“I want you to go to failure,” says my personal fitness trainer as my heart rate swoops upward, and I grunt my way through the fifth rep of single leg walkouts. For the uninitiated: a single leg walkout consists of squatting, leaning over to walkout to a plank with my hands, do a pushup or hold the plank, then walk myself back to squatting and then standing up while pushing through my heel, ALL ON ONE LEG (see video below). I can modify this exercise so that 60% of my weight is on the side I’m working on, and 40% is on the other leg. I am absolutely not able to do this without my other leg sharing the load, at least not yet (I watched someone he was training do this all on one leg, so I know it’s possible). As he introduces each knew exercise into the day’s routine, he says he wants me to grunt, to fail, to push when my muscles are burning, until I cannot move that way anymore in that moment. This way of exercise is exhausting, and maybe a little intimidating.