Scapula kinematics differ by body mass index

Area of Science:

• Biomechanics
• Orthopedics
• Human Movement Science

Background:

• Increased arm mass in individuals with high body mass index (BMI) may alter shoulder biomechanics.
• Scapula kinematic alterations are linked to shoulder pain and pathology, potentially impacting overweight and obese individuals.
• Understanding BMI's effect on scapular motion is crucial for shoulder health assessment.

Purpose of the Study:

• To investigate differences in scapula biomechanics between higher and lower BMI groups during arm elevation.
• To determine if BMI influences scapulothoracic kinematics, particularly upward rotation.
• To explore potential biomechanical adaptations in individuals with higher BMI.

Main Methods:

• Collected 3D scapula kinematic data during arm elevation in 41 subjects.
• Compared kinematic data between a higher BMI group (BMI ≥ 27) and a lower BMI group (BMI ≤ 23).
• Utilized mixed-model ANOVA to analyze differences with and without holding a 1.36 kg weight.

Main Results:

• The higher BMI group demonstrated significantly greater scapula upward rotation at 120° compared to the lower BMI group.
• This difference was observed in both unweighted and weighted arm elevation tasks.
• Altered scapulothoracic movement was evident in individuals with higher BMI.

Conclusions:

• Higher BMI is associated with altered scapulothoracic movement, specifically increased upward scapular rotation.
• This kinematic change may represent an adaptive strategy to manage increased arm mass.
• Findings suggest a potential link between high BMI, altered scapular kinematics, and rotator cuff pathology.