Knee Drivers Bend your left knee and extend your right leg behind you, placing little to no weight in the right toes. Raise both hands straight above your head. Drive your right knee up toward your chest, bringing your hands down to meet it. Reextend the right leg behind you as you lift your arms back up. Continue for 20 seconds on this leg, then switch sides for the remaining 20 seconds. Image Source: POPSUGAR Photography