Short- and long-term effects of endurance training in patients with mitochondrial myopathy.

Background and purpose:  It is unknown whether prolonged training is a safe treatment to alleviate exercise intolerance in patients with mitochondrial DNA (mtDNA) mutations. Methods:  The effect of 3 and 12 months training and 3–12 months deconditioning was studied in four patients carrying different mtDNA mutations. Results:  Three-month moderate-intensity training increased oxidative capacity by 23%, which was sustained after 6–12 months of low-intensity training. Training and deconditioning did not induce adverse effects on clinical symptoms, muscle morphology and mtDNA mutation load in muscle. Conclusion:  Long-term training effectively improves exercise capacity in patients with mitochondrial myopathy, and appears to be safe.