We spoke with people on every side of the issue: the ones who started it, the ones affected by it and a few who are still not convinced.

Heat changes everything here. Hydrate early and plan activity for the cooler parts of the day.

The numbers

Start smaller than you think you should. Consistency matters far more than intensity in the first month.

Heat changes everything here. Hydrate early and plan activity for the cooler parts of the day.

A few years ago this would have sounded unusual. Today it is ordinary enough that most people do not think about it at all.