Trunk position influences joint activation pattern and physical performance during vertical jumping.

Area of Science:

• Biomechanics
• Human Movement Science
• Sports Physiology

Background:

• Joint recruitment patterns and their influence on jumping performance are critical in athletic movements.
• Understanding the role of trunk position in optimizing force production during jumps is essential for training.
• Previous research has explored jump mechanics, but the specific interplay between trunk angle, range of motion, and joint activation requires further elucidation.

Purpose of the Study:

• To investigate the effect of trunk position on joint recruitment patterns during squat jumps (SJS, SJL) and countermovement jumps (CMJS, CMJL).
• To determine how varying ranges of motion (small vs. large) and trunk posture influence jumping height.
• To analyze the contribution of different joints (ankle, knee, hip) to vertical propulsion under distinct jump conditions.

Main Methods:

• Eight well-trained male athletes performed squat jumps and countermovement jumps with both large and small ranges of motion.
• A key criterion for small range of motion jumps (SJS, CMJS) was maintaining a near-vertical trunk position.
• Film analysis was used to measure joint angles, activation times, maximum joint velocities, vertical propulsion time, and jumping height.

Main Results:

• Joint activation followed a proximal-to-distal pattern in most conditions (CMJL, SJL, CMJS), but reversed in the SJS (small range of motion, vertical trunk).
• The ratio of active state to vertical propulsion time was significantly lower for hip and knee joints in SJS compared to other conditions.
• Jumping height differences were significantly greater between CMJS and SJS (small range of motion) than between CMJL and SJL (large range of motion).

Conclusions:

• A small range of motion combined with a vertical trunk position limits the ability of knee and hip muscles to contribute effectively during the push-off phase.
• This limitation in muscle contribution directly results in reduced jumping height when the trunk is vertical and range of motion is restricted.
• Optimal jump performance may necessitate a larger range of motion and/or a non-vertical trunk posture to maximize positive work from key lower limb joints.