Carbohydrates after physical activity

Replenishment of muscle and liver glycogen stores after strenuous exercise is essential to minimizing fatigue. Athletes consuming 7-10 g/kg of carbohydrate per day almost completely replace muscle glycogen stores over the following days.

The timing of carbohydrate intake after exercise also plays a role in glycogen replenishment. Jvy et al. assessed glycogen replenishment after 2 h of vigorous cycling that depleted muscle glycogen.

When 2 g kg of carbohydrate were consumed immediately after exercise, muscle glycogen synthesis was 15.4 mmol kg 2 h after exercise. When the same amount of carbohydrate was delayed for 2 h, muscle glycogen synthesis was reduced by 66% to 5 mmol kg 2 h after exercise. At 4 h after exercise, total muscle glycogen synthesis after the delayed dose was still 45% lower (13.2 mmol kg ) than after the dose consumed immediately after exercise (24.0 mmol kg ).

Liquid and solid carbohydrate products with equal amounts of carbohydrate content taken after exercise result in similar rates of glycogen replenishment. Reed et al. [36] studied the effect of carbohydrate form on glycogen replenishment after exercise. Athletes received 3 g/kg of carbohydrate in liquid or solid form after 2 h of cycling at 60-75% V02max: half the portion immediately after the bike ride and the other half 2 h after it. There was no difference in the rate of muscle glycogen accumulation between the liquid and solid forms at either 2 or 4 h after exercise.

Delaying carbohydrate absorption too long after exercise can reduce carbohydrate storage and impair replenishment. Athletes who are not hungry after exercise can use high-carbohydrate drinks (sports drinks, fruit juices, or commercial high-carbohydrate drinks). This will also help with rehydration.

Athletes who train hard for 90 minutes daily should consume 1.5 g/kg of carbohydrate immediately after training and an additional 1.5 g/kg 2 hours later. The first portion of carbohydrate can be a high-carbohydrate meal. Replenishing muscle glycogen stores after training is especially beneficial for athletes who train hard several times a day.

There are several reasons for faster glycogen replenishment after exercise.

• Blood flow to the muscles is much greater immediately after exercise.
• There is a high probability that the muscle cell will absorb glucose.
• During this period, muscle cells are more sensitive to the effects of insulin, which promotes the synthesis of glycogen.
• Glucose and sucrose are 2 times more effective than fructose in restoring muscle glycogen stores after exercise. Most of the fructose is converted into liver glycogen, while glucose is stored as muscle glycogen.

The type of carbohydrate (liquid or solid) does not affect glycogen replenishment after exercise. Roberts et al. compared the ingestion of simple and complex carbohydrates in both depleted and undepleted glycogen conditions. The researchers found that significant increases in muscle glycogen levels could be achieved with a diet rich in either simple or complex carbohydrates.

The most rapid increase in muscle glycogen stores during the first 24 h of recovery can be achieved by consuming a high glycemic index meal. Burke et al. (40) examined the effect of glycemic index on muscle glycogen replenishment after exercise. A 2-h bicycle ride at 75% V02max was performed to deplete muscle glycogen, followed by a high- or low-glycemic index meal. The total carbohydrate intake over 24 h was 10 g carbohydrate kg 2, distributed equally among meals consumed at 0, 4, 8, and 21 h after exercise. The increase in muscle glycogen stores after 24 h was greater with the high-glycemic index diet (106 mmol kg 2 ) than with the low-glycemic index diet (71.5 mmol kg 2 ).

• Consume 1-4 g/kg carbohydrates 1-4 hours before exercise
• Consume 30-60g of carbohydrates every hour during exercise.
• Consume 1.5 g-kg of carbohydrates immediately after exercise, followed by the same amount 2 hours later.

After unusual physical activity, athletes may experience a decrease in muscle glycogen synthesis, which causes muscle damage. The muscle response to such loads is manifested in a decrease in the synthesis of muscle glycogen and a decrease in its total content in the muscles. While a diet providing 8-10 g of carbohydrates/kg usually replenishes muscle glycogen stores within 24 hours, the damaging effect of unusual physical activity significantly delays its replenishment. Sherman also notes that even normalization of muscle glycogen stores does not guarantee normal muscle function after unusual physical activity.

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