Sagittal-plane trunk position, landing forces, and quadriceps electromyographic activity

Area of Science:

• Biomechanics of sports injuries
• Injury prevention strategies
• Human movement analysis

Background:

• Anterior cruciate ligament (ACL) injuries are often linked to high landing forces, excessive quadriceps activity, and upright posture.
• While knee kinematics are well-studied, the role of trunk positioning in ACL injury risk factors remains under-explored.

Purpose of the Study:

• To investigate the impact of trunk flexion during the landing phase on ground reaction forces and quadriceps muscle activation.
• To assess whether trunk positioning can be a modifiable factor in reducing ACL injury risk.

Main Methods:

• A repeated-measures design involving 40 healthy volunteers (20 men, 20 women).
• Participants performed two drop-landing tasks: a natural landing and a landing with deliberate trunk flexion.
• Measurements included peak vertical and posterior ground reaction forces and mean quadriceps electromyographic amplitude during the loading phase.

Main Results:

• Trunk flexion significantly decreased both vertical ground reaction forces and quadriceps electromyographic amplitude (P < .001).
• No significant differences in the effects of trunk flexion were observed between sexes for landing forces or quadriceps activity.

Conclusions:

• Trunk flexion during landing effectively reduces biomechanical stress, including landing forces and quadriceps activation, thereby potentially mitigating ACL injury risk.
• This strategy also promotes greater knee and hip flexion, leading to a less erect landing posture.
• Emphasis on trunk flexion during landing should be considered a valuable component of ACL injury prevention programs.