Alternate Straight Leg Raise (on bosu ball)
- Target muscle
- Iliopsoas, Rectus Abdominis
- Synergist muscles
- Adductor Brevis, Adductor Longus, Obliques, Pectineous, Quadriceps, Sartorius, Tensor Fasciae Latae
- Equipment
- Bosu ball
- Body part
- Waist
- Type
- Strength
The alternate straight leg raise on a bosu ball is a bodyweight core exercise that targets the hip flexors (iliopsoas) and the rectus abdominis. Lying back on the dome of the bosu ball, you lift one straight leg at a time while the unstable surface recruits the obliques, quadriceps, adductors, sartorius, pectineus and tensor fasciae latae to keep you balanced. It builds lower-ab and hip-flexor strength while training anti-rotation core control.
How to do the Alternate Straight Leg Raise (on bosu ball)
- 1Sit on the dome of the bosu ball and lie back so your lower back and hips are supported on the curved surface, with your head and shoulders relaxed.
- 2Extend both legs out straight along the floor and place your hands at your sides or lightly on the bosu for stability.
- 3Brace your core and press your lower back gently into the dome to lock in a stable, neutral position.
- 4Keeping the leg straight, raise one leg upward until it points toward the ceiling, leading with the heel.
- 5Pause briefly at the top while keeping your hips level and the opposite leg extended on the floor.
- 6Lower the leg under control back to the starting position without letting it drop or your back arch.
- 7Repeat with the opposite leg, alternating sides for the prescribed reps.
- 8Finish by lowering both legs, then carefully sit up and step off the bosu ball.
Form tips
- Keep both legs fully straight throughout so the iliopsoas and rectus abdominis do the work rather than bent-knee momentum.
- Move slowly and deliberately — the unstable bosu surface rewards control and punishes jerky reps.
- Keep your hips square and level as each leg rises so the obliques resist rotation.
- Exhale as you lift the leg and keep your core braced to protect your lower back.
- Start with a smaller range of motion until you are confident balancing on the dome.
Common mistakes
- Arching the lower back off the dome as the leg rises, which shifts strain to the spine instead of the abs.
- Bending the knee to swing the leg up, which uses momentum and reduces tension on the hip flexors and abs.
- Letting the hips rock or tilt side to side, which wastes the anti-rotation benefit and can throw off your balance.
- Dropping the leg quickly on the way down instead of lowering it under control, losing the eccentric work.
- Holding your breath, which raises tension and makes it harder to stay balanced on the unstable surface.
Frequently asked questions
What muscles does the alternate straight leg raise on a bosu ball work?
It primarily targets the iliopsoas (hip flexors) and the rectus abdominis, with the obliques, quadriceps, adductors, sartorius, pectineus and tensor fasciae latae assisting and stabilizing on the unstable surface.
Why use a bosu ball instead of the floor?
The bosu's unstable dome forces your core to work harder to balance and resist rotation, recruiting the obliques and hip stabilizers more than a flat-floor leg raise does.
Is this exercise good for beginners?
Yes, but balance comes first. Start with a small range of motion and slow tempo, and bend the knees slightly if keeping the legs fully straight strains your lower back until your core strength improves.
How many sets and reps should I do?
Aim for 2–3 sets of 8–12 reps per leg, focusing on slow, controlled movement rather than speed or high numbers.
Where should I feel this exercise?
You should feel it in your lower abs and the front of your hips (the hip flexors). If you feel it mainly in your lower back, brace harder and reduce the range of motion.
