Break a Sweat With 17 Quiet, Bodyweight Cardio Moves That Won't Annoy Your Neighbors

Want to make mountain climbers more of a challenge? Get creative with your knee placement, Rademacher said. "Add in a crossbody rotation by bringing the right knee to the left elbow. Or, optionally, bring the right knee to the outside of the right elbow for a challenging low core and hip mobility exercise." You can do one variation at a time or combine them as shown below.

• Start in a traditional plank — shoulders over hands and weight on your toes.
• With your core engaged, twist to bring your right knee forward under to your left elbow, then bring that same knee to your right elbow to work your obliques and come back to plank.
• Repeat this with your left knee for one rep.