This high-efficiency workout style boosts heart health, builds lean muscle, and transforms your fitness routine — all without a gym.

Fitness is always top of mind this time of year, as many athletes begin to fine-tune their disciplines and many casual exercisers re-up their commitment as part of their resolutions for the new year.

Think you always need long, slow strength sessions to build strength and burn fat? Think again. New research suggests that high-intensity circuit training—workouts that pack multiple strength moves ...