Shoulder pain and time dependent structure in wheelchair propulsion variability

Area of Science:

• Biomechanics
• Rehabilitation Engineering
• Musculoskeletal Health

Background:

• Manual wheelchair propulsion causes repetitive upper limb strain, often leading to shoulder pain.
• Existing research suggests a link between wheelchair propulsion variability and shoulder pain.
• The time-dependent structure of this variability remains under-explored.

Purpose of the Study:

• To investigate the relationship between the time-dependent structure of wheelchair propulsion parameters and shoulder pain.
• To determine if fluctuations in propulsion over time correlate with the presence and severity of shoulder pain.

Main Methods:

• 27 experienced manual wheelchair users propelled their wheelchairs on rollers at a constant speed (1.1 m/s) for 3 minutes.
• SMARTWheel technology was used to record propulsion data.
• Time-dependent structure of cycle-to-cycle fluctuations (contact angle, inter-push time) was quantified using sample entropy (SampEn).

Main Results:

• Variability in contact angle fluctuations during propulsion demonstrated a structured pattern (Z=3.15; p<0.05).
• Individuals experiencing shoulder pain showed significantly higher SampEn for contact angle compared to those without pain (χ(2)(1)=6.12; p<0.05).
• SampEn of contact angle significantly correlated with self-reported shoulder pain scores (rs (WUSPI) =0.41; rs (VAS)=0.56; p<0.05).

Conclusions:

• The time-dependent structure of wheelchair propulsion, specifically contact angle variability, is a significant factor in manual wheelchair users.
• Higher complexity in contact angle fluctuations is associated with shoulder pain in wheelchair users.
• Quantifying propulsion variability may offer novel insights for tracking and monitoring shoulder pain in this population.