Shoulder pain and time dependent structure in wheelchair propulsion variability

Chandrasekaran Jayaraman, Yaejin Moon, Jacob J. Sosnoff

Research output: Contribution to journalArticlepeer-review


Manual wheelchair propulsion places considerable repetitive mechanical strain on the upper limbs leading to shoulder injury and pain. While recent research indicates that the amount of variability in wheelchair propulsion and shoulder pain may be related. There has been minimal inquiry into the fluctuation over time (i.e. time-dependent structure) in wheelchair propulsion variability. Consequently the purpose of this investigation was to examine if the time-dependent structure in the wheelchair propulsion parameters are related to shoulder pain. 27 experienced wheelchair users manually propelled their own wheelchair fitted with a SMARTWheel on a roller at 1.1m/s for 3min. Time-dependent structure of cycle-to-cycle fluctuations in contact angle and inter push time interval was quantified using sample entropy (SampEn) and compared between the groups with/without shoulder pain using non-parametric statistics. Overall findings were, (1) variability observed in contact angle fluctuations during manual wheelchair propulsion is structured (Z=3.15;p<0.05), (2) individuals with shoulder pain exhibited higher SampEn magnitude for contact angle during wheelchair propulsion than those without pain (χ2(1)=6.12;p<0.05); and (3) SampEn of contact angle correlated significantly with self-reported shoulder pain (rs (WUSPI) =0.41;rs (VAS)=0.56;p<0.05). It was concluded that the time-dependent structure in wheelchair propulsion may provide novel information for tracking and monitoring shoulder pain.

Original languageEnglish (US)
Pages (from-to)648-655
Number of pages8
JournalMedical Engineering and Physics
Issue number7
StatePublished - Jul 1 2016


  • Compensatory mechanisms
  • Complexity
  • Entropy
  • Human motor control
  • Manual wheelchair propulsion
  • Nonlinear analysis
  • Repetitive loading
  • Shoulder pain
  • Variation

ASJC Scopus subject areas

  • Biophysics
  • Biomedical Engineering


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