J. Sternhagen, F. Akram, & B. Bowser, PhD.
South Dakota State University, Brookings, SD

Research in Multiple Sclerosis (MS) suggests lower extremity asymmetry can negatively influence gait and balance which may lead to increased risk of falls. It is likely that leg strength asymmetry contributes to these negative effects. Currently there is limited research examining leg strength asymmetries in persons with MS. Purpose: To quantify lower extremity strength asymmetry during isometric and isokinetic knee extensor (KE) movements for people with MS. Methods: Leg strength was assessed bilaterally in 6 participants with MS (Expanded Disability Status Scale = 4.25± 2.36, Multiple Sclerosis Impact Scale-29 = 69.83±36). A Biodex dynamometer was used to bilaterally measure peak isometric KE torque at 90° and peak isokinetic KE torque at 30°/s, 60°/s, 90°/s, and 180°/s. Testing used a double baseline in which 3 trials were taken at each speed and position on two separate visits within a one-week period. Knee extensor strength for each limb was defined by the highest KE torque value from both sessions and for each exercise. These values were scaled to body mass. The mean and SD for each position and speed were recorded. Percent difference between limbs for each exercise was used to describe limb differences. Results: KE torque for isometric tests was 14% lower in the more affected leg (1.79±0.9 BW) compared to the less affected leg (2.06±0.7BW). Similarly, for isokinetic speeds of 30°/s and 60°/s, the more affected limb strength was respectively 23% and 25% lower than the less affected limb (30°/s: 1.39±0.6 vs. 1.75±0.3 BW; 60°/s: 1.16±0.5 vs. 1.48±0.5 BW ). For isokinetic speeds of 90°/s and 180°/s, the more affected limb strength was respectively 24% and 23% lower than the less affected limb (90°/s: 0.99±0.5 vs. 1.25±0.5 BW; 180°/s: 0.78±0.4 vs. 0.98±0.4 BW). Conclusions: These data provide evidence of leg strength asymmetries associated with MS. Possible effects include increased gait asymmetry and variability, and increased risk of falls.

NACSM Professional Sponsor: Bradley Bowser

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