Do I Need to Refuel Mid-Workout?

A quick guide to workout nutrition

Muscles need fuel to function—that much is clear. But besides optimal pre- and post-workout nutrition, does the body ever need an extra energy boost mid-workout? Studies show there may be some benefit to refueling during a workout—but what and when isn’t the same for everyone[1].

Fuel for Thought: The Need To Know
To run, to lift, to tumble—muscles first turn to carbohydrates (think: fruits, veggies, grains and dairy) for energy whenever they’re present in the body. Muscles then store those carbohydrates as glycogen, (also available in the bloodstream and liver). But once the body gets moving, we start dipping into that stash—begging the question, are we sure there’s enough? Research suggests it all depends on the type and duration of exercise.

While shorter, low-intensity workouts (like a 15-minute stroll or a few core exercises during a commercial break) can usually make do with what’s stored naturally, an extra energy fix can be clutch during high-intensity, long-duration exercise. (Distance runners don’t stock those fanny packs with energy gels, chews, and jelly beans for nothing!) But why simple carbohydrates rather than a colossal protein bar or big ol’ whole-wheat bagel? Research shows that protein, fat, and complex carbohydrates (those with lots of fiber) can often take too long to digest to be effective fuel for the exercise at hand.

Refuel Right—Your Action Plan
From prepping the gym bag to perfecting that game face, we know there’s plenty to do before hitting the gym. Let’s see if a pit stop at the fridge (or vending machine) should be added to those to-do’s:

• For cardio sessions under an hour: Drink responsibly. Sipping sports drinks intermittently has been shown to improve performance, though many experts warn not to overdo it[2]. There’s no need for the extra sugar and calories when the body—if fueled properly all day long—can sustain performance without the boost.

• For cardio sessions over an hour: Readily refuel. Proper carbohydrate replenishment (and hydration) is key. The Academy of Nutrition and Dietetics recommends active individuals consume approximately 0.7 grams of carbohydrates per kilogram of body weight (usually about 30-60 grams, depending on the type and intensity of activity) per hour of endurance exercise[3]. So on a big cardio day, that could mean a 32-ounce sports drink or two small bananas, consumed intermittently throughout the workout. (If going with a fuel source without much water content, just be sure to load up on fluids, too.)

• For weightlifting sessions: Go easy. Drinking sports drinks in between sets has been shown to keep glycogen stores in the muscles full, but it likely won’t increase performance[4]. Consider skipping the sugary stuff and opting for water instead.

• For the big game: Keeps carbs close. It seems there’s some science behind Gatorade showcasing basketball and soccer mega-stars in action—drinking sports drinks during high-intensity exercise might, in fact, improve performance[5]. See a doctor if you begin to sweat purple, though!

Keep in mind that a person’s metabolism, age, gender and weight are all factors in the refueling game. And listening to the body is key: Light-headedness, nausea and (excessive) fatigue should not come with the territory.

Also, some anecdotal evidence shows that suddenly adding major doses of carbohydrates to a workout routine can result in discomfort, upset stomach and diarrhea (ick, it’s true). Of course, everyone’s different, so a little trial and error can never hurt—just be sure to do it before game day! So whether we’re Kobe or just an average kid in the weight room, remember that optimal performance can’t happen without the right fuel before and during showtime.

The Takeaway
While moderate doses of simple carbohydrats might improve performance during cardio, not all exercise requires a mid-workout reboot.

Kyle J. Smith


Works Cited

1. Effect of carbohydrate ingestion on sprint performance following continuous and intermittent exercise. Sugiura, K., Kobayashi, K. Medicine and Science in Sports and Exercise, 1998 Nov; 30[11]:1624-30.
2. Carbohydrate-electrolyte feedings improve 1 h time trial cycling performance. Jeukendrup, A., Brouns, F., Wagenmakers, A.J., et al. International Journal Of Sports Medicine, 1997 Feb;18[2]:125-9.
3. Carbohydrate ingestion during prolonged exercise: effects on metabolism and performance. Coggan, A.R., Coyle, E.F. Exercise Sport Science Review, 1991;19:1-40.
4. Carbohydrate supplementation attenuates muscle glycogen loss during acute bouts of resistance exercise. Haff, G.G., Koch, A.J., Potteiger, J.A., et al. International Journal of Sports Nutrition and Exercise Metabolism, 2000; 10[3]: 326-339.
5. Carbohydrate feedings during team sport exercise preserve physical and CNS function. Winnick, J.J., Davis, J.M., Welsh, R.S., et al. Medicine and Science in Sports and Exercise, 2005 Feb;37[2]:306-15.

This story first appeared on Greatist.