Mountain Climbers 1. Start in plank position, hands directly underneath your shoulders, elbows locked, abs tight and engaged, glutes squeezed, knees and feet together. 2. Raise one knee up, bent in towards your chest with the ball of the foot planted on the ground. 3. Jump and switch the position of the legs while you’re still in the air. Focus on keeping the body straight and in that tight plank position throughout.