The purpose of this study was to determine the effect of eccentric muscle damage on recruitment threshold force and repetitive discharge properties of low-threshold motor units. Ten subjects performed four tasks involving isometric contraction of elbow flexors while electromyography (EMG) was recorded from human biceps brachii and brachialis muscles. Tasks were: 1) maximum voluntary contraction (MVC); 2) constant-force contraction at various sub-maximal targets; 3) motor unit recruitment threshold task; and 4) minimum motor unit discharge rate task. These tasks were performed on three separate days before, immediately after, and 24-hrs after eccentric exercise of elbow flexor muscles. MVC force declined (42%) immediately after exercise and remained depressed (29%) 24-hrs later, indicative of muscle damage. Mean motor unit recruitment threshold for biceps brachii was 8.4 ± 4.2 % MVC, (n=34) before eccentric exercise, and was reduced by 41% (5.0 ± 3.0 % MVC, n = 34) immediately after, and by 39% (5.2 ± 2.5 % MVC, n = 34) 24-hrs after exercise. No significant changes in motor unit recruitment threshold were observed in the brachialis muscle. However, for the minimum tonic discharge rate task, motor units in both muscles discharged 11% faster (10.8 ± 2.0 Hz vs 9.7 ± 1.7 Hz) immediately after (n=29) exercise compared with before (n=32). The minimum discharge rate variability was greater in brachialis muscle immediately after exercise (13.8 ± 3.1%) compared with before (11.9 ± 3.1%) and 24-hrs after exercise (11.7 ± 2.4%). No significant changes in minimum discharge rate variability were observed in the biceps brachii motor units after exercise. These results indicate that muscle damage from eccentric exercise alters motor unit recruitment thresholds for at least 24-hrs, but the effect is not the same in the different elbow flexor muscles.