INTRODUCTION: In this study we investigated the effect of 12 weeks of cycle ergometer training in patients with spinal muscular atrophy type III (SMA III), a hereditary motor neuron disease with progressive muscle weakness and atrophy.

METHODS: Six SMA III patients and 9 healthy subjects completed a 12-week training program, performing 42 30-minute sessions exercising at 65-70% of maximal oxygen uptake (VO2max ). VO2max , muscle strength, functional tests, and self-reported activities of daily living were assessed before and after the training.

RESULTS: Training induced a 27 ± 3% increase in VO2max (17 ± 2 to 21 ± 2 ml/kg/min, P < 0.001) in patients. However, fatigue was a major complaint and caused 1 patient to drop out, increased the need for sleep in 3 patients, and led to training modifications in 2 patients.

CONCLUSIONS: Cycle exercise improves VO2max in SMA III without causing muscle damage, but it also induces significant fatigue. This warrants study into alternative training methods to improve exercise capacity in SMA III patients.