We studied the effect of aerobic training on conditioning in patients with limb-girdle muscular dystrophy type 2I (LGMD2I). Nine patients with LGMD2I cycled fifty 30-minute sessions at 65% of their maximal oxygen uptake over 12 weeks. Training significantly improved work capacity, paralleled by self-reported improvements. Creatine kinase levels did not increase significantly, and muscle morphology was unaffected. Moderate-intensity endurance training is a safe method to increase exercise performance and daily function in patients with LGMD2I.