Recently, there’s been a surge in the popularity of workout programs like Bodypump, P90x, and ClassPass, all of which are based on “muscle confusion,” or the premise that constantly switching up your workout routine — i.e., “confusing” your muscles — is the pathway to fitness gains. It’s an enticing idea, as evidenced by the numbers: Since 2004, P90x has sold five million copies, and last year alone, ClassPass brought in over $60 million in revenue. Unfortunately, muscle confusion doesn’t work.
“All the crap you hear about your body needing a different stimulus each week or a new ‘workout of the day’ is garbage,” says Brett Bartholomew, CSCS*D, director of performance at Unbreakable, a Los Angeles gym that Yahoo called the most elite gym in America. “The number-one reason people don’t get results is that they don’t have the attention span to stick with something.” (At the Cut, Kathleen Hou once wrote that ClassPass is like “being in an open relationship with exercise.”)
Bartholomew, who coaches a stable of professional athletes, including last year’s Super Bowl MVP, Vonn Miller, told me that the key to getting fitter lies in adhering to something called “progressive overload.” And, years of exercise science support his assertion. Citing increases in strength and muscle size, the American College of Sports Medicine (ACSM) published an official-position paper in favor of progressive overload for resistance training in healthy adults, and a 2015 study published in the journal Frontiers in Physiology found that the best endurance athletes in the world follow progressive overload’s principles.