How many springs should I use?

Start with two springs and work down to one. The heavier setting keeps the carriage closer and helps draw the legs back together, so the movement stays controllable while it is new, and lightening it later leaves more of the closing work to the inner thighs.

How far should the carriage travel?

Only as far as you can keep the pelvis level and both legs straight, and never farther than you can pull back without the carriage crashing into the stopper. For most people that is well short of a full side split, and the range widens on its own as strength and hip range improve.

Does this train the inner or the outer thigh?

Both, and the spring decides the balance between them. The inner thighs control the legs opening and do the work of closing them, the outer hip holds the pelvis level throughout, and a lighter spring shifts more of that closing work onto the inner thighs.

What if my balance is shaky on the moving carriage?

Keep a hand on a pole or on the reformer frame and use a small range until standing feels steady, or build the same inner-thigh strength off the machine first with Machine Hip Adduction. Standing on a sliding surface is a skill of its own, and it improves quickly with short, low-range sets.

Where does the Side Split belong in a session?

Late, once the hips are warm and the lying and kneeling reformer work is done. Three to five slow reps per side with a pause at the open position is usually enough, since it is a control exercise rather than one to chase volume on.

Pilates Reformer Side Split

What Is the Pilates Reformer Side Split?

Pilates Reformer Side Split is an isolation exercise that primarily targets the hips and groin, and also engages the glutes, quadriceps and core. It is an intermediate-level movement performed standing on the reformer, with one foot on the moving carriage and the other on the stationary platform at the footbar end, so the legs open and close in the frontal plane against spring tension while the torso stays tall.

The springs run from the carriage to the footbar end of the frame, so the further the carriage travels the harder it is pulled back toward the standing foot. Opening the legs means letting the carriage slide out under control, and closing them means drawing the inner thighs together to bring it home. That gives the adductors a long, continuous range of loaded work that floor-based standing exercises rarely offer, and it trains them both to check a widening stance and to reverse it.

In the reformer repertoire the Side Split belongs to the standing work placed near the end of a session, once the hips are warm and the lying and kneeling exercises are done. Trainers use it as an inner-thigh and balance piece rather than a heavy strength lift, so a handful of slow reps per side with a pause at the open position does more than chasing repetitions. The frontal-plane pattern also carries over to sports that push off sideways, such as skating, tennis and field sports, where the groin has to check a wide stance and pull it back.

Spring load is the main variable. More spring tension shortens the travel and helps the legs close, which keeps the movement manageable, while a lighter spring leaves more of the closing work to the inner thighs. Arm position sets the balance demand: holding the arms straight out to the sides is the standard version, and resting a hand on a pole or on the frame makes it steadier. The Side Split suits anyone with reliable balance and comfortable inner-thigh range, and if either is missing it is worth building strength first with Machine Hip Adduction and getting used to the carriage with lying work such as Pilates Reformer Lying Pelvic Lift.

Muscles Worked

MuscleActivation

Adductor Longus: Primary
Adductor Magnus: Primary
Gluteus Medius: High
Gluteus Minimus: Medium
Vastus Lateralis: Medium
Vastus Medialis: Medium
External Oblique: Low
Gluteus Maximus: Low
Tensor Fasciae Latae: Low
Peroneus Longus: Minimal

Instructions

Load one or two springs and lower the footbar flat so the top of the carriage is clear.
Stand beside the reformer facing out over its long side, and place one foot flat on the carriage just in front of the shoulder rests.
Step the other foot onto the standing platform at the footbar end so both feet are in line along the machine.
Set the feet parallel with the outside edge of each foot near the edge of its platform, and keep the arches lifted rather than letting the feet roll inward.
Stand tall with both legs straight and the pelvis level, and reach the arms straight out to the sides at shoulder height.
Let the carriage slide away from the footbar, opening the legs only as far as you can keep the pelvis level and both legs straight.
Pause with the legs open and the weight shared evenly between the two feet.
Draw the inner thighs together to bring the carriage back to the stopper, slowing it so it arrives quietly.
Repeat for reps, then step off, turn to face the other way and work the other leg on the carriage.

Common Mistakes

Opening too far
Letting the legs travel past the range you can reverse, which turns a controlled strength exercise into an uncontrolled stretch on loaded adductors.
Crashing the carriage
Giving in to the springs on the way back so the carriage slams into the stopper instead of arriving under inner-thigh control.
Dropping one hip
Letting the pelvis tilt or sink toward the carriage side as the legs open, which shifts the work off the inner thighs and makes the range look bigger than it is.
Standing on the platform leg
Loading the stationary foot and letting the carriage leg ride along, so only one side does any real work.
Jamming the knees back
Pushing the knees into hyperextension for a feeling of stability, which loads the joint instead of the muscles around the hip.
Rolling onto the inner edge of the feet
Allowing the arches to collapse as the legs widen, which lets the knees drift inward and takes the inner thighs out of a strong position.

Injuries

Pilates Reformer Side Split is a medium risk exercise when performed with proper technique. Two things raise the stakes above a floor-based inner-thigh exercise: the adductors are loaded at long length at the open end of the range, which is the position groin strains tend to happen in, and the surface under one foot moves, so a loss of control costs balance rather than just a rep.

The groin and inner thigh take most of the strain, usually at the moment the carriage is out and the legs have to reverse direction. The inside of the knee can also complain if the knees are jammed back into hyperextension to feel stable. Warm the hips up before reaching for this one, keep the knees straight but not locked, and treat the return as the working half of the rep. If you cannot draw the carriage back without it crashing into the stopper, you opened too far.

Keep the spring load high enough that the travel stays inside a range you own, and shorten the range rather than the spring when you get tired. Hold a pole or the reformer frame with one hand until you can stand steadily without it, and step off before fatigue makes the standing leg wobble. Build the underlying strength with Machine Hip Adduction and, for inner-thigh work off the machine, Copenhagen Plank (Bent Knee). Progress by lightening the spring, then by widening the range and holding the open position for a few counts.

Stop the set for a sharp or pulling sensation high on the inner thigh, pain at the pubic bone, or pain on the inside of the knee. Anyone with a recent adductor strain, a painful hip or an unreliable sense of balance should leave standing work on a moving carriage for later, and anyone with pelvic girdle pain in pregnancy should clear it with a clinician before trying it.

Overview

Primary Focus: Hips & groin
Equipment: Pilates reformer
Modality: Strength
Difficulty: Intermediate

Alternative Exercises

Frequently Asked Questions

Q: How many springs should I use?: Start with two springs and work down to one. The heavier setting keeps the carriage closer and helps draw the legs back together, so the movement stays controllable while it is new, and lightening it later leaves more of the closing work to the inner thighs.
Q: How far should the carriage travel?: Only as far as you can keep the pelvis level and both legs straight, and never farther than you can pull back without the carriage crashing into the stopper. For most people that is well short of a full side split, and the range widens on its own as strength and hip range improve.
Q: Does this train the inner or the outer thigh?: Both, and the spring decides the balance between them. The inner thighs control the legs opening and do the work of closing them, the outer hip holds the pelvis level throughout, and a lighter spring shifts more of that closing work onto the inner thighs.
Q: What if my balance is shaky on the moving carriage?: Keep a hand on a pole or on the reformer frame and use a small range until standing feels steady, or build the same inner-thigh strength off the machine first with Machine Hip Adduction. Standing on a sliding surface is a skill of its own, and it improves quickly with short, low-range sets.
Q: Where does the Side Split belong in a session?: Late, once the hips are warm and the lying and kneeling reformer work is done. Three to five slow reps per side with a pause at the open position is usually enough, since it is a control exercise rather than one to chase volume on.