Lower extremity muscle strength across the adult lifespan in multiple sclerosis: Implications for walking and stair climbing capacity

Abstract Introduction Persons with multiple sclerosis (pwMS) accumulate impairments in muscle strength and limitations in physical function as the disease progresses. The same symptoms are seen in the biological process of aging (years of age > 60 years). Nonetheless, no previous studies have examined the combined effects of aging and multiple sclerosis (MS) in regards to lower extremity muscle strength concomitant with physical function (e.g. walking capacity). The aim of this cross-sectional study was to examine potential differences in pwMS vs. healthy controls (HC) across the adult lifespan in these outcomes. Methods A total of n = 53 pwMS and n = 48 age-matched HC were enrolled, and divided into groups of young (≤ 44 years), middle-aged (45–59 years), and old (≥ 60 years). Assessment of knee extensor (KE) and plantar flexor (PF) muscle force-velocity characteristics (isometric and dynamic concentric force at contraction velocities of 0–300 degs−1) alongside assessment of timed 25 ft walk tests (T25FWT), two minute walk tests (2MWT), and 9-step stair ascend (9SSA) were carried out. Results Overall, substantial impairments in KE and PF isometric (ranging from −18 to −23%) and dynamic muscle strength (ranging from −26 to −38%) alongside limitations in T25FWT, 2MWT, and 9SSA (ranging from −24 to −33%) were observed in pwMS vs. HC (p  Conclusion Substantial impairments of KE and PF muscle strength occur in pwMS across the adult lifespan accompanied by/associated with limitations in walking and stair climbing capacity, with PF muscle strength being preferentially affected in pwMS vs. HC.