BACKGROUND Short-term strict immobilization of the arm using a cast enhances recovery of muscle function after eccentric exercise. OBJECTIVE To determine if placing one arm in a sling ("light" immobilization) for 4 days after eccentric exercise of the elbow flexor muscles would reduce muscle soreness and enhance recovery compared with the exercised but not immobilized contralateral arm. METHODS Subjects performed 10 sets of 6 maximal isokinetic (90 degrees x s(-1)) eccentric actions of the elbow flexors of each arm on a Cybex dynamometer, separated by 2 weeks. METHODS University laboratory. METHODS Ten healthy subjects (5 men and 5 women) with no history of upper arm injury or resistance training. METHODS One randomly assigned arm was placed in a sling for 4 days after the 30-minute postexercise measurement to secure the elbow joint at 90 degrees ; the contralateral arm received no treatment. The subject removed the sling when showering and sleeping and during postexercise measurements. METHODS We used an activity monitor to record upper arm activity before and after immobilization. We also compared changes in maximal isometric and isokinetic voluntary strength, range of motion, upper arm circumference, plasma creatine kinase activity, and muscle soreness during 7 days postexercise between arms with a 2-way, repeated-measures analysis of variance. RESULTS Eccentric exercise resulted in large losses in both isometric and isokinetic maximal voluntary contraction forces (approximately 40%), reduced range of motion (approximately 20%), increased arm circumference (approximately 10 mm), elevated plasma creatine kinase activity (approximately 2000 IU x L(-1)), and development of delayed-onset muscle soreness. No significant differences were noted between conditions for any measure except upper arm circumference, which increased significantly less for the immobilization than the control arm at 7 days postexercise (P < .05). CONCLUSIONS Light immobilization had no effect on enhancing recovery of muscle function and delayed-onset muscle soreness after eccentric-exercise-induced muscle damage.