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Feedback Leads to Better Exercise Quality in Adolescents with Patellofemoral Pain


Medicine & Science in Sports & Exercise: January 2018 - Volume 50 - Issue 1 - p 28–35
doi: 10.1249/MSS.0000000000001412
Clinical Sciences

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 randomized, controlled, participant-blinded, superiority trial with a 6-wk intervention of three weekly sessions of three elastic band exercises was undertaken. Forty 15- to 19-yr-old adolescents with PFP were randomized 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 s 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 s per repetition contraction time was 1.5 ± 0.5 s for the feedback group, compared with 4.3 ± 1.0 s for the control group (mean difference: 2.7 s (95% confidence interval = 2.2–3.2, P < 0.001). On the basis of total contraction time during the intervention, the feedback group received 35.4% of the prescribed exercise dose whereas the control group received 20.3%. Isometric hip and knee strength increased significantly more in the feedback group compared with controls (mean difference = 1.35 N·kg−1, 95% confidence interval = 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.

1Department of Health Science and Technology, Faculty of Medicine, Center for Sensory–Motor Interaction (SMI), Aalborg University, Aalborg, DENMARK; 2Research Unit for General Practice in Aalborg, Department of Clinical Medicine, Aalborg University, DENMARK; 3School of Health and Rehabilitation Sciences, The University of Queensland, St. Lucia, Queensland, AUSTRALIA; 4Physical Medicine and Rehabilitation Research–Copenhagen (PMR-C), Department of Physical Therapy and Department of Orthopedic Surgery, Clinical Research Centre, Copenhagen University Hospital, Amager-Hvidovre, Copenhagen, DENMARK; 5Sports Orthopedic Research Center–Copenhagen (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Copenhagen, DENMARK; and 6Department of Occupational Therapy and Physiotherapy, Aalborg University Hospital, Aalborg, DENMARK

Address for correspondence: Henrik Riel, M.Sc., Research Unit for General Practice in Aalborg, Aalborg University, Fyrkildevej 7, 9220 Aalborg, Denmark; E-mail:

Submitted for publication July 2017.

Accepted for publication August 2017.

© 2018 American College of Sports Medicine