Q&A: Body questions

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I'm still sore three days after a long run. Is that okay?

If it’s not sharp, localised pain – which could indicate an injury – it’s probably delayed-onset muscle soreness (DOMS), which can peak two days after a hard workout and linger even longer. However, spend the next day or two recovering with short, slow runs, easy swimming or cycling sessions, or rest. Applying heat, stretching post-exercise, getting a light massage and wearing compression socks may also help ease soreness.

Tracy Golder, marathoner and online coach

Why do my knees brush together while I'm running?

The contact may be a symptom of muscle imbalances or flexibility problems. To reduce injury risk, strengthen your hips and glutes, stretch your inner thighs and ankles, and make sure your shoes are right for you and are not too old.

Danelle Ballengee, running coach

What slows me down more, my muscles or my breathing?

Both play a role, although the respiratory system limits your performance most when you’re sprinting or charging up a steep hill. Practise this fast-as-you-can-go running, your breathing and heart rate get close to their limit, and you’re forced to go ‘anaerobic’ (that is, to produce energy in the absence of sufficient oxygen). For all other kinds of running, the main limiting factor is muscle fatigue. Fatigue begins in the muscles during all aerobic [not all-out] running as your stored muscle glycogen and glucose are depleted. Your brain will apply the brakes before too much damage occurs. In the end, your mind – in concert with your body – will force you to slow down, no matter how determined you are.

Christopher Minson, professor of human physiology at the University of Oregon, US