The Athlete's Recovery Drink
A 16-year-old athlete runs a 10 km race in 45 minutes. Before the race, she eats a breakfast of white toast with jam and a glass of orange juice. During the race, she drinks 500 cm³ of a sports drink containing 6% glucose and electrolytes. After the race, she feels tired and has muscle cramps. Her coach suggests she eat a banana and drink water. A friend says she should take a protein shake immediately because 'protein builds muscle'. The athlete wants to know which advice is best for recovery and why. The sports drink label says it contains 30 g of glucose per 500 cm³.
1. Explain why the athlete felt tired after the race and why the sports drink during the race may have helped. Use your knowledge of respiration and digestion.
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During the race, muscles respire aerobically using glucose from the breakdown of glycogen stored in the liver and muscles. The breakfast toast and jam provided carbohydrates, which are digested to glucose and absorbed into the blood. However, 45 minutes of intense exercise uses glucose faster than it can be replaced from stores, so blood glucose may fall. The sports drink contains 30 g of glucose in 500 cm³, which is absorbed quickly from the small intestine into the blood, supplying muscles with glucose for respiration. Without enough glucose, muscles respire anaerobically, producing lactic acid and releasing less energy per glucose molecule. Lactic acid builds up and causes fatigue and cramps. The electrolytes in the drink help replace salts lost in sweat. So the drink helps by providing glucose and fluids, delaying fatigue.
2. Evaluate the coach's advice (banana and water) and the friend's advice (protein shake immediately) for recovery after the race. Which is better and why?
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The coach's advice is better. After exercise, the body needs to replace glycogen stores and rehydrate. A banana contains carbohydrates (starch and sugars) that are digested to glucose, which is absorbed and used to replace glycogen in muscles and the liver. Water replaces fluid lost in sweat. The friend's advice is less suitable immediately after the race because protein is not the main fuel for energy; it is used for growth and repair. Protein digestion is slower, and a protein shake does not quickly restore blood glucose or glycogen. While protein is useful later for muscle repair, the immediate need is carbohydrate and water. Therefore, the banana and water are better for fast recovery. The sports drink during the race also helped, but after the race, solid food with water is effective.