Establishment of regression-based normative isometric strength values for major lower limb muscle groups in persons with multiple sclerosis.

BACKGROUND: Limb weakness is a major impairment that affects mobility in persons with multiple sclerosis (PwMS). Specifically, lower limb (LL) weakness can greatly affect gait and balance, while increasing fall risk and decreasing quality of life. Numerous studies have compared LL strength of PwMS to healthy controls, however none have objectively measured strength in all major LL joints (hip, knee, and ankle) in a large number of PwMS. Additionally, while discrete normative values exist for knee extensors in PwMS, there has yet to be regression-based normative isometric strength values for all major LL muscle groups. Therefore, this study aimed to develop gender-specific regression-based normative prediction equations, with 95% confidence intervals, for maximal isometric peak torque of major LL muscles in PwMS. A secondary aim was to characterize the prevalence of LL weakness in PwMS, defined as ≥ 2 SD below values reported for healthy individuals. METHODS: A convenience sample of 175 (women: n = 135) PwMS participated in a prospective, cross-sectional study where isometric peak torque of hip flexors, extensors, and abductors, knee flexors and extensors, and ankle plantarflexors and dorsiflexors were measured using the Biodex System 4 Pro-Dynamometer®. Demographics (age, height, and weight) and disease characteristics (disease duration and disability) were collected. Performances were separated for each muscle group into strongest limb and weakest limb. For each gender, regression-based equations were generated for the LL muscle groups by limb with age, height, weight, disability, and disease duration as the covariates. Descriptive statistics were used to examine the frequency of LL weakness by gender and disability level. For comparison purposes, age-stratified (<30, 30-39, 40-49, 50-59, 60-69, >70 years) and disability-stratified (mild, moderate, and severe ambulant) discrete peak torque values were also generated for each gender. RESULTS: Regression-based normative data are presented for men and women, accounting for age, height, weight, disability, and disease duration. Men were significantly stronger (P < 0.001) than women for all LL, with the men's models accounting for a greater percent of muscle strength variation than women's models for all muscle groups, except for hip extension. Disability was inversely related to strength in all of the models. LL weakness was prevalent in hip flexion (m: 47.5%; w: 63.0%) and extension (m: 92.5%; w: 88.1%), knee extension (m: 30.0%; w: 33.3%) and flexion (m: 25.0%; w: 34.8%), and ankle plantarflexion (m: 15.0%; w: 10.4%) and dorsiflexion (m: 100.0%; w: 96.3%). PwMS with mild disability had a high prevalence of ankle dorsiflexion (94.9-100.0%) and hip extension (81.4-90.0%) weakness. CONCLUSIONS: This study is the first to provide regression-based normative data of bilateral strength in all major LL muscle groups and clinically useful prevalence data on the occurrence of weakness in these muscles. Of note, PwMS had a high prevalence of ankle dorsiflexion and hip extension weakness even when they were only mildly disabled. These findings can help guide the direction of future interventions and treatments to improve muscle function in PwMS.

The Role of Cognitive Impairment on Physical Therapy Attendance and Outcomes in Multiple Sclerosis.

BACKGROUND AND PURPOSE: Many persons with multiple sclerosis (PwMS) experience cognitive impairments, which may affect their ability to engage in physical therapy. There is limited information on how cognitive impairments are associated with PwMS' ability to participate and improve their functional outcomes. This study aimed to assess the relationship between cognitive functioning and PwMS' attendance, total goal attainment, and functional improvement following physical therapy intervention. METHODS: Participants (n = 45) were PwMS who participated in a larger self-management study and enrolled in physical therapy within the past 2 years. Objective cognitive functioning was examined using tests of prospective memory, retrospective memory, working memory, and processing speed, along with a self-report measure. Bivariate analyses were conducted to examine the relationship between cognitive functioning and each physical therapy outcome (session attendance, attaining goals, and changes in functional outcome measures), followed by logistic regressions with age, education, gender, and disability level as covariates. RESULTS: Difficulty learning new verbal information was associated with a greater likelihood of "no showing" one or more of their physical therapy sessions. Reductions in working memory and processing speed were associated with PwMS not meeting all their rehabilitation goals. Despite deficits in new learning, memory, and processing speed, 85.2% of those with pre-/postscores showed improvements in at least one functional outcome measure following physical therapy intervention. DISCUSSION AND CONCLUSIONS: These findings demonstrate the ability for PwMS to make functional motor gains despite the presence of cognitive impairments and highlight the potential contributions of cognitive functioning on attendance and goal attainment of physical therapy intervention.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A362, which includes background, methods, results, and discussion in the authors' own voices).