In today’s fast-evolving fitness world, trends come and go—but some classics are proving their lasting value. The stair climber, once overlooked in favor of treadmills and bikes, is now regaining ...

OK, what is a calorie, anyway? It’s a unit of energy, defined as the amount of energy needed to raise the temperature of 1 liter of water by 1 degree Celsius. (This is your common “food calorie”: ...