Why warm up muscles?

Katie Haylor put this steamy question to Cambridge University's Christof Schwiening.

Christof - Muscles get warm when the contract repetitively, like when you’re running, cycling, or skipping. Yoga produces relatively little heat and the temperature of most muscles will be close to that of your core body temperature whether you’re in a normal room or in one heated to 40 degrees celsius. Scientific investigations into hot yoga provide little evidence that it is much different from normal yoga.

However, passive heating can improve health and make you aerobically fitter. For instance, saunas can produce cardiovascular, skin, and mental health benefits. It is possible that hot yoga may produce some of these effects.

Katie - That’s the “hot” part of hot yoga sorted. What about warming up muscles before a class? What’s going on at a cellular level to make this a good idea?

Christof - The warmer the muscle is, the more force it can produce. The evidence for that is very clear. So if you want to run a fast, short race where maximum power output is needed, you should warm up first.

But warming up is about more than just getting a muscle warm: it’s about increasing blood flow to the muscles and increasing the amount of blood being pumped by the heart. Warming up muscles also changes your general physiology, from the control of blood flow, hormonal background, mental state, neuronal pathways, and energy supply.

As far as yoga is concerned, the main benefit of warming up using movement rather than simple passive heating may well be the changes in neuronal activation. Warming up may well help to relax muscles that would otherwise be partially contracted. It is true that warming can produce small and transient increases in muscle flexibility, but the current view is that it is the training of our nervous systems that produces the biggest improvement in range of motion.