Physical training in myopathy: yes or no? This highlights a long-standing dilemma, and one that is still a matter of debate and controversy. Is it beneficial, at least to avoid muscle deconditioning, or detrimental, even harmful, because of the mechanical stress imposed to wrecked myofibres? An initial consideration is that little attention has been given to the different responses to training that the various myopathic conditions can produce. A second, consequential one, is that lack of unequivocal results and flaws in the training protocols let physicians take a somewhat empirical attitude—dictated by personal inclinations, common sense, indulgence toward patient compliance or just prudence inspired by ‘ primum non nocere - first do not harm’, an old evergreen precept (Hippocrates, 460–377 BC). In many cases, the final persuasion is that physical exercise is not recommended, through anxiety over the risk of damaging an already compromised muscle, or even triggering acute episodes of pain, rhabdomyolysis and myoglobinuria. The latter are certainly contraindications to strenuous physical exercise, for instance in several metabolic myopathies related to impaired energy metabolism, such as the lipid storage myopathies, due to defects of intra-mitochondrial transport and utilization of fatty acids (Bruno and DiMauro, 2008; e.g. carnitine-palmitoyl transferase II deficiency, electron transfer flavoprotein dehydrogenase (ETF-DH) deficiency, and very long-chain fatty acid β-oxidation defects) or glycogen (DiMauro, 2007; e.g. myophosphorylase deficiency and defects of intermediary glycolytic enzymes). Some defects of the mitochondrial respiratory chain are also associated with myoglobinuria, notably deficiency of CoQ10 (especially related to ETF-DH deficiency) and mutations in the MTCOB gene (Andreu et al. , 1999), but in most cases neither high creatine kinase nor myoglobinuric episodes are frequent symptoms of mitochondrial disorders. In addition, little, if any, attention is paid to the quantitative and qualitative features of therapeutic physical training (van der Kooi …