Power production during the five times sit to stand test in people with multiple sclerosis

Background: Multiple sclerosis (MS) is a neurological condition that impairs motor and sensory function, leading to challenges with movement, balance, and an increased risk of falls. Many falls occur during transfer movements, making assessments like the five times sit-to-stand test (5XSST) valuable for evaluating transfer ability and lower-body strength. Understanding the kinetic differences and relationships in transfer performance in people with MS (PwMS) can inform strategies to reduce fall risk. Methods: 5XSST data was collected on a force plate from 29 PwMS and 27 age- and sex-matched neurotypical (NT) controls. Vertical ground reaction forces (vGRF) were recorded to quantify peak force, rate of force development (RFD), and mean lower-body power during the 5XSST. Additionally, estimated power was calculated using equations incorporating anthropometric variables and task completion time. Results: PwMS displayed slower 5XSST completion times (p=0.011), reduced peak vGRF (p=0.011), a slower RFD (p<0.001), and lower mean power (p=0.003) compared to NT controls. Estimated power, moderately correlated with instrumented power measures (r=0.53, p=0.003), with stronger correlations when the estimation equation incorporated leg length (r=0.59, p<0.001). Among PwMS, those who reported a prior fall demonstrated reduced instrumented power (p=0.026) and estimated power (p=0.028) compared to non-fallers. Conclusion: PwMS exhibit distinct weight transfer strategies during the 5XSST, with reduced lower-body power serving as a possible marker of heightened fall risk. These findings highlight the need for rehabilitation strategies that improve lower-body power and for clinical measures that quickly and accurately assess power deficits and fall risk in PwMS.