Sit-ups

1. 1Lie on your back with knees bent, feet flat and about hip width apart. Cross your arms on your chest or rest your fingertips by your ears without pulling on your head.
2. 2Press your lower back lightly into the floor and exhale as you curl up, peeling your head and shoulders off first, then your mid back, until your chest is close to your thighs.
3. 3Keep your chin a fist width from your chest and your feet down. If your heels lift, slide them closer to your hips or hook them under something solid.
4. 4Inhale as you lower, laying your spine down one section at a time rather than dropping in one piece.
5. 5Touch your shoulders lightly to the floor and begin the next curl without resting, keeping the same speed for the whole effort. When the range starts to shorten, slow down instead of yanking.

• Pulling on the back of the head with the hands, which cranks the neck forward.

  →Fix: Rest the fingertips at the ears and lead with the chest, so the neck stays in line with the spine.

• Throwing the arms and bouncing off the floor to gain momentum.

  →Fix: Pause for a beat at the bottom and start each curl from a still position.

• Hinging straight up from the hips with a flat back, so the abs barely work.

  →Fix: Round the spine deliberately: think of curling your ribs toward your hips before you rise.

None of the fixed workouts uses it. Pick a workout for your kit, or start today's session on /gym.