To investigate the effects of real-time feedback regarding the anteroposterior center-of-pressure (AP-COP) position on asymmetrical biomechanics during double-leg squatting after ACLR.
Twenty-six individuals who had undergone unilateral ACLR participated (9 female participants, age 18.9 ± 3.6 years, since time surgery 4.5 ± 2.1 months). The participants performed double-leg squats under two conditions (baseline and COP feedback conditions). In the baseline condition, no specific instructions regarding the squatting technique were provided. In the COP feedback condition, the participants received real-time visual feedback regarding the AP-COP position for each foot and were asked to maintain a symmetrical AP-COP position as much as possible. Kinetic analysis was performed using a three-dimensional motion analysis system combined with two force plates. The limb symmetry index (involved limb/uninvolved limb×100[%]) was calculated for the knee extension moment, and participants with a knee extension moment LSI of less than 90% were included in the statistical analysis. Two-way repeated measures analysis of variance (condition × limb) and post-hoc Bonferroni test were used for comparisons of the AP-COP position and knee extension moment.
Thirteen participants (one female participant, age 19.9 ± 4.1 years, 4.1 ± 1.3 months since surgery) showed the asymmetry in knee extension moment (90%). At baseline, the mean COP position for the involved limb was significantly more anterior than that for the uninvolved limb (mean difference: 6.2 ± 8.1%; 95%CI: 1.5–11.0% foot length; P = 0.015). For the feedback condition, the between-limb difference in the mean AP-COP position decreased compared to the baseline, but the difference was still significant (mean difference 2.3 ± 2.4%, 95%CI: 0.8–3.7% foot length, P = 0.006). A significant condition-by-limb interaction effect was found for mean knee extension moment (P = 0.024). At the baseline, the knee extension moment for the involved limb was significantly smaller than that for the uninvolved limb (involved limb: 0.57 ± 0.12 Nm/kg, uninvolved limb: 0.75 ± 0.14 Nm/kg, P 0.001), and the limb symmetry index was 76 ± 12%. For the feedback condition, the limb symmetry index of the mean knee extension moment increased to 88 ± 18%, while a significant between-limb difference was detected (involved limb: 0.58 ± 0.13 Nm/kg, uninvolved limb: 0.68 ± 0.17 Nm/kg, P = 0.004).
The present study included individuals who showed obvious asymmetry in the knee extension moment during double-leg squatting. Although the asymmetry was not completely resolved, feedback training to maintain a symmetrical COP position improved symmetry in the knee extension moment during the double-leg squat exercise after ACLR. However, asymmetry was mainly addressed in the uninvolved limb, and this point needs to be improved in future studies.
Real-time feedback on AP-COP position would improve symmetry in biomechanics during double-leg squatting after ACLR.
Exercise
Neuromuscular control
