Feedback Leads to Better Exercise Quality in Adolescents with Patellofemoral Pain

PURPOSE: Adolescents with patellofemoral pain (PFP) do not comply with their exercise prescription, performing too few and too fast repetitions, compromising recovery. We investigated if real-time feedback on contraction time would improve the ability of adolescents with PFP to perform exercises as prescribed.

METHODS: A randomised, controlled, participant-blinded, superiority trial with a 6-week intervention of three weekly sessions of three elastic band exercises was undertaken. Forty 15 to 19-year-old adolescents with PFP were randomised to real-time BandCizer™-iPad feedback on contraction time or not by a physiotherapist. The primary outcome was the mean deviation from the prescribed contraction time of 8 seconds per repetition. Secondary outcomes included isometric hip and knee strength, Kujala Patellofemoral Scale and Global Rating of Change.

RESULTS: The mean deviation from prescribed 8 seconds per repetition contraction time was 1.5s (±0.5) for the feedback group, compared to 4.3s (±1.0) for the control group (mean difference: 2.7s (95% CI: 2.2-3.2, P<0.001). Based on total contraction time during the intervention, the feedback group received 35.4% of the prescribed exercise dose whilst the control group received 20.3%. Isometric hip and knee strength increased significantly more in the feedback group compared to controls (mean difference = 1.35 N/kg (95%CI: 0.02-2.68, P=0.047)). There were no significant differences in Kujala Patellofemoral Scale and Global Rating of Change between groups, but the study was not powered for this.

CONCLUSION: Real-time feedback on contraction time resulted in the ability to perform exercises closer to the prescribed dose, and also induced larger strength gains.