Then, according to the BBC, in 2014 and 2018, HIIT came top of the American College ... participants who performed 20-minute HIIT workouts 4 days a week for 5 weeks improved their oxygen ...
Bottom line: I feel like I was happier to do the ab workout—and I put in more effort—on the days it followed runs, hikes, and cycling sessions. And FYI, if you’re wondering how to best ...