Unrestricted Versus Restricted Anterior Knee Displacement During Bodyweight Squat Training in Physically Active Young Adults: An Exploratory Three-Arm Randomized Controlled Trial

Background/Objectives: Restricting anterior knee displacement is a common squat cue, but it redistributes rather than reduces mechanical demand, and comparative evidence is largely acute. This exploratory trial compared the short-term functional effects in healthy, active young adults. Methods: Sixty participants were randomized to unrestricted or restricted anterior knee displacement, or usual activity (three-arm, single-centre). Both exercise groups completed 18 remotely supervised bodyweight squat sessions over six weeks (720 repetitions; 100% session adherence among completers). The primary outcome was low-back-related disability (Oswestry Disability Index); 21 exploratory secondary outcomes covered pressure pain threshold, Y Balance Test reach, exertion, and jump flight time. Follow-up scores were compared by one-way analysis of variance, unadjusted for baseline, with post hoc ANCOVA sensitivity analyses as supplementary. Results: Fifty-seven of the 60 randomized participants completed the trial and were analysed (n = 19, 18, and 20). Follow-up Oswestry scores did not differ among groups, F(2,54) = 1.999, p = 0.145, η2 = 0.069; the largest pairwise difference was −2.9 percentage points (95% CI −5.9 to 0.0). Baseline disability was minimal (floor effect). In the unadjusted analysis, only the left-hamstring pressure pain threshold reached p < 0.05, not surviving multiplicity adjustment; baseline-adjusted sensitivity analyses left the primary result unchanged while strengthening several exercise-versus-control contrasts, two below the adjusted threshold—all exploratory. Comparable changes occurred in the untreated control group. Conclusions: Within the conditions of this short-term bodyweight-squat intervention, restricting anterior knee displacement provided no detectable advantage, and no clinically important between-group difference. The trial was not an equivalence study.