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Large strengthening effect of a hip-flexor training programme: a randomized controlled trial



To investigate the effect on hip-flexion strength of a 6-week hip-flexor training programme using elastic bands as resistance. We hypothesized that the training group, compared to a control group, would increase their hip-flexion strength more.


Thirty-three healthy subjects (45 % females), 24(5) years of age, were included in a randomized controlled trial and allocated to heavy strength training of the hip-flexor muscles or to control (no strength training). Strength training of the hip-flexors (dominant leg) was performed three times 10 min per week for 6 weeks. The strength training group progressed from 15 repetition maximum (RM) (week 1) to 8 RM (week 6). Isometric hip-flexion strength (primary outcome) was measured by a blinded assessor using a reliable test procedure.


In the strength training group, the isometric hip-flexion strength of the trained leg increased by 17 %, (p < 0.001). The between-group difference in hip-flexion strength change in the trained leg (dominant leg, training group) versus the non-trained leg (dominant leg, control group) was significantly different from baseline to follow-up, corresponding to a mean change of 0.34 (95 % CI 0.17–0.52) Nm/kg, in favour of the strength training group (p < 0.001).


Simple hip-flexor strength training using elastic bands as external loading, for only 6 weeks, substantially improves hip-flexor muscle strength. This simple exercise programme seems promising for future prevention and treatment of acute and longstanding hip-flexor injuries, such as acute rectus femoris injuries and longstanding iliopsoas-related pain and impingement.

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External funding was received from Danish Regions for the current study. Thanks to Birk Mygind Grønfeldt, Stig Midtiby and Silje Marie Midtun for assisting with subject recruitment, training intervention and data collection. Also, thanks to the School of Physiotherapy, Metropolitan University College, Copenhagen, for providing training and testing facilities.

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There is no conflict of interest.

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Correspondence to Kristian Thorborg.

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Thorborg, K., Bandholm, T., Zebis, M. et al. Large strengthening effect of a hip-flexor training programme: a randomized controlled trial. Knee Surg Sports Traumatol Arthrosc 24, 2346–2352 (2016).

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  • Iliopsoas
  • Rectus femoris
  • Randomized controlled trial
  • Strengthening
  • Elastic bands