Semi-Circle: Technique, Muscles Worked and Modifications

How to do the Semi-Circle

Lie on the Reformer with your toes lightly resting on the footbar, knees bent, and your shoulders resting on the headrest. Drop your pelvis down into the springs so your spine forms a comfortable arch.

1. Press your feet into the footbar to push the carriage out while keeping your pelvis low.
2. Once your legs are nearly straight, lift your hips up toward the ceiling to engage your gluteus maximus.
3. Keep your hips lifted high as you bend your knees to bring the carriage back in.
4. Slowly roll your spine down bone by bone until your pelvis drops back into the starting position.
5. After completing your repetitions in this direction, reverse the circle by lifting your hips first before pressing the carriage out.
6. Keep your hips lifted as your quadriceps push the carriage away.
7. Lower your pelvis down into the springs while your legs are extended.
8. Bend your knees to draw the carriage home with your pelvis remaining low.

• Breath. Teachers cue the breath differently, but you will often inhale as you press the carriage out and exhale to roll your spine down. Find a steady breathing rhythm that helps you maintain a slow, controlled pace.
• Where you feel it. You should feel your spinal extensors and gluteus maximus working hard, along with a stretch through the front of your chest and thighs. You should not feel sharp pinching in your lower back or excessive pressure on your neck.
• How many. 3 to 5 slow repetitions in each direction

Common mistakes

• Rushing the articulation. Take your time rolling through your spine bone by bone. Moving too quickly relies on momentum rather than your spinal extensors.
• Pushing with the neck. Keep the weight distributed across your upper back and shoulders on the headrest. Avoid pressing the back of your head aggressively into the headrest.
• Losing foot alignment. Keep your toes securely placed on the footbar with your heels lifted. Make sure your ankles stay stable as your legs push the carriage out.
• Dropping the hips early. Keep your gluteus maximus engaged to hold your hips high as you bend your knees to bring the carriage in. Wait until the carriage is home before rolling down.
• Forcing the extension. Only arch your back as far as feels comfortable for your spine. You want a smooth spinal extension, not a forced bend that strains your lower back.

Make it easier or harder

Easier

• Practice the basic bridging exercise on the mat to build gluteal strength and spinal articulation.
• Perform a standard bridge on the Reformer without dropping your pelvis into the springs.
• Limit the range of motion by making smaller circles with the carriage.

Who should be careful

• Back extension can irritate some conditions, such as spinal stenosis or spondylolisthesis. Keep the lift small or skip it if it brings on back or leg symptoms.
• Reformer springs and the moving carriage add load and instability. Learn it with a qualified instructor, who can set the springs for your body and goals.

Related exercises

• Jackknife Advanced
• Double Leg Kick Intermediate
• Quadruped Arm and Leg Reach Beginner
• Front Splits Advanced
• Swan Dive Advanced (prep version beginner)

When to see a doctor or physical therapist

• Sharp or shooting pain in your lower back during spinal extension.
• Numbness or tingling running down your legs.
• Pain or a pinching sensation in your neck while resting on the headrest.
• Sudden muscle spasms in your spinal extensors.

This page is general education, not a diagnosis or treatment plan. If you have a health condition, are pregnant or are recovering from an injury or surgery, check with your own clinician before trying new exercises.

How we put this page together. Exercise data (type, level, equipment and muscles) was compiled by our editors from the classical mat order in Joseph Pilates’ 1945 book and from commonly taught reformer repertoire. Muscle lists are a general anatomy guide; cueing differs between teachers. Text drafted with AI assistance and checked by the Editorial Team. See our editorial policy. Last checked October 2026.