Exploring the effects of a weighted vs unweighted low-dose isometric Copenhagen adduction exercise training programme on hip adduction and abduction strength: a randomised controlled trial in senior-level male amateur rugby union players

Key Points

1. This study looked at low dose weighted vs. unweighted Copenhagen isometric exercises. In the weighted group, significant between group differences were found in the hip adduction:abduction strength ratio.
2. The weighted Copenhagen adduction program did not increase hip/groin soreness compared to participants in the unweighted group.
3. Practitioners may want to consider not only using the weighted version of the Copenhagen exercise but also evaluate the dosage of exercise that is being prescribed to drive their desired adaptation.

BACKGROUND AND OBJECTIVE

The Copenhagen adduction exercise is a well-studied exercise which has been proven to increase eccentric and isometric adductor strength, hip abduction strength and hip add:abd strength ratios (1).

The objective of the study was to compare the effectiveness of a low-dose isometric weighted Copenhagen adduction exercise program and a low-dose unweighted Copenhagen adduction exercise program, specifically evaluating changes in hip adduction strength, hip abduction strength, and hip adduction:abduction strength ratio.

The Copenhagen adduction exercise has been proven to increase eccentric and isometric adductor strength, hip abduction strength and hip add:abd strength ratios.

Adding external load to an isometric Copenhagen adduction exercise provides an effective stimulus for hip strength gains compared to an unweighted low-dose isometric Copenhagen adduction program.

METHODS

31 male amateur rugby union players completed the study. Participants were excluded if they reported hip/groin pain at the beginning of the study but were included if they reported a previous hip/groin pain or injury.

The two-group parallel design lasted eight weeks (see exercises in video 1):

• Group 1 completed low-dose isometric weighted (20% of participant’s body mass) Copenhagen adduction exercise

• Group 2 completed low-dose isometric unweighted Copenhagen adduction exercise

VIDEO 1 – COPENHAGEN EXERCISES

Outcome measures:

1. Isometric hip adduction squeeze strength
2. Isometric hip abduction press strength
3. Hip adduction:abduction strength ratio
4. Hip/groin pain
5. Groin muscle soreness
6. Perceived loading measured after each exercise

RESULTS

The results from this study are summarized in table 1.

LIMITATIONS

Readers should acknowledge the following limitations of this study:

1. The study only included senior male rugby union players. Application to other sports, ages or sex is unknown.

2. The players continued with their regular sport training during the study. The impact of this activity is unknown.

CLINICAL IMPLICATIONS

This exploratory study compared the effects of a low-dose isometric weighted Copenhagen adduction exercise program and a low-dose isometric unweighted Copenhagen adduction exercise program on hip strength in senior-level male amateur rugby union players. The weighted group demonstrated significant within-group improvements in hip adduction strength (+10%), hip abduction strength (+4%), and hip adduction:abduction strength ratio (+7%). The unweighted group showed no significant changes. Between-group analysis further confirmed a favorable effect of weighted training on the adduction:abduction strength ratio.

These findings suggest that adding external load to an isometric Copenhagen adduction exercise provides an effective stimulus for hip strength gains compared to an unweighted low-dose isometric Copenhagen adduction program. This may contrast with prior studies (2) suggesting strength increases with unweighted training, though those study protocols included eccentric and concentric exercise variations, while this study focused solely on isometric loading.

Particularly relevant to the practitioner, the weighted Copenhagen adduction program did not increase hip/groin soreness which may lead to greater compliance and may give clinicians confidence in implementing this exercise during all parts of the season.

These results also highlight the potential of low-dose isometric weighted Copenhagen adduction exercise as a practical alternative for improving hip strength in senior rugby athletes, particularly during high-load training periods.

+STUDY REFERENCE

O' Connor C, Coyle E, Mc Intyre M, Delahunt E, Thorborg, K (2025) Exploring the effects of a weighted vs unweighted low-dose isometric Copenhagen adduction exercise training programme on hip adduction and abduction strength: a randomised controlled trial in senior-level male amateur rugby union players. Physical therapy in sport: official journal of the Association of Chartered Physiotherapists in Sports Medicine, 75, 29–37. Advance online publication.

SUPPORTING REFERENCE

1. Dawkins, J., Ishøi, L., Willott, J. O., Andersen, L. L., & Thorborg, K. (2021). Effects of a Low‐dose Copenhagen Adduction Exercise Intervention on Adduction Strength in Sub‐elite Male footballers: a Randomised Controlled Trial. Translational Sports Medicine, 4(4).
2. Ishøi, L., & Thorborg, K. (2021). Copenhagen adduction exercise can increase eccentric strength and mitigate the risk of groin problems: but how much is enough!. British journal of sports medicine, 55(19), 1066–1067.