Twisted Mountain Climber

Same plank start as a regular mountain climber, but instead of driving your knee straight toward your chest, angle it across your body toward the opposite elbow. That diagonal path is what brings your obliques into the movement instead of just your hip flexors and front core. Keep your hips low and your shoulders square over your hands as you rotate through your midsection rather than your lower back. Alternate sides at a controlled pace — the twist is easy to rush into a half-hearted knee tap, and the rotation is the whole point of choosing this version over the straight one.