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This study compared resistance-trained and untrained men for changes in commonly used indirect markers of muscle damage after maximal voluntary eccentric exercise of the elbow flexors. Fifteen trained men (28.2 [+ or -] 1.9 years, 175.0 [+ or -] 1.6 cm, and 77.6 [+ or -] 1.9 kg) who had resistance trained for at least 3 sessions per week incorporating exercises involving the elbow flexor musculature for an average of 7.7 [+ or -] 1.4 years, and 15 untrained men (30.0 [+ or -] 1.5 years, 169.8 [+ or -] 7.4 cm, and 79.9 [+ or -] 4.4 kg) who had not performed any resistance training for at least 1 year, were recruited for this study. All subjects performed 10 sets of 6 maximal voluntary eccentric actions of the elbow flexors of one arm against the lever arm of an isokinetic dynamometer moving at a constant velocity of 90[degrees]*[s.sup.-1]. Changes in maximal voluntary isometric and isokinetic torque, range of motion, upper arm circumference, plasma creatine kinase activity, and muscle soreness before, immediately after, and for 5 days after exercise were compared between groups. The trained group showed significantly (P < 0.05) smaller changes in all of the measures except for muscle soreness and faster recovery of muscle function compared with the untrained group. For example, muscle strength of the trained group recovered to the baseline by 3 days after exercise, where the untrained group showed approximately 40% lower strength than baseline. These results suggest that resistance-trained men are less susceptible to muscle damage induced by maximal eccentric exercise than untrained subjects. KEY WORDS muscle damage, muscle soreness, isometric strenght, isokinetic strenght, range of motion, plasma creatine kinase activity