The Effects of Augmented Feedback With and Without Strength Training on Lower Extremity Biomechanics

Abstract

PURPOSE: To examine the effects of augmented feedback instruction with and without prior strength training on the lower extremity kinematics and kinetics of a stop-jump task. METHODS: A total of 58 recreational female athletes were randomly assigned to either an intervention (n=29, age=22.5±2.3 yrs, ht=1.67±.07 m, wt=64.1±9.1 kg) or control (n=29, age=22.5±3.8 yrs, ht=1.66±.06 m, wt=62.1±7.3 kg) group. Subjects completed either a 9-week lower extremity strength training program (intervention) or 9-weeks of no strength training (control). Lower extremity kinetics and kinematics were collected during 5 stop-jump trials at baseline and before and after both groups participated in an augmented feedback protocol subsequent to the 9 week period. The protocol consisted of subjects reviewing video of their own stop-jumps and those of an expert model. Feedback regarding standardized factors of optimal performance was provided. Dependent variables included peak knee anterior shear force (K-ASF); peak vertical ground reaction force, and knee flexion, hip flexion, knee valgus, and hip adduction joint angles at K-ASF. Statistical analyses were performed using a 2 [group] × 2 [time] repeated-measures ANOVA (α<.05). Dependent samples t-tests were performed to investigate significant interactions. RESULTS: No significant differences were observed between the control and intervention groups at baseline or prior to augmented feedback training. Significant main effects were observed for peak vertical ground reaction force (1.61 ±.64 BW vs 1.26±.41 BW, p<.001) and for knee flexion (27.2±7.0o vs 28.8±5.4o, p=.050), hip flexion (44.8±11.0o vs 51.8±8.9o, p<.001), and hip abduction (8.9±5.9o vs 11.3±8.7o, p=.032) angles subsequent to the augmented feedback protocol. Peak knee anterior shear force (.48±.18 BW vs .42±.14 BW, p=.015) and hip abduction angle (8.1±6.4o vs 12.8±6.1o, p<.001) were altered in the intervention group, but not the control group, subsequent to the augmented feedback protocol. CONCLUSIONS: The results indicate that strength training may have a positive amplifying effect on an augmented feedback technique intervention in female recreational athletes. This research may ultimately provide clinicians with a foundation on which to design effective and efficient ACL injury prevention programs.