How long should I hold each side?

Start with 10 to 20 seconds a side for 3 sets and build to 30 seconds once the hip stays level for the whole hold. Past roughly 30 seconds the set turns into an endurance test, so it is better to make the exercise harder than to keep stretching the time.

What is the difference between this and the full Copenhagen Plank?

Only the contact point on the bench. Here the bent knee takes the weight, while the full version puts the ankle on the bench and moves the support much further from the hip, and a laboratory comparison in recreationally active adults found the long-lever version produced about 50% more peak eccentric hip adduction torque than the short-lever one. Move across to Copenhagen Plank once this version is easy.

Is this just a Side Plank with the leg on a bench?

No, the target is different. A side plank is a trunk exercise, while here the top leg presses into the bench and the groin holds the pelvis up, so the adductors are what fails first. Use Side Plank when the trunk is the weak link and this when the groin is.

Can I do it for reps instead of a hold?

Yes, and that is how the exercise is usually run in adductor strengthening programs. Lower the hip toward the floor and press it back up under control for 6 to 10 reps a side, keeping the same straight line at the top. Pick either the hold or the reps in a given session rather than doing both.

How often should I train it?

Two to three sessions a week while you are building the position, then once a week to keep it once the long-lever version is in the program. Leave a day between sessions at first, because adductor soreness in the first few weeks is common and training through it tends to end with people quitting the exercise.

Does it have to be a bench?

No, any stable surface at around knee height does the job, and a training partner can hold the leg instead. Avoid anything that can slide or tip, since the whole point is that the top leg can press down hard without the support moving.

Copenhagen Plank (Bent Knee)

What Is the Copenhagen Plank (Bent Knee)?

Copenhagen Plank (Bent Knee) is an isolation exercise that primarily targets the hips and groin and also engages the core and the supporting shoulder. It is an intermediate-level movement in which the body holds a side plank on one forearm while the top leg presses down into a bench, so the hip adductors have to hold the pelvis up against body weight. Keeping the top knee bent and resting it on the bench shortens the lever between the hip and the support, which is what makes this the version to start with.

The Copenhagen family of adduction exercises comes out of groin-injury prevention work in soccer, and that is still where it earns its place. Low hip adduction strength is a recognized risk factor for adductor-related groin problems, and the adductor longus is the muscle that has to decelerate the leg during kicking, reaching and hard changes of direction. A cluster-randomized trial in semi-professional male soccer players found that a season-long program built on a partner-assisted version of this exercise, worked through three progression levels, lowered the risk of reporting groin problems by 41%.

Almost all of the load sits on the top leg, where the adductor longus and adductor magnus do the holding. The obliques, the down-side glutes and the support shoulder work as stabilizers rather than as targets, so this is not a substitute for direct core or shoulder work. Moving the contact point from the knee out to the ankle is the main way the exercise is made harder; lifting the bottom leg clear of the floor instead of resting it there is the smaller step in between.

It suits soccer, hockey, handball and combat-sport athletes, clients returning to adductor loading once a groin problem has settled, and anyone who wants hip stability that a machine cannot train. If the side-plank position itself is the limit, build that first with Side Plank. If you want adductor load without holding your own body weight, Machine Hip Adduction gives it seated, through a smaller range and with no trunk demand at all. Once 30 seconds a side feels controlled here, the long-lever Copenhagen Plank is the next step.

Muscles Worked

MuscleActivation

Adductor Longus: Primary
Adductor Magnus: High
External Oblique: Medium
Gluteus Medius: Medium
Deltoid: Low
Erector Spinae: Low
Rectus Abdominis: Low
Sartorius: Low
Serratus Anterior: Minimal
Tensor Fasciae Latae: Minimal

Instructions

Set a flat bench beside you and lie on your side on the floor with your head away from the bench.
Prop yourself on your bottom forearm with the elbow directly under the shoulder and the hand resting in a loose fist.
Lay your top leg across the bench with the knee bent, so the knee and lower shin carry the weight rather than the foot alone.
Bend your bottom knee and let that leg hang just clear of the floor, and fold your top arm across your chest.
Stack your shoulders and hips so the chest stays square to the front and your head stays in line with your spine.
Press the top knee down into the bench and lift your hip until the shoulder, hip and top knee form a straight line.
Draw the bottom knee up until it meets the top leg and keep it there.
Hold the position for the target time, breathing steadily and keeping the hip from drifting backward.
Lower the hip to the floor under control, then set up and repeat on the other side.

Common Mistakes

Letting the hip sag
Allowing the hip to drift toward the floor during the hold takes the adductors off tension and hands the work to the lower back.
Rotating the chest toward the floor
Rolling the torso down turns the side plank into a front plank and lets the top leg push into the bench instead of pulling down on it.
Collapsing into the support shoulder
Hanging on the shoulder joint instead of pressing the forearm into the floor leaves the shoulder and neck sore long before the groin is trained.
Sliding out onto the foot
Creeping along until the foot rather than the knee carries the weight turns this into the long-lever version and steps the adductor load up sharply without you deciding to.
Folding at the hip
Letting the hips flex so the body bends at the waist shortens the adductors and quietly drops the load the exercise is meant to apply.

Injuries

Copenhagen Plank (Bent Knee) is a low risk exercise when performed with proper technique. It uses body weight only, and the bent knee keeps the load on the adductors well below what the long-lever version puts through them, which is exactly why it is the entry point into this family.

The adductor longus, near where it attaches to the pubic bone, is the tissue that complains first, and usually because the jump in load was too big rather than because the position was wrong. Adductor soreness in the day or two after the first few sessions is normal and settles as you adapt; groin pain that is sharp, that sits on one point, or that is still there at the next session is not, and it means dropping back. The supporting shoulder and the side of the neck are the other places people feel it, almost always from letting the shoulder sink toward the ear instead of pressing the forearm down into the floor, and letting the hip sag hands the work to the lower back.

Build the position before you build the load. If the side plank is already hard, spend a few weeks on Side Plank, and here let the bottom leg rest on the floor rather than holding it up. When 3 sets of 30 seconds a side feel controlled, move to the long-lever Copenhagen Plank instead of stretching the hold out. End the set as soon as the hip starts to drop or the chest rotates toward the floor, and stop the exercise entirely if you feel a sharp pull in the groin, which needs assessment before it is loaded again.

Overview

Primary Focus: Hips & groin
Equipment: Body weight and bench
Modality: Strength
Difficulty: Intermediate

Alternative Exercises

Other Names for the Copenhagen Plank (Bent Knee)

The Copenhagen Plank (Bent Knee) is also known as:

Side Plank Hip Adduction (Bent Knee)
Short Lever Copenhagen Plank

Frequently Asked Questions

Q: How long should I hold each side?: Start with 10 to 20 seconds a side for 3 sets and build to 30 seconds once the hip stays level for the whole hold. Past roughly 30 seconds the set turns into an endurance test, so it is better to make the exercise harder than to keep stretching the time.
Q: What is the difference between this and the full Copenhagen Plank?: Only the contact point on the bench. Here the bent knee takes the weight, while the full version puts the ankle on the bench and moves the support much further from the hip, and a laboratory comparison in recreationally active adults found the long-lever version produced about 50% more peak eccentric hip adduction torque than the short-lever one. Move across to Copenhagen Plank once this version is easy.
Q: Is this just a Side Plank with the leg on a bench?: No, the target is different. A side plank is a trunk exercise, while here the top leg presses into the bench and the groin holds the pelvis up, so the adductors are what fails first. Use Side Plank when the trunk is the weak link and this when the groin is.
Q: Can I do it for reps instead of a hold?: Yes, and that is how the exercise is usually run in adductor strengthening programs. Lower the hip toward the floor and press it back up under control for 6 to 10 reps a side, keeping the same straight line at the top. Pick either the hold or the reps in a given session rather than doing both.
Q: How often should I train it?: Two to three sessions a week while you are building the position, then once a week to keep it once the long-lever version is in the program. Leave a day between sessions at first, because adductor soreness in the first few weeks is common and training through it tends to end with people quitting the exercise.
Q: Does it have to be a bench?: No, any stable surface at around knee height does the job, and a training partner can hold the leg instead. Avoid anything that can slide or tip, since the whole point is that the top leg can press down hard without the support moving.