Recovery

Training is only the stimulus – you get stronger during the recovery that follows. Exercise causes tiny damage to muscle fibres, energy stores run low and the nervous system tires. During recovery, the body doesn't just repair all this, it builds up a little more than before. Sports scientists call this supercompensation.

How long it takes depends on the load: after a gentle walk you've recovered within hours, after intense strength training the muscles involved need around 48 hours, and after a competition it can take several days. That's why it's smart to alternate strength and endurance days and to plan at least one completely restful day each week.

The most important building block is sleep. The US National Sleep Foundation (NSF) recommends 7 to 9 hours for adults, 8 to 10 for teenagers and 9 to 11 hours for school-age children. During deep sleep, the body releases growth hormone, which repairs muscles and tissue. If you sleep too little, you'll be hungrier, have less strength and face a higher risk of injury.

Then there's food and drink: protein provides building blocks for muscles, carbohydrates refill the stores and water replaces sweat. If you're trying to lose weight, the deficit should stay moderate (around 300 to 500 kilocalories a day); otherwise your body lacks the energy for repairs.

Active recovery – a walk, an easy bike ride, swimming, gentle stretching – boosts circulation and often does more good than lying still. Warning signs of too little recovery are a raised resting heart rate, poor sleep, irritability and performance that drops despite training. When that happens, take an easy week instead of training even harder.