How is this different from a Side Plank?

Side Plank is a trunk exercise: both legs rest on the floor and the lateral core holds the body in line. Moving the top foot onto a bench and lifting the bottom leg shifts the job to the adductors of the top leg, which now have to support the hips. The trunk still works hard, but it is no longer the muscle group that fails first.

Should I start with the bent-knee version?

Yes, unless you already hold a long side plank comfortably and have trained your adductors directly. Copenhagen Plank (Bent Knee) rests the top knee and shin along the bench instead of the foot, which roughly halves the lever and makes the hold manageable while you learn to keep the hips stacked. Move the support out to the foot only once you can hold the bent-knee position for your full working time with the hips in line.

Does it actually help prevent groin injuries?

In semiprofessional male football players, a season-long program built on this exercise and its easier progression levels lowered the risk of reporting groin problems by 41% compared with training as usual. That trial was run in football, so the result does not automatically transfer to every sport, but it is the strongest evidence behind any single groin exercise.

How long should I hold it, and how often?

Two or three sets of 10 to 30 seconds per side is a sensible working range, trained two or three times a week with at least a day between sessions. Start at the low end of that range and add seconds before you add lever length.

Why is my inner thigh so sore the next day?

The adductors are loaded at a long length here and most people never train them directly, so a first exposure often leaves noticeable soreness for a day or two. Keep the first few sessions short, and the soreness usually settles within the first two or three weeks of consistent training.

How does it compare to Machine Hip Adduction?

Machine Hip Adduction works the same muscles seated with the back and pelvis supported and the resistance set on a stack, so the load is precise and easy to progress in small steps. The Copenhagen Plank offers only body weight and lever length as adjustments, but it loads the adductors at a long muscle length while the trunk and shoulder hold a side plank. Many trainers use both: the machine for controlled volume, this for the harder position.

Copenhagen Plank

What Is the Copenhagen Plank?

Copenhagen Plank is an isolation exercise that primarily targets the hips and groin, and also engages the obliques, glutes and shoulder stabilizers. It is an advanced-level movement held on the bottom forearm with the top foot resting on a flat bench and the bottom leg lifted clear of the floor, so the adductors of the top leg hold most of the body weight against gravity.

Almost all of the load sits on the top leg. The foot on the bench is the only point of support below the waist, and the adductors have to pull the thigh down toward the midline hard enough to keep the hips from sinking, while the bottom-side obliques stop the pelvis folding toward the floor. How far down the leg the support sits sets the difficulty: the closer to the foot, the longer the lever and the more force the groin has to produce. When hip adductor forces were modeled across eight common exercises in injury-free adults, the long-lever Copenhagen was the only one that ranked in the top tier for every adductor muscle measured, while the bent-knee version reached that tier for adductor brevis and adductor longus only.

The exercise came out of groin injury prevention work in soccer and has spread from there to hockey, field and court sports, and combat sports, wherever athletes cut, kick, skate or brace against a sideways load. It is usually programmed as accessory or warm-up work, two or three times a week with a day between sessions, and always on both sides. It is also listed as Side Plank Hip Adduction, which is a fair description of the setup, but the point of the movement is the adduction of the top leg rather than the trunk hold, and that is what separates it from Side Plank.

This long-lever version is not where most people should start. Build a clean 30-second Side Plank first so the shoulder and lateral trunk are not the limiting factor, then work through Copenhagen Plank (Bent Knee), which lays the top knee and shin along the bench and roughly halves the lever, before moving the support out to the foot. Machine Hip Adduction trains the same muscles seated with the trunk supported, so it is the better choice when you need a load you can set precisely or cannot yet hold the plank position.

The cue that matters most is where you feel the effort. It should burn along the inner thigh of the top leg, not in the supporting shoulder or the lower back. If the shoulder gives out first, the hips have dropped and the lever needs shortening.

Muscles Worked

MuscleActivation

Adductor Longus: Primary
Adductor Magnus: High
External Oblique: High
Deltoid: Medium
Gluteus Medius: Medium
Rectus Abdominis: Medium
Serratus Anterior: Medium
Erector Spinae: Low
Gluteus Maximus: Low
Rectus Abdominis (Lower): Low

Instructions

Set a flat bench beside you and lie on your side on the floor facing it, with your feet pointing toward the bench.
Place your bottom forearm on the floor with the elbow directly under your shoulder, bent to about 90 degrees, and rest your top hand on your chest or shoulder.
Lift the top leg and rest the inside of that foot on top of the bench, keeping the leg straight so the bench carries the foot alone and nothing above the ankle.
Let the bottom leg hang below the top one and allow your hips to settle toward the floor. This is the start position.
Press the top foot down into the bench and drive your hips up until your head, hips and top foot form one straight line.
Lift the bottom leg to meet the top leg so the ankles touch and the bottom foot stays clear of the floor.
Stack your hips and shoulders so the chest faces forward, not toward the floor, and keep your neck in line with your spine.
Hold the position for the prescribed time, breathing normally and keeping the inner thigh of the top leg working.
Lower the hips and the bottom leg under control back to the start position rather than dropping them.
Repeat on the other side for the same time.

Common Mistakes

Letting the hips sag
When the hips drop below the line from shoulder to top foot, the adductors stop holding the body up and the load shifts into the supporting shoulder and the lower back.
Setting the lever too long too soon
Supporting at the foot before the bent-knee version feels easy makes the position collapse within a few seconds.
Rolling the top hip backward
Letting the top hip and chest rotate toward the ceiling turns the hold into a half-supine position and takes tension off the adductors.
Resting the bottom foot on the floor
Touching the bottom foot down removes a large share of the load and quietly converts the set into an easier variation.
Misplacing the supporting elbow
An elbow set ahead of or behind the shoulder instead of directly under it pushes load into the shoulder joint and makes the hips harder to keep up.
Training one side harder than the other
Matching the weaker side's time on both sides matters here, because closing a side-to-side difference in adductor strength is much of the reason to do the exercise.

Injuries

Copenhagen Plank is a medium risk exercise when performed with proper technique. It uses no external load, but the long lever puts a large force through the adductors of the top leg while they are held at a long length, which is more than most people expect from a bodyweight hold.

The adductor longus and its attachment near the pubic bone take the brunt of it, and that is the tissue most often involved in groin strains. The supporting shoulder is the second strain point, because a sagging hip transfers load into the shoulder joint and the lower back at the same time. The top ankle and the inside of the lower shin can get sore where they press against the edge of the bench, which a folded towel under the contact point fixes. Pronounced inner-thigh soreness a day or two after the first few sessions is common and is not in itself a sign of injury.

Introduce the exercise with short holds of about 10 seconds per side and low volume, then add time before you add lever length. If the hips cannot stay in line for the whole hold, shorten the lever by sliding more of the leg onto the bench or drop back to Copenhagen Plank (Bent Knee). Side Plank is the right regression when the shoulder or the lateral trunk fails first, and Machine Hip Adduction lets you keep training the adductors at a load you choose while you build up to the plank position.

Stop the set if you feel a sharp or pinpoint pain at the groin or near the pubic bone, as opposed to a spreading burn in the muscle belly. This is a high-force exercise and it is not the one to load an acute adductor strain or an unexplained ongoing groin pain with, so get those assessed before using it, and reintroduce it through the bent-knee version rather than straight back at full lever length.

Overview

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

Alternative Exercises

Other Names for the Copenhagen Plank

The Copenhagen Plank is also known as:

Side Plank Hip Adduction
Copenhagen Adduction

Frequently Asked Questions

Q: How is this different from a Side Plank?: Side Plank is a trunk exercise: both legs rest on the floor and the lateral core holds the body in line. Moving the top foot onto a bench and lifting the bottom leg shifts the job to the adductors of the top leg, which now have to support the hips. The trunk still works hard, but it is no longer the muscle group that fails first.
Q: Should I start with the bent-knee version?: Yes, unless you already hold a long side plank comfortably and have trained your adductors directly. Copenhagen Plank (Bent Knee) rests the top knee and shin along the bench instead of the foot, which roughly halves the lever and makes the hold manageable while you learn to keep the hips stacked. Move the support out to the foot only once you can hold the bent-knee position for your full working time with the hips in line.
Q: Does it actually help prevent groin injuries?: In semiprofessional male football players, a season-long program built on this exercise and its easier progression levels lowered the risk of reporting groin problems by 41% compared with training as usual. That trial was run in football, so the result does not automatically transfer to every sport, but it is the strongest evidence behind any single groin exercise.
Q: How long should I hold it, and how often?: Two or three sets of 10 to 30 seconds per side is a sensible working range, trained two or three times a week with at least a day between sessions. Start at the low end of that range and add seconds before you add lever length.
Q: Why is my inner thigh so sore the next day?: The adductors are loaded at a long length here and most people never train them directly, so a first exposure often leaves noticeable soreness for a day or two. Keep the first few sessions short, and the soreness usually settles within the first two or three weeks of consistent training.
Q: How does it compare to Machine Hip Adduction?: Machine Hip Adduction works the same muscles seated with the back and pelvis supported and the resistance set on a stack, so the load is precise and easy to progress in small steps. The Copenhagen Plank offers only body weight and lever length as adjustments, but it loads the adductors at a long muscle length while the trunk and shoulder hold a side plank. Many trainers use both: the machine for controlled volume, this for the harder position.