This study's aims were (1) to test whether training on an arm ergometer improves motor performance, and (2) to develop a technique to quantify individual muscle spasticity. Nine patients with a stabilized hemisyndrome (in average 22 months after ischemic stroke in the territory of middle cerebral artery) underwent a 3-week training on an arm ergometer, 5 days/week. The patients were tested one week before training, at training onset, at the end of training and 2 weeks after training. Spasticity was quantified by (1) the Ashworth Scale of the elbow flexors and extensors, (2) the maximum active extension of the biceps, and (3) the minimum torque on the lesioned side during arm cycling. The data were standardized, pooled and a 2-way ANOVA revealed a decrease of the spasticity by the training (p=0.076). Similarly muscle force was evaluated by the Rivermead Motorik Assessment, the Motricity Index and the cycling force, and the range of active movement as the sum of the angles at a maximum shoulder flexion, shoulder abduction, elbow flexion and elbow extension. The training increased the force (p<0.01) and also the range of motion (p<0.05) significantly. The patients confirmed the clinical relevance of the results. The spasticity index - the relation between the muscle activity modulation on the normal and lesioned side - was shown to be a useful tool in quantifying individual muscle spasticity. It was concluded that cycling on an arm ergometer is a useful tool for rehabilitation.