Improved Quadriceps Torque Production With Optimized Biofeedback in Patients After Anterior Cruciate Ligament Reconstruction

Abstract

Hogg, JA, Barger, NB, Bruce, JR, White, CC, Myer, GD, and Diekfuss, JA. Improved quadriceps torque production with optimized biofeedback in patients after anterior cruciate ligament reconstruction. J Strength Cond Res XX(X): 000–000, 2024—Optimizing performance through intrinsic motivation and attention for learning: prevention rehabilitation exercise play (OPTIMAL PREP) training strategies incorporate motor learning principles to enhance movement acquisition and retention. We aimed to use OPTIMAL PREP biofeedback to evaluate its potential to improve quadriceps and hamstring torque production in patients with anterior cruciate ligament reconstruction (ACL-R). Thirteen subjects 23 ± 19 months post ACL-R completed 5 concentric quadriceps/hamstrings repetitions on an isokinetic dynamometer for each limb and counterbalanced condition at 60°·s−1. For the control condition, subjects were instructed to perform the exercise “as hard and fast as possible.” For the OPTIMAL PREP condition, subjects were additionally told that “Research shows that if you focus on moving the line on the screen (external focus) you will exhibit greater quadriceps output (enhanced expectancies)” and were given the choice of graphical representation for the biofeedback (autonomy support). Quadriceps and hamstrings peak torque, rate of force development, and torque-angle waveforms were analyzed with 2 × 2 RMANOVAs (a priori >0.06). The ACL-R limb demonstrated increased quadriceps peak torque in the OPTIMAL PREP condition than in the control condition ( = 0.13, interaction p = 0.21, pairwise Cohen's d = 0.63). Anterior cruciate ligament reconstruction limb quadriceps deficits remained near terminal extension (14–45°; peak Cohen's d = 0.57, p < 0.001). For hamstrings peak torque, we observed moderate effects for condition (OPTIMAL PREP greater; = 0.10, p = 0.29) and limb (uninvolved greater; = 0.13, p = 0.22). Easily implementable OPTIMAL PREP training strategies improved ACL-R limb quadriceps torque production, resulting in between-limb parity. However, asymmetries still existed near terminal extension.