Shoulder and Lower Back Joint Reaction Forces in Seated Double Poling

Area of Science:

• Sports biomechanics
• Exercise physiology
• Injury prevention

Background:

• Cross-country sit-skiing poses a risk for overuse injuries, particularly in the shoulders and lower back.
• Athletes with compromised trunk control often adopt a higher knee position (KH), increasing spinal flexion.
• A lower knee position (KL) using frontal trunk support may mitigate spinal flexion.

Purpose of the Study:

• To compare shoulder (glenohumeral) and L4-L5 joint reactions between KL and KH sitting positions during seated double poling.
• To investigate the biomechanical effects of different sitting positions on injury risk and performance in sit-skiing.

Main Methods:

• Utilized inverse-dynamics simulations based on measured pole forces and 3D kinematics from five female athletes.
• Analyzed musculoskeletal responses during submaximal and maximal exercise tests in both KL and KH positions on a ski ergometer.
• This study represents the first musculoskeletal simulation of seated double poling.

Main Results:

• The KH position demonstrated higher performance and reduced shoulder joint reactions in athletes with full trunk control.
• The KL position was associated with lower L4-L5 joint reactions, potentially decreasing lower back injury risk.
• Optimizing both performance and safety simultaneously in sit-skiing presents a significant challenge.

Conclusions:

• Different sitting positions in sit-skiing yield distinct biomechanical outcomes affecting performance and injury risk.
• The KH position may be preferable for performance and shoulder safety in athletes with adequate trunk control.
• The KL position offers potential benefits for reducing lower back strain and associated injury risks.