Increased muscle strength in paralyzed patients after spinal cord injury: Effect of beta-2 adrenergic agonist

The administration of β-2 adrenergic agonists in experimental animals result in an increased strength of skeletal muscle. In this study, we evaluated whether a β-2 adrenergic agonist, metaproterenol, had an effect on muscle size and strength in a group of patients with muscular atrophy following spinal cord injury. Ten male subjects were randomly divided into 2 groups and agreed to participate in a prospective, double-blind, placebo-controlled, and crossover study. Metaproterenol (80 mg/day), or placebo, was administered orally for a period of 4 weeks. Muscle strength was measured by a force transducer interfaced with a microcomputer. Muscle size was calculated and expressed as a cross-sectional area of upper arm and forearm using a formula. Metaproterenol induced a significant increase of muscle strength in both groups of subjects, compared with placebo (p < .001). Similarly, there was an increase in a muscle size in the forearm following the administration of metaproterenol. Our data indicate that β-2 adrenergic agonists may improve both muscle strength and size in patients with muscular atrophy following spinal cord paralysis.