Changes in Step Down Kinematics Following 16 Weeks of Supervised Progressive Resistance Training for People with Multiple Sclerosis

Background:  Progressive resistance training (PRT) has been reported to increase strength and gait velocity in persons with relapsing-remitting multiple sclerosis (RRMS) indicating an improvement to their functional ability. However, it is unclear if increased strength in persons with RRMS will result in similar changes to other functional tasks such as stepping off a curb or going down a step.

Objectives:  Determine the kinematic changes of a step down task for persons with RRMS who participate in 16 weeks of PRT.

Methods:  Nine individuals (8 females, 1 male) diagnosed with RRMS with an expanded disability status score of ≤6 participated in 16 weeks of PRT (age=44±12yr, height=1.7±0.1m, mass=77±23kg, EDSS=2.8±1.5). The PRT program followed the American College of Sports Medicine’s resistance training guidelines modified for persons with RRMS. The program included 3 supervised sessions per week on non-consecutive days. Resistance exercises were performed for all major muscle groups. Prior to and following 16 weeks of PRT, motion (100Hz) and ground reaction force signals (1000Hz) were collected while participants performed 5 step down trials at a self-selected speed. Step down height was set to 16cm to mimic the average height of a sidewalk curb. Research variables of interest included step down time and sagittal plane angular displacements for the lead and trail legs. Mean differences and standard error of the mean difference were calculated to provide a descriptive analysis of the pre- to post-intervention changes. Variables displaying a pre-to post-mean difference ≥0.1s for step down time and ≥3deg for angular displacements were considered clinically meaningful.

Results:  Following the PRT program, persons with RRMS displayed an 18% increase in leg strength (reported in a previous abstract) and a 10% decrease in step down time (mean difference = 0.162±0.070s). No other clinically meaningful kinematic changes were detected.

Conclusions:  Persons with RRMS were able to increase leg strength and perform the step down task more quickly, indicating a possible improvement in locomotor function following a 16-week PRT program. Furthermore, the ability to perform the step down task faster without losing balance may also indicate improved balance and possibly more confidence in their ability to step down from a raised surface. Although changes to sagittal plane angular displacements went undetected, persons with RRMS appear to benefit from participating in supervised PRT.