Plank jack

Hold a high plank and hop your feet out and in like a jumping jack, raising your heart rate while working your core and shoulders.

How to do it

1. 01Start in a high plank with hands under your shoulders, feet together and body straight from head to heels.
2. 02Brace your abs and glutes and push the floor away so your shoulders do not sink.
3. 03Hop your feet out wide and back together, landing lightly on the balls of your feet.
4. 04Keep your hips still and level with your shoulders for the full interval, breathing steadily.
5. 05For a gentler version, step one foot out and back at a time instead of hopping.

Common mistakes

• Hips bouncing with the feet — brace so only your legs move.
• Shoulders drifting behind the wrists — keep them stacked over your hands.
• Slamming the feet down — hop lightly at a moderate pace, or switch to stepping.