provide us with the right amount of carbohydrates as well as electrolytes to make up for those we lose while sweating. However, most commercial sports drinks have a lot of additives. You could consider other options such as watermelon juice, coconut water, or a simple homemade drink consisting of water, lemon juice, and a pinch of salt to help replenish your body with carbohydrates and electrolytes lost during your workout.  

Play around with what works for you. Just like pre-exercise nutrition, what your body needs during a training session is individual and will also depend on the condition, as your body will have different needs if you’re exercising in a hot environment or at a very high intensity in which you're sweating a lot. Remember, if you’re working out for less than an hour, water is all you need!

What are we finding in the research?

Recently, a group of researchers studied the factors that affect hypohydration (dehydration) during training in elite male soccer players. They studied the difference in sweat rates, dehydration, and fluid intake during four different environmental and exercise intensity conditions: 1) cool temperature, low intensity (Cool/Low), 2) cool temperature, high intensity (Cool/High), 3) hot temperature, low intensity (Hot/Low), and 4) hot temperature, high intensity (Hot/High). The researchers discovered that environment and exercise conditions significantly affect sweat rate and dehydration, with the greatest fluid loss during the Hot/High condition. However none of the players experienced fluid loss greater than 2% body mass, the point at which hypohydration significantly impairs exercise performance. This is likely due to the increase in fluid intake that accompanied a higher sweat rate.