The Importance of Carbohydrates in Sport: Training and Performance

Over the years, carbohydrates have often been in the spotlight as a dietary villain.

Since the introduction in 1972 of the Atkins Diet, a low-carbohydrate fad diet, there has been confusion regarding the role of carbohydrates in the modern diet. Are they healthy for us, or are they indeed as fattening as some diet books may have led us to believe?

Recreational and elite athletes are not immune to persistent low-carbohydrate messaging, and there are questions surrounding whether or not this type of restrictive diet hinders training and performance.

What are Carbohydrates?

Carbohydrates are the primary fuel source for our body, particularly for our brain and blood cells, and are especially important during physical activity. Common dietary sources of carbohydrates include fruits (fresh, frozen, dried), starchy vegetables (potatoes, peas, corn, squash), grains (bread, pasta, rice, cereal, quinoa, barley), pulses (lentils, chickpeas, beans), and dairy products.

Carbohydrate-containing foods are rich sources of fiber, vitamins, and minerals like magnesium, potassium, calcium, iron, B vitamins, and vitamin C. Carbohydrates assist with the preservation of muscle mass, since our body would instead break down protein as an energy source in their absence. In addition, they help maintain our gut health by increasing dietary fibre to allow for normal bowel movements and also provide our gut microorganisms with a source of non-digestible fiber that they can break down and ferment.

The Importance of Carbohydrates in Sport: Training and Performance

Any recreational or elite athlete who wants to train faster, harder or longer will need to consume carbohydrates in their diet. When we eat carbohydrates during a meal or snack, they are stored as glycogen (the storage form of carbohydrates) in the muscle and liver. During intense intermittent activity (such as soccer or hockey) or endurance exercise, the body breaks down these sugar stores to free glucose molecules so that muscle cells can use them for energy. An individual’s daily carbohydrate requirement should match their fuel needs for training. Without providing your body with enough carbohydrates each day or allowing enough time to refuel depleted glycogen stores, you would run out of energy faster and exercise would feel harder. Lack of carbohydrates can lead to a reduction in exercise intensity and muscle power.

Do carbohydrates cause weight gain?

Some have argued that carbohydrates cause weight gain, but where is this additional weight really coming from? When we look at our physiology, we find that each glycogen particle in the liver can be 10 times larger than a glycogen particle in a muscle cell. Additionally, each gram of glycogen is stored with at least 3 grams of water, which results in water weight gain when athletes consume large amounts of carbohydrates. When we follow a low-carbohydrate diet, rapid weight loss occurs as glycogen is broken down and water is released as urine. When we add carbohydrates back into our meals, the weight loss is reversed as glycogen stores are restored and water is retained. Furthermore, low-carbohydrate diets can be detrimental to our health. For example, they have been linked to various nutrient deficiencies. These diets are also difficult to follow over the long term for the majority of people, often leading to weight regain, termed the “yo-yo effect.”

For Endurance and Intermittent Performance: Eat Carbohydrates

Beginning exercise with adequate muscle glycogen stores is important for enhancing exercise performance. It is also important to consume carbohydrates during and following endurance and intermittent exercise. During endurance exercise (cycling, running/jogging, hiking), the amount of glycogen in muscles declines, leading to fatigue, as muscle cells are unable to produce enough energy to maintain the intensity level. Consuming a source of simple carbohydrates (i.e., glucose, fructose, maltodextrin) during exercise that is 1–1.5 hours or longer raises blood glucose levels, providing a quick source of energy for the working muscle that can delay fatigue and improve performance.

For intermittent sports, consuming carbohydrates during the activity positively affects the central nervous system, which may enhance sprinting and skill performance in some sports. Immediately after physical activity, muscle cells that have been depleted of their glycogen stores are now ready to receive carbohydrates. Immediate intake of carbohydrates after exercise results in a slight increase in the rate of glycogen synthesis, which helps to restore levels faster and prepare you for your next exercise session!

For muscle Growth: Eat Carbohydrates

Studies have shown that you use a lot of carbohydrates when you lift weights, with some indicating that you may use 30%–40% of your glycogen stores during a single resistance training session. The amount of carbohydrates used in a training session appears to be related to the amount of repetitions, the load used, and the duration of the workout. Consuming enough carbohydrates along with adequate protein intake may enhance protein synthesis, decrease muscle breakdown, and ultimately enhance the effects of resistance training.

Takeaways

Carbohydrates should be included in your diet, whether you are a recreational athlete, a “weekend warrior” or an elite athlete. For endurance and intermittent team sports, carbohydrate consumption during exercise is beneficial.

Examples of carbohydrates that athletes commonly consume during exercise include sports gels, sports drinks, dried dates, and bananas. Consuming carbohydrates after exercise, along with protein and adequate fluid, can assist in the body’s recovery process. Common post-exercise snacks include a sandwich, a piece of fruit with nuts or Greek yogurt, or a fruit smoothie with protein powder.

References

Baker, L.B., Rollo, I., Stein, K.W., & Jeukendrup, A.E. Acute effects of carbohydrate supplementation on intermittent team sports. Nutrients. 2015; 7(7):5733-5763.

Haff GG, Koch AJ, Potteiger JA, et al. Carbohydrate supplementation attenuates muscle glycogen loss during acute bouts of resistance exercise. Int J Sport Nutr Exerc Metab. 2000;10(3):326-39.

Haff GG, Lehmkuhl MJ, McCoy LB, et al. Carbohydrate supplementation and resistance training. J Strength Cond Res. 2003;17(1):187-96.

Jeukendrup A. Carbohydrate supplementation during exercise: Does it help? How much is too much? Sports Science Exchange. 2007;20(3). Available at: https://www.gssiweb.org/en/sports-science-exchange/Article/sse-106-carbohydrate-supplementation-during-exercise-does-it-help-how-much-is-too-much-.

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Murray B, Rosenbloom C. Fundamentals of glycogen metabolism for coaches and athletes. Nutr Rev. 2018;76(4):243-259.