The Copenhagen plank is a side plank with the top leg up on a bench. You lie on one forearm with the top foot on the support and lift your hips until your body is straight and the bottom leg comes up to meet the top one. You can hold that position, or lower and lift for reps.
Nobody is credited by name with inventing it; a web search on October 30, 2026 found no originator. E3 Rehab’s 2020 article notes that most research uses a partner-held version, the Copenhagen adduction exercise, named in a 2014 study from Copenhagen University Hospital. Brolic lists it as Copenhagen Plank, with no aliases, and logs it as a timed hold for each side: one logged set covers both sides, and the time entered is the hold on each side.
Muscles worked
Brolic tags the adductors, the inner-thigh muscles, as the primary muscle group, with the abdominals as secondary. E3 Rehab’s video names three adductors, the adductor magnus, brevis and longus, which bring the leg toward the midline, and says the Copenhagen plank challenges that action. Jessica Jennings, a physical therapist with 3DPT, describes using the top leg’s adductors to hold the position.
Two studies measured the Copenhagen adduction exercise. In the 2014 study of 40 elite male soccer players, adductor longus activity ranged from 14% to 108% of a maximal contraction across eight hip adduction exercises; the authors called the Copenhagen adduction dynamic and high-intensity, though the abstract does not give its own figure. In a 2016 trial with 24 under-19 players, those who added eight weeks of it to their training increased eccentric hip adduction strength by 35.7%; the control group did not change significantly.
Set up the support
Put something soft under your forearm and find a support for the top leg. E3 Rehab lists a chair, bench, barbell or Smith machine, padded if hard; a partner can hold the leg instead. Jennings uses a chair.
Choose the knee or the foot. With the top leg bent and the inside of the thigh near the knee on the support, the exercise is easier, E3 Rehab says. Jennings starts there, then moves the foot onto the chair, which lengthens the lever and makes it more challenging.
If the support is low, bend the bottom knee. E3 Rehab’s example is a couch or plyo box that stops you straightening the bottom leg.
Hold or lift
Lift the hips until the body is straight and the legs meet. E3 Rehab wants a straight line from head to feet seen from above as well as from the side. In the knee-on-chair version, Jennings drives the top knee down into the chair to lift the bottom leg.
For the hold, stay at the top for a set time. This is the version Brolic logs. E3 Rehab suggests 15 to 60 seconds depending on how hard it is for you, and says the holds should be hard. For her knee-on-chair hold, Jennings suggests trying to build up from 10 seconds to 20 and then 30.
For reps, lower slowly, tap the floor and lift again. E3 Rehab wants every rep slow and controlled, with no rest on the floor between reps. Jennings’s long-lever version keeps the top foot on the chair and brings the bottom leg up and down, with a small hip dip as the leg lifts as an option.
Easier or harder
| Side plank | Copenhagen plank, knee on support | Copenhagen plank, foot on support | |
|---|---|---|---|
| Top leg | On the floor | Bent, inner thigh near the knee on the support | Straight, foot on the support |
| Difficulty | — | Easier (E3 Rehab); Jennings’s starting point | Harder: a longer lever |
To make it harder still, E3 Rehab’s options are to raise the top leg further for more range or to hold a light weight on the hip. On the long lever, Jennings has you use the bottom leg for a little support from the floor at first and take it away as you get stronger.
For a general gym programme, E3 Rehab calls two to three sets of 6 to 15 reps, two to three times a week, reasonable. It also adds squats, split squats and step-ups, since the adductors help bend and straighten the hip; Brolic tags the adductors on the B-stance Romanian deadlift too.
Logging
Brolic logs Copenhagen Plank by duration, per side: one logged set covers both sides, and the time entered is the hold on each side. A 30-second set means 30 seconds on the left and 30 on the right.
In the set’s note, write whether the knee or the foot was on the support, and any weight on the hip. If you did the lift-and-lower version, write the reps per side there too. The weekly set tally shows how these sets add to your adductor work.
Common questions
Knee or foot first? Both sources treat the bent-knee version as the easier one, and Jennings’s progression starts there.
Does it prevent groin injuries? In a 2019 cluster-randomised trial, 35 semi-professional Norwegian men’s football teams (652 players) either added a programme built on the Copenhagen adduction or trained as normal; the weekly prevalence of groin problems over the season was 13.5% against 21.3%. The abstract does not say how the exercise was done. It is a study result, not advice about your groin.
It hurts. Stop the set.
Sources and method
- E3 Rehab: Copenhagen planks — anatomy, setup, reps and holds, easier and harder versions, programming; automatic captions. E3 Rehab’s 2020 article, by Tony Comella — research mostly uses the partner-held version.
- 3DPT, Jessica Jennings: Copenhagen plank progression — knee and foot positions, the knee drive, hold times, leg lifts, floor support; automatic captions and description.
- Serner et al. (2014), Ishøi et al. (2016) and Harøy et al. (2019) — adductor activity, eccentric strength and groin problems; abstracts only.
- Brolic catalog — name, per-side duration logging and muscle tags.
Hold times and rep ranges are the cited clinicians’ figures, not optima from a trial; the research is on the Copenhagen adduction exercise and is reported, not offered as advice.
