Lower extremity muscle force measures and functional ambulation in patients with amyotrophic lateral sclerosis

Objective: To examine the relation between lower extremity muscle force production and functional ambulation in patients with amyotrophic lateral sclerosis (ALS). Design: Retrospective analysis of data collected from 1979 to 1995. Patients: Two hundred forty ALS patients referred to the New England Medical Center Neuromuscular Research Unit. Main Outcome Measures: Muscle force production during a maximum, voluntary isometric contraction of ankle dorsiflexors, knee flexors, knee extensors, hip flexors, and hip extensors was calculated as percent predicted maximal force (PPMF). Functional ambulation status was classified as unable, home, or community. Results: The probability of community ambulation compared with home increased with progressively higher PPMF for all muscle groups. Subjects with knee flexion strength greater than 75% PPMF were 395 times more likely to ambulate in the community. Subjects with hip extension strength over 50% PPMF showed improved chance of ambulation at home. Conclusion: Lower extremity PPMF is a critical factor determining functional ambulation in patients with ALS. Knee flexors play an important role in community ambulation while the hip extensors are important for home ambulation. (C) 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.