Association of quadriceps and hamstrings cocontraction patterns with knee joint loading

Abstract

Context: Sex differences in neuromuscular control of the lower extremity have been identified as a potential cause for the greater incidence of anterior cruciate ligament (ACL) injuries in female athletes compared with male athletes. Women tend to land in greater knee valgus with higher abduction loads than men. Because knee abduction loads increase ACL strain, the inability to minimize these loads may lead to ACL failure.

Objective: To investigate the activation patterns of the quadriceps and hamstrings muscles with respect to the peak knee abduction moment.

Design: Cross-sectional study.

Setting: Neuromuscular research laboratory.

Patients or other participants: Twenty-one recreationally active adults (11 women, 10 men).

Main outcome measure(s): Volunteers performed 3 trials of a 100-cm forward hop. During the hop task, we recorded surface electromyographic data from the medial and lateral hamstrings and quadriceps and recorded lower extremity kinematics and kinetics. Lateral and medial quadriceps-to-hamstrings (QratioH) cocontraction indices, the ratio of medial-to-lateral QratioH cocontraction, normalized root mean square electromyographic data for medial and lateral quadriceps and hamstrings, and peak knee abduction moment were calculated and used in data analyses.

Results: Overall cocontraction was lower in women than in men, whereas activation was lower in the medial than in the lateral musculature in both sexes (P < .05). The medial QratioH cocontraction index (R(2) = 0.792) accounted for a significant portion of the variance in the peak knee abduction moment in women (P = .001). Women demonstrated less activation in the vastus medialis than in the vastus lateralis (P = .49) and less activation in the medial hamstrings than in the lateral hamstrings (P = .01).

Conclusions: Medial-to-lateral QratioH cocontraction appears to be unbalanced in women, which may limit their ability to resist abduction loads. Because higher abduction loads increase strain on the ACL, restoring medial-to-lateral QratioH cocontraction balance in women may help reduce ACL injury risk.

Keywords: anterior cruciate ligament; biomechanics; coactivation; landings; neuromuscular system.

Figures

Figure 1. Retroreflective marker placement. A, Front view. B, Side view. The markers on the medial aspect of the knee, on the medial aspect of the ankle, and on the left and right anterior-superior iliac spine were used only during a static trial (to configure each participant with the global coordinate system) and were removed before the dynamic landing trials were performed.

Figure 2. Mean (± SD) lateral and medial Q∶H cocontraction indices for women and men participants. Both men and women demonstrated lower medial Q∶H cocontraction than lateral Q∶H cocontraction.

Figure 3. Medial Q∶H cocontraction plotted against the external knee abduction moment in female participants.

Figure 4. Ratio of medial-to-lateral Q∶H cocontraction for the women and men participants. The ratio of cocontraction was lower for women than for men (P < .05).

Figure 5. Mean (± SD) normalized peak knee abduction moments for women and men participants. Abduction moments were higher for women than for men (P < .05).

Figure 6. Mean (± SD) normalized lateral quadriceps EMG for women and men participants. Women displayed greater vastus lateralis activation than vastus medialis activation (P  =  .49).

Figure 7. Mean (± SD) normalized lateral and medial hamstrings EMG for women and men participants. Women displayed greater lateral hamstrings activation than medial hamstrings activation (P  =  .01).