This is tough problem because to answer it one has to have the ability to do multiple sampling, i.e, take tissue from different muscles at distal or proximal levels for the limb considered dominant and its contralateral one. Alternatively, a non-invasive technique would need to be applied. In tennis players, selected areas of the ulna or radius in the dominant arm might have up to twice the Bone Mineral Content (BMC). This question could be answered thanks to DEXA or other non-invasive radiographic techniques. But for muscle protein is more challenging. - I think this is an interesting question that could be first approached in an animal model assuming limb dominance is found in experimental animals and such dominance is not mainly related to CNS neurological skill but rather and as in tennis players, to the structure or mass of the limb. Thus, multiple tissue sampling could be done as it is the gold standard technique and it could be compared to imaging and non-invasive techniques.