Muscles worked
In the lying leg raise, your hip flexors lift your legs. Your abs have a different job: holding your pelvis still and your lower back on the floor while the weight of your legs pulls the other way. That job is hardest when your legs are near the floor and almost vanishes when they point straight up. It therefore pairs well with exercises where your abs curl the spine. Bending your knees shortens the lever and makes the lift easier.
Common mistakes
- Your legs drop. Letting gravity handle the lowering skips the part where your abs work hardest. Take two to three seconds on the way down and turn without bouncing.
- You rest with your legs straight up. Pointing at the ceiling, your legs nearly balance on their own above your hips and the tension fades. Turn just before vertical, or lift your bum slightly off the floor at the top to give your abs more work.
- You lift your head to watch your feet. That tenses your neck and shoulders without helping your abs. Keep the back of your head on the floor.
Variations and alternatives
- The dead bug is an easier way to practise keeping your lower back down while your legs move.
- The reverse crunch uses bent knees and curls the pelvis up, giving your abs more of the work.
- Flutter kicks keep your legs low for the whole set with small kicks and suit endurance work.
- The hanging leg raise moves the same lift to a bar and is a clear step up.
Sets and reps
Three sets of 8 to 15 reps are a sound starting point, each with an unhurried lowering. If your lower back will not stay down all the way, bend your knees or turn higher up, and widen the range over time. The guide to sets and reps covers choosing reps and sets.
Raise the difficulty in this order: straighter legs, slower lowering, turning closer to the floor and finally ankle weights. This is called progressive overload. If your lower back or groin feels painful rather than tired, stop and have it looked at by a doctor or physiotherapist.