Most people would rather stub their toe than get into a tub of ice. But it's worth it. We all know ice can reduce inflammation and lessen joint pain, and that it feels good on sore muscles. But extreme drops in body temperature – in an ice bath or a cold shower – are like another form of exercise that burns calories and fat, gives focus, and can lower your heart rate.

Starting Out
I like to make ice baths part of an exercise circuit. First, I'll lift or swim at a rate of high exertion, then I go straight into the ice, up to the neck. I go right back to the activity, then into the ice, and repeat a few times. Thermal regulation is an extremely energy-consuming process in our body, meaning this circuit requires an enormous amount of effort – and will leave you exhausted. If you don't have an ice tub in your gym, look for an outside body of water in cold months, or fill an ice bath and get in immediately following your workout.

Running Cold
It'll take some time to build up the stamina for a full-body ice bath. You should start with cold showers. I always take one after a workout to stop sweating. Once you're able to handle a really cold shower, dump a bag of ice in the bathtub and get in. As you build up tolerance, focus on your breath, distract yourself with music, and keep a clock nearby to watch your progress. If you're still struggling to stay in, try it in the morning – your tolerance is a lot lower later in the day because your body is tired and not prepared for the shock.

The Other Benefits of Ice
People have the big misconception that if you are exposed to cold, you store fat, but you actually burn fat unbelievably well at lower temperatures. Studies have shown that prolonged exposure to cold can activate brown fat, which will help burn the white fat in your body, helping to keep you slim.