Proposing a new index to quantify instantaneous symmetry during manual wheelchair propulsion

Abstract

Propelling a manual wheelchair (MWC) is a strenuous task that causes upper limb musculoskeletal disorders (MSD) in a large proportion of MWC users. Although most studies on MWC propulsion biomechanics assume that MWC propulsion is a relatively symmetric task, recent literature suggests that this is the case only when the assessed outcome measures are averaged over long periods of time, and not over short periods (i.e., instantaneously). No method is currently available to assess instantaneous symmetry. In this work, we present the Instantaneous Symmetry Index (ISI), a new method that quantifies how a variable has been instantaneously asymmetric during a selected time period. Thirteen experienced MWC users propelled on different cross slopes of 0%, 2%, 4%, 6% and 8%. As the cross slope is increased, the upper hand produced less propulsive moments and the lower hand produced more propulsive movements. This has been reflected in the ISI, which increased from 0.20 (0% slope) to 0.84 (8% slope) with a Spearman׳s coefficient of 0.90. The ISI has great potential to evaluate the ability of a user to propel symmetrically and synchronously, and will be a relevant measure to include in future studies on the impact of MWC propulsion asymmetry on MSD risk.

Sprint performance and propulsion asymmetries on an ergometer in trained high‐ and low‐point wheelchair rugby players

“…Interestingly, the assumption of whether wheelchair propulsion is considered a symmetric bimanual task has recently resurfaced during conditions of daily manual wheelchair propulsion while propelling at a low‐intensity steady‐state velocity . Although for a balanced wheelchair‐user combination the PO on average must be the same on both sides (ie, symmetric) to propel in a straight line, how this power production comes about can differ between the left and right sides and is almost never the same when comparing the left and right push cycle directly to each other (ie, asymmetric).…”

Relationship of Force–Velocity Profile between Field Sprints and Lab Ballistic or Cycling Ergometer for Wheelchair Basketball Players

“…The Instantaneous Symmetry Index (ISI) was calculated for the three tests, according to the method proposed by Chenier et al ( 2017) [31]. The ISI was defined as the absolute area between the right and the left side curves of the assessed variable, normalized by the sum of the absolute areas under both curves (Figure 2).…”

Trunk and glenohumeral joint adaptations to manual wheelchair propulsion over a cross-slope: An exploratory study

“…8 On the other hand, the uphill wheel was reported to have a negative mechanical power as it regulates the wheelchair trajectory. 9 As the amplitude of handrim forces, the rate of loading and shoulder kinematics are correlated with musculoskeletal injury, [10][11][12] the increased asymmetry and biomechanical load 9,13 observed for cross-slope propulsion might increase musculoskeletal injury. Thus, this skill requires specific training of the MWUs to insure a safe and efficient technique.…”