Both ends of the thermometer

Heat and cold, on purpose, as part of training rather than a treat after it. We call it both ends of the thermometer, and it is the bit most people skim past.

Most of us do one or the other. The sauna crowd sweat and never go near cold water. The cold-water crowd stand in the sea in January and would not be seen in a sauna. We believe they are two halves of the same thing, and the half you avoid is the half you need.

Heat makes you sweat and makes your heart work as if you were walking uphill, and it does it while you sit still. Cold does the opposite. It shocks, it narrows everything, it slams the body into alertness, and then when you get out the blood comes back and you feel more awake than coffee has ever made you.

Then there is the part that matters more than the physiology. Getting into cold water at half past six in the morning when you do not want to is a decision, and making that decision every day is training for every other hard decision you will make before bed. The body gets a little tougher and the head gets a lot tougher.