Does disability level impact the relationship of muscle strength to walking performance in people with multiple sclerosis? a cross-sectional analysis

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.

Clinical utility of the Trendelenburg Test in people with multiple sclerosis

BACKGROUND

The clinical utility of the Trendelenburg Test remains unknown in people with multiple sclerosis (MS).

OBJECTIVE

To measure (1) intra-rater reliability, (2) agreement of goniometer-assessed Trendelenburg pelvis-on-femur angle (POF) with motion capture, and (3) concurrent validity of Trendelenburg POF and hip abduction strength with POF during walking and step negotiation.

METHODS

Trendelenburg POF was measured in 20 people with MS using goniometry and motion analysis. In addition, peak POF was measured using motion analysis during walking, step ascent, and step descent. Intra-rater reliability of goniometer-assessed Trendelenburg POF and agreement with motion analysis-assessed POF were analyzed. Pearson's r was used to determine the relationships between Trendelenburg POF and hip abduction strength with peak POF during each functional activity.

RESULTS

Goniometer-assessed Trendelenburg POF demonstrated very strong reliability (ICC: 0.948), strong agreement with 3D motion analysis (ICC: 0.792), correlated moderately with peak POF during walking (r = 0.519) and step ascent (r = 0.572), and weakly with step descent (r = 0.463). Hip abductor strength correlated weakly with peak POF during step ascent (r = -0.307) and negligibly during walking (r = -0.270) and step descent (r = -0.249).

CONCLUSIONS

Goniometer-assessed Trendelenburg POF was reliable, agreed with motion analysis, and may provide insight into hip abduction muscle performance during functional activities in people with MS.

Functional Performance, Leg Muscle Strength, and Core Muscle Endurance in Multiple Sclerosis Patients With Mild Disability: A Cross-Sectional Study

This study aimed to investigate the relationship of sit-to-stand and walking performance with leg muscle strength and core muscle endurance in people with multiple sclerosis (PwMS) with mild disabilities. In this study, 49 PwMS (Expanded Disability Status Scale score = 1.59 ± 0.79) and 26 healthy controls were enrolled. The functional performances, including sit-to-stand and walking performances, were evaluated with the five-repetition sit-to-stand test, timed up and go test, and 6-min walking test. The PwMS finished significantly slower five-repetition sit-to-stand, timed up and go, and 6-min walking test than the healthy controls. In addition, the significant contributors were the weakest trunk lateral flexor endurance for five-repetition sit-to-stand; the Expanded Disability Status Scale score, and the weakest hip adductor muscle for timed up and go; the weakest hip extensor muscles strength for 6-min walking test. The functional performances in PwMS, even with mild disabilities, were lower compared with healthy controls. Decreases in both leg muscle strength and core muscle endurance are associated with lower functional performance in PwMS.