Start in a push-up position, body straight from head to heels. Step one foot forward and plant it beside your hands, then lift your hands off the floor and raise your torso into a low runner's lunge - hands coming together in front of your chest, back leg staying long and strong behind you. Place your hands back down, step the foot back to the plank, and repeat on the other side. Stay low through the whole cycle: it's a flow between two strong positions, not a stand-up.

Works: abs, hip flexors, glutes, quads, shoulders

Breathing: Exhale as you step in and rise into the lunge, inhale as you return to the plank.

Common Mistakes: Landing the foot short of the hands so the step becomes a shuffle, popping the torso up tall instead of holding the low lunge, and letting the hips sag once back in the plank.

Make Easier: Keep your hands on the floor throughout and just work the step, or slide the foot in stages - or build up with Slow Climbers first.

Make Harder: Hold the low lunge for a beat with the back leg squeezing straight, or move on to Plank Jump-Ins or Burpees.