Resistance training by the numbers

Resistance training (also known as strength training) consists of doing upper- and lower-body exercises using free weights (like dumbbells, kettlebells, or barbells), weight machines, resistance bands, or even body weight. It is regarded as one of the best ways to slow and even reverse age-related muscle loss, known as sarcopenia. The constant challenge with resistance training is finding that happy medium between doing too little and too much. New guidelines suggest people should focus on five categories: type of exercise, reps, weight, sets, and frequency.