The Effect of an 8‐Week Low‐ or High‐Volume Protocol of the Adductor Strengthening Programme on Hip Adduction Strength in Female Football Players—A Randomized Trial

The aim of this study was to investigate if an 8-week high-volume protocol of the Adductor Strengthening Programme was more effective than a low-volume protocol in increasing and maintaining isometric hip adduction strength in female football players. We randomized 52 players from the Norwegian women's 1st and 2nd division to a low-volume (220 reps/side) or high-volume (394 reps/side) group. Both groups performed an 8-week protocol of the Adductor Strengthening Programme and a 10-week maintenance protocol with 1 session/week (16 reps/side/session). We measured isometric hip adductor torque (Nm/kg) in a long-lever squeeze test (at 0° and 15° hip abduction) using the ForceFrame at baseline, weeks 4, 6, 8, and 18. Both groups increased their isometric hip adduction strength over the 8-week period (low-volume 0°: 0.13 [95% CI: 0.07-0.20] Nm/kg, 15°: 0.22 [95% CI: 0.07-0.36] Nm/kg; high-volume 0°: 0.13 [95% CI: 0.04-0.22] Nm/kg, 15°: 0.31 [95% CI: 0.18-0.45] Nm/kg), with no between-group difference in either test position (0°: -0.01 [95% CI: -0.11-0.01] Nm/kg; 15°: 0.10 [95% CI: -0.09-0.29] Nm/kg). Also, both groups maintained their strength throughout the 10-week maintenance period, with no between-groups difference in either test position (0°: 0.12 [95% CI: -0.01-0.24] Nm/kg; 15°: 0.06 [95% CI: -0.11-0.23] Nm/kg). Our results indicate that an 8-week high-volume protocol of the Adductor Strengthening Programme was not more effective in increasing isometric adductor strength in female football players than a low-volume protocol. Both groups increased their strength over the 8-week training period and maintained their strength during the 10-week maintenance period. Trial registration: The study protocol was uploaded to Open Science Framework before unblinding and analyzing the data (https://osf.io/7xfw4/).