Association of quadriceps and hamstrings cocontraction patterns with knee joint loading

Area of Science:

• Neuromuscular control
• Biomechanics
• Sports medicine

Background:

• Female athletes have a higher incidence of anterior cruciate ligament (ACL) injuries compared to male athletes.
• This disparity is linked to sex differences in lower extremity neuromuscular control, with women exhibiting greater knee valgus and abduction loads during landing.
• These loads increase ACL strain, potentially leading to injury.

Purpose of the Study:

• To investigate quadriceps and hamstrings muscle activation patterns in relation to peak knee abduction moments.
• To explore sex differences in neuromuscular control during a dynamic landing task.

Main Methods:

• Cross-sectional study involving 21 recreationally active adults (11 women, 10 men).
• Surface electromyography (EMG) of medial and lateral quadriceps and hamstrings, lower extremity kinematics, and kinetics were recorded during a 100-cm forward hop.
• Calculated quadriceps-to-hamstrings (QratioH) cocontraction indices, medial-to-lateral QratioH ratio, and normalized EMG data.

Main Results:

• Overall cocontraction was lower in women than in men.
• Muscle activation was lower in medial compared to lateral musculature in both sexes.
• The medial QratioH cocontraction index significantly explained variance in peak knee abduction moment in women.
• Women showed less activation in vastus medialis than vastus lateralis and in medial hamstrings than lateral hamstrings.

Conclusions:

• Medial-to-lateral QratioH cocontraction appears unbalanced in women, potentially impairing their ability to resist abduction loads.
• This imbalance may contribute to the higher ACL injury rates observed in female athletes.
• Restoring medial-to-lateral QratioH cocontraction balance could be a strategy to reduce ACL injury risk in women.