Isometric tests to evaluate upper and lower extremity functioning in people with multiple sclerosis: reliability and...

Area of Science:

• Neurology
• Rehabilitation Medicine
• Biomedical Engineering

Background:

• Motor symptoms in upper and lower extremities are prevalent in people with multiple sclerosis (PwMS).
• Objective, reliable, and valid outcome measures are needed to assess neuromuscular functioning in PwMS.
• This study evaluated standard and novel isometric tests for PwMS.

Purpose of the Study:

• To assess the reliability and external validity of novel isometric tests for upper (grip force) and lower extremity (knee extensors) neuromuscular functioning in PwMS.
• To determine the relationship between isometric measures and functional performance tests.
• To identify predictors of functional outcomes in PwMS.

Main Methods:

• Twenty-nine relapsing-remitting PwMS underwent two visits for isometric and functional testing.
• Isometric tests included maximum voluntary contraction, rate of force development, and a novel brief force pulse (BFP) protocol measuring force development and relaxation scaling factors (RFD-SF, RFR-SF).
• Functional tests included grip force, finger tapping, 25-ft walk test, timed up and go, 5-times sit-to-stand, and the Multiple Sclerosis Spasticity Scale.

Main Results:

• Most isometric measures demonstrated high reliability (ICCs > 0.87).
• In upper extremities, RFD-SF and RFR-SF correlated with functional tests (9-hole peg, finger tapping).
• In lower extremities, RFR-SF showed the strongest correlations with functional tests (walking speed, TUG, sit-to-stand, spasticity scale) and EDSS score.

Conclusions:

• The BFP protocol offers reliable and relevant outcome measures for assessing upper and lower extremity function in PwMS.
• Muscle relaxation rate (RFR-SF) is a key predictor of walking speed in PwMS.
• These findings support the use of BFP for evaluating neuromuscular deficits and functional capacity in multiple sclerosis.