Editor’s Note: A few weeks ago, Dr. Mirkin wrote about how to improve endurance performance through proper nutrition and hydration. Today, he focuses on the benefits of proper nutrition during and after intense exercise.
By Gabe Mirkin, M.D.
Eating during and after long, intense workouts helps competitive bicycle racers recover faster from their workouts and therefore helps to make them stronger and faster. It is the intense workout that makes you stronger and faster, so the more rapidly you recover from an intense workout, the sooner you can take your next intense workout, and the more improvement you will gain.
If you want to improve your athletic ability to become faster and stronger and to have more endurance, you need to train in a program of stress-and-recover. You must exercise vigorously enough to feel burning, a sign of muscle damage, so that when muscles heal, they will be larger and stronger.
To increase your ability to move faster over distance, you have to exercise vigorously enough to become short of breath. However, eight to 24 hours after you take an intense workout, your muscles are sore because they are damaged. If you try to exercise vigorously when your muscles are sore, you are at high risk for injury, which could mean that you will not be able to exercise at all.
So all athletes learn sooner or later that on one day, they have to take an intense workout that damages their muscles, and on the next day or as long as their muscles feel sore, they need to go at a reduced intensity. When their muscles feel fresh again, they take their next intense workout.
DOMS, the soreness you feel four to 24 hours after a hard workout, is caused by: using up the sugar, called glycogen, that is stored in meager amounts in muscles; and damage to the muscle fibers themselves.
Taking carbohydrates (sugar) both during and immediately after vigorous exercise replaces your used-up glycogen. Protein provides the building blocks to help muscle fibers heal (Current Sports Medicine Reports, July/August 2015;14(4): 294–300).
A resting muscle takes up almost no sugar, and the small amount that may enter the muscle requires insulin to move the sugar from the bloodstream into the muscle cells. However, contracting muscles are an entirely different story. When a muscle contracts, it takes up large amounts of sugar and protein from the bloodstream and it does not need any insulin to do so.
The effect of being able to take up sugar and protein without needing insulin is maximal in muscles during exercise and for up to an hour afterward, and fades quickly after that. Therefore, to help your muscles recover at their most rapid rate, you should take something to eat within the first hour after you finish exercising. After that, muscles take up sugar at a much slower rate, require more insulin to do so, and it takes longer for your muscles to recover.
If you are in events that require consecutive days of riding, you will recover much faster by eating any source of sugar and protein immediately after finishing your first competition or day on the bike. In training, you will recover faster from your hard workout by eating immediately afterward. Snacking throughout the day also helps muscles to recover faster.
Taking sugar while you ride increases the amount of riding you can do, and does not lessen the benefits of your increased training. For a study in the Journal of Applied Physiology (June 2009), bicyclists trained for two hours a day, five days a week. On one day, they trained one leg while ingesting a 6 percent sugar drink, and on the next day they trained the other leg while taking an artificially sweetened (sugarless) drink. The legs trained with sugar had 14 percent more power and a 30 percent greater time to exhaustion.
Athletes in sports requiring endurance and speed need to train in their sport many hours each day. The more intense the stress-training workout without injury, the more intensely they can compete. Intense exercise requires muscle sugar (glycogen) as its principal source of energy (J. Physiol, 2001; 536: 295–304).
In 1967, Jonas Bergstrom showed that you have only a meager amount of sugar stored in muscles, and once you run out of stored muscle sugar, your muscles hurt, you feel tired, you lose power, and you have to slow down (Acta Physiol, Scand. 1967; 71: 140–50). In cycling, this is typically referred to as “bonking.”
Anything that preserves stored sugar in muscles during a workout will help you exercise longer. This study shows that taking sugar regularly during intense workouts allows you to extend the amount of training without lessening the benefits that you receive from the extra work.
The question had been asked whether restricting sugar during training could enhance performance by teaching the muscles to get along with less sugar. The alternate-leg-training study's authors showed that the enzymes used to convert sugar and fat to energy function just as well when sugar is taken continuously during exercise training (Journal of Applied Physiology, June 2009). The muscles trained on sugar had no loss in the amount of stored sugar or the ability to convert food to energy.
Another study showed that taking a drink containing both protein and sugar every three miles and at the finish of a 36-mile bicycle time trial was far more effective than a drink containing just sugar in terms of: 1) riding faster at the end of the time trial, 2) preventing next-day muscle soreness and 3) lessening muscle damage, as measured by a blood test called CPK (International Journal of Sport Nutrition and Exercise Metabolism, April 2009). A protein-sugar drink taken immediately after intense exercise also hastens healing of the muscles damaged by hard exercise (Journal of Applied Physiology, April 2009).
However, taking extra refined carbohydrates (sugar or flour) when you are not exercising can cause a high rise in blood sugar that increases risk for weight gain, diabetes and heart attacks. Contracting muscles remove sugar so fast from the bloodstream that blood sugar usually does not rise too high during exercise and for up to half an hour after you finish exercising. However, you do not have this benefit during or after casual exercise or on days off.
Most people do not need to eat when they exercise at a relaxed pace for less than two hours. On the other hand, you will start to run out of stored muscle sugar at about 70 minutes of intense bicycle riding. Before and during intense rides lasting longer than 70 minutes, you should eat any source of sugar: a sugared drink, fruit, chocolate bars, candy or anything else you like. You do not need to spend extra money on sports supplements as you can get all the sugar you need from other foods, and you do not need to replace any other nutrients.
In competitions lasting more than two and a half hours, you should also eat any food that provides some protein, such as nuts or a sandwich. In competitions lasting more than three hours or in very hot weather, you also need to replace the salt you lose in sweat. The easiest way to get salt is with potato chips, salted nuts, French fries or whatever salty foods taste good to you.
You are unlikely to be able to get enough salt in a sports drink because salty drinks taste awful (and sports drink makers thus do not use enough salt in most of their commercial drinks). You do not need to replace any other mineral or vitamin during exercise, so you do not need to take sports drinks or supplements containing calcium, potassium or magnesium.
Caution: Exercising intensely is more likely to cause injuries and can cause heart attacks in people with blocked arteries leading to their hearts. Check with your doctor. People who suffer heart attacks during exercise are usually just starting an exercise program or making a sudden increase in the intensity or duration of their exercise. If you have not been training regularly, get in shape gradually by exercising at an easy pace three to six days a week for at least six weeks.