I have enjoyed relaxing in the sauna, especially in cold weather, for many years. But last summer, I was surprised to see a doctor friend emerging from the sauna in the sweltering heat of July on his way to a workout, dripping from sweat before he even reached the gym.

The doctor explained that as we get older, it becomes increasingly important to warm our muscles, tendons and joints before undertaking strenuous physical exercise. While a 10-minute warm-up on a stationary bike or treadmill might be the traditional way to gently warm muscles, the sauna really heats them up and gets them ready for exercise.

This struck a chord with me because for the past few years, I have suffered agonies from an Achilles tendon problem every time I run. I have been treated by a number of doctors, who have prescribed stretching, heel inserts in my trainers and even used sound waves to bombard my Achilles tendon — all without much lasting effect.