When the fitness company Peloton added weighted-vest classes to its streaming exercise offerings in May 2025, its members rejoiced, says instructor Rebecca Kennedy. “They were like, ‘Finally! You answered my prayers’!” she laughs. “The appetite has been really wild.” Strapping extra weight to your body while working out is nothing new; the practice of “rucking” —walking with a weighted backpack—has roots in military training and has been shown to help improve endurance and build muscle power