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Chris - 32 years old


Chris Broad, 32 years old, Ironman specialist, Sheffield

“Three and a half miles swimming, 120 cycling and a full marathon. You’d better be sure the muscles are in perfect condition as well as the mind! You get years of training in the legs, heart and lungs. But you also have to be careful what you eat and when. Training and diet are linked.

Sometimes you don't eat enough carbs, and you feel it in training. You get tired fast, but you force the muscles to go on. Then you put the carbs in again and you feel the strength flow back as the glucose and muscle glycogen levels build up. After that, it’s all a question of what you eat in the days before the event, and what and when you eat and drink to maintain body fuel during it, without overloading the system.

Your first triathlon, you get personal satisfaction even if you don’t finish in the first hundred. But if you want to get near the top, you have to see it as a science as much as a sport.”


Energy needs of endurance athletes

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As athletes are focusing on achieving maximum performance, they treat their body like a high-performance engine. Nutrition is carefully planned and thought through.

Maintaining energy balance is a key goal for athletes. Balance occurs when total energy intake from food matches energy expenditure from daily activity. Many athletes are faced with the challenge of achieving very high energy intakes to support extremely high training loads. Depending on intensity and duration of exercise, an athlete may regularly expend twice as much energy as a sedentary person. Furthermore, many sports are performed in environments that can increase energy expenditures (cold, humidity, altitude). Consequently, sporting activities can involve additional energy expenditure ranging from around 1,000 kilocalories/day (dancing, martial arts) to as much as 7,000 kilocalories/day (long-distance cycle races, endurance treks).

Energy for contraction and work mainly comes from the metabolism of sugars and fats. The basic fuels supplying muscles are: glucose transported from the liver in the bloodstream, glycogens stored locally in muscles and free fatty acids. All these come from the diet. The contribution of each fuel to total muscle output varies with intensity and duration of exercise, state of fitness and nutritional status before and during exercise.

During prolonged, aerobic exercise, energy is provided by the muscle glycogen stores – which directly depend on the amount of carbohydrates ingested. This is not the only reason why dietary carbohydrates play a crucial role in athletic performance; they have also been found to prevent the onset of early muscle fatigue and hypoglycaemia during exercise. By keeping carbohydrate intake high, an athlete therefore replenishes his glycogen energy stores, and reduces the risk of rapid fatigue and a decline in performance. At the same time, carbohydrate intake should not be so high as to drastically reduce the intake of fat, because the body will use fat as a substrate once glycogen stores are depleted.

The use of body protein in exercise is usually small, but prolonged exercise in extreme sports can degrade muscle, hence the need for amino acids during the recovery phase.

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