Abstract
In response to high rates of work-related musculoskeletal injury (MSI) in long-term care (LTC), decision makers have implemented minimal-lift policies to reduce strain arising from resident transferring, often advocating the use of lifting devices. Floor-based lifts, in particular, are widely used in LTC, even though users are known to experience potentially injurious forces when pushing overweight or obese residents on carpet (Marras, Knapik & Ferguson, 2009). Motivated by this, a European manufacturer has developed a motor-driven, floor-based lift to assist users with resident transferring (esense Rise, Active4Care, Enschede, NL). Despite the motor-driven lift’s promise as a strategy for improved workplace safety, no research has been published examining its ability to reduce external hand forces, or perceptions of ease among users, during pushing. Therefore, we compared external hand forces and subjective ratings of perceived ease when straight-line pushing a motor-driven versus conventional (manual wheeled) floor-based lift, under conditions of low (vinyl) and high (carpet) rolling resistance, and while transporting passengers of average (67 kg) and ninetieth percentile (90 kg) resident weight. We recruited fourteen female direct care staff from a partner LTC site in British Columbia, Canada. We collected external hand force data using a piezoelectric, triaxial load cell (model 9074C, Kistler, Winterthur, Switzerland), custom mounted between existing lift handholds and a cylindrical handlebar. We also collected information on exposure (frequency, distance) to pushing in LTC by questionnaire, and calculated participant-specific tolerance limits for initial and sustained forces using Snook and Ciriello’s (1991) Hazard Analysis Tool.
We observed a significant interaction between lift type and floor surface on initial (p < 0.001) and sustained (p < 0.001) forces. On vinyl, the motor-driven lift required, on average, 35 N (34%) less initial force (p < 0.001) and 14 N (27%) less sustained force (p < 0.001) than the conventional lift, regardless of resident weight. On carpet, we observed larger differences in forces between lifts, with the motor-driven lift requiring, on average, 64 N (36%) less initial force (p < 0.001) and 51 N (52%) less sustained force (p < 0.001) than the conventional lift, regardless of resident weight. Furthermore, there was an interaction between lift type and floor surface on subjective ratings of perceived ease of pushing (p < 0.001). On vinyl, subjective ratings did not differ between lifts (p = 0.32), with the majority of participants rating their ease of pushing as ‘very easy’ when pushing 90 kg passengers in both the conventional lift (n = 8, 57.1%) and the motor- driven lift (n = 12, 85.7%). On carpet, however, ratings were, on average, 1.8-points lower with the motor- driven lift (mean = 1.7; ‘somewhat easy’) than the conventional lift (mean = 3.5; ‘somewhat difficult’), independent of resident weight (p < 0.001). No conditions involving the motor-driven lift imposed forces above tolerable limits, while three of fourteen (21.4%) direct care staff exerted forces above tolerable limits when using the conventional lift on carpet only.
Our results did not demonstrate a clear need for a motor-driven lift to mitigate the biomechanical demands of linear pushing on vinyl, as no participants’ force values approached tolerable limits for either lift on vinyl. Subjective ratings were also no different between lifts on vinyl. We did, however, demonstrate that motor-driven lifts reduce the biomechanical demands associated with pushing floor-based lifts on carpet. This insight can be used to inform evidence-based practices to improve worker safety during resident transferring, which could lead to reductions in both the incidence and severity of work-related MSI in LTC.
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