Start in a plank position with your feet together and your body in a straight line. Step one foot out to the side and plant it, then step it back in to meet the other. Now step the other foot out and bring it back in. Out, in, out, in, alternating sides for the whole set. Your hips stay level and your shoulders stay quietly over your hands while your feet do all the traveling.

Works: abs, glutes, hip abductors, shoulders

Breathing: Exhale as the foot steps out, inhale as it comes back in - slow and even.

Common Mistakes: Letting the hips swing toward the stepping foot, piking up as the leg reaches out, and rushing the pattern until the steps blur into shuffles.

Make Easier: Take smaller steps and pause in the plank between reps, or drop to a forearm plank for a steadier base.

Make Harder: Slow every step to a deliberate two-count, or add the jump with Plank Jacks or Plank Jump-Ins.