Exercise programs have been shown to increase strength and endurance in patients with myopathic disorders. The authors investigated the effect of aerobic training in patients with facioscapulohumeral dystrophy (FSHD). Twelve weeks of low-intense aerobic exercise improved maximal oxygen uptake and workload with no signs of muscle damage. The authors conclude that aerobic training is a safe method to increase exercise performance in patients with FSHD.

Muscle glycogen storage diseases are rare inborn diseases caused by errors of metabolism associated with either dynamic, exercise-related symptoms or permanent muscle weakness. The most common glycogen storage disease, McArdle's disease (glycogen storage disease type V), is caused by myophosphorylase deficiency and characterized by cramps and muscle pain elicited by sudden vigorous exercise, which may lead to rhabdomyolysis and myoglobinuria. Diagnosis can be suggested by the absence or blunting of the increase in lactate level and the exaggeration of the ammonia response in venous effluent blood in the forearm of a person who is exercising. One exception is that lactate and ammonia responses may be normal in patients with phosphorylase b kinase deficiency (glycogen storage diseases type VIII).¹

Objective: To assess whether bezafibrate increases fatty acid oxidation (FAO) and lowers heart rate (HR) during exercise in patients with carnitine palmitoyltransferase (CPT) II and very long-chain acyl-CoA dehydrogenase (VLCAD) deficiencies. Methods: This was a 3-month, randomized, double-blind, crossover study of bezafibrate in patients with CPT II (n = 5) and VLCAD (n = 5) deficiencies. Primary outcome measures were changes in FAO, measured with stable-isotope methodology and indirect calorimetry, and changes in HR during exercise. Results: Bezafibrate lowered low-density lipoprotein, triglyceride, and free fatty acid concentrations; however, there were no changes in palmitate oxidation, FAO, or HR during exercise. Conclusion: Bezafibrate does not improve clinical symptoms or FAO during exercise in patients with CPT II and VLCAD deficiencies. These findings indicate that previous in vitro studies suggesting a therapeutic potential for fibrates in disorders of FAO do not translate into clinically meaningful effects in vivo. Classification of evidence: This study provides Class I evidence that bezafibrate 200 mg 3 times daily is ineffective in improving changes in FAO and HR during exercise in adults with CPT II and VLCAD deficiencies.

Patients with the myopathic form of carnitine palmitoyltransferase II (CPT II) deficiency typically experience muscle pain, cramps, and myoglobinuria during prolonged exercise. It has been suggested that carriers of CPT2 gene mutations also may have milder clinical symptoms, but fatty acid oxidation (FAO) has never been investigated in vivo in this group. We studied fuel utilization by indirect calorimetry and stable isotope methodology in four patients with CPT II deficiency, three subjects who carried one CPT2 gene mutation, and five healthy control subjects. Cycle exercise at a constant workload of 50% of maximal oxygen uptake capacity was used to facilitate FAO. We found that in vivo oxidation of long‐chain fatty acids was normal at rest but severely impaired during prolonged, low‐intensity exercise in patients with CPT II deficiency, and that two of the single CPT2 gene mutation carriers, who displayed symptoms of CPT II deficiency, had an FAO comparable with the patients. These results indicate that residual CPT II activity is sufficient to maintain long‐chain FAO at rest in CPT II deficiency but not to increase FAO during exercise. The findings also suggest that single CPT2 gene mutations may exert a dominant‐negative effect on the tetrameric CPT II protein. Ann Neurol 2005;57:60–66

It is generally believed that a diet high in carbohydrate improves exercise tolerance in patients with carnitine palmitoyltransferase II (CPT II) deficiency, but it has never been systematically investigated. The authors investigated the effect of a high- vs low-carbohydrate diet on exercise tolerance in four patients with CPT II, who cycled at a constant workload of 50% of Vo_2max. Exercise tolerance, assessed by exercise duration and perceived exertion, improved on the carbohydrate-rich diet.