To accomplish that, she recommends doing short intervals at a sprint pace. " could be running, rowing, biking or doing other kinds of exercises -- such as burpees, squats or even push-ups," she says. "Whatever , you’ll know you’ve increased the intensity when you're out of breath and feel that good burning sensation in whatever muscles are being worked." Cutting your recovery time and pushing yourself during a workout are great steps toward having more stamina, but don't forget that your body still deserves some R&R.