This study examined the effects of exercise-induced muscle damage on tremor and proprioception components of neuromuscular function. Six male and six female volunteers (aged 18-30 yr) performed 50 maximal eccentric muscle actions using the forearm flexors of the nondominant arm. Forearm flexor tremor and perception of voluntary force and joint position were monitored to assess changes in neuromuscular function. Data were analyzed using REANOVA. Serum creatine kinase activity increased from a baseline value of 68 +/- 13 IU.l-1 to 2849 +/- 852 IU.l-1 5 d after exercise (P <0.05). This was accompanied by prolonged impaired joint range of motion (P <0.01) and reduced maximum strength (P <0.01). Muscle soreness peaked 3 d postexercise (P <0.01; Wilcoxon test). Tremor amplitude was increased (P <0.01) until 48 h after exercise, whereas the power frequency spectrum was unaffected. Perception of joint position at elbow angles of 1.57 rad (P <0.01) and 2.09 rad (P <0.05) and perception of force (P <0.01) were significantly impaired when the control arm acted as the reference. Joint positions were more accurately reproduced when the experimental arm acted as its own reference. The increase in tremor amplitude and loss of proprioceptive function in the days after damage-inducing eccentric exercise suggest significant impairment of neuromuscular function.