For the final 15 seconds, sit up holding a medicine ball with both hands. Lower your torso back, so that you are in a V-sit position and can feel your abs working hard.

Less sit-ups, more compound ... If you’re performing these from home without a rower, you can use alternatives, including sliders, a medicine ball, or even a dish towel.

Bring your hands and feet together and pass the ball from your hands to your feet and lower your arms and legs again to complete the rep. Aim for 20 reps in total, says Mounsey-Jennings. 5.

The singer/actor has decided to get himself in shape for the tour by doing L-sit ring chin-ups with a weighted vest and a medicine ball. I may be exhausted watching him, but I’m also impressed ...