Pseudoathletic appearance is a medical sign meaning to have the false appearance of a well-trained athlete due to pathologic causes (disease or injury) instead of true athleticism. It is also referred to as a Herculean or bodybuilder-like appearance. It may be the result of muscle inflammation (immunity-related swelling), muscle hyperplasia, muscle hypertrophy, muscle pseudohypertrophy (muscle atrophy with infiltration of fat or other tissue), or symmetrical subcutaneous (under the skin) deposits of fat or other tissue.
The mechanism resulting in this sign may stay consistent or may change, while the sign itself remains. For instance, some individuals with Duchenne and Becker muscular dystrophy may start with true muscle hypertrophy, but later develop into pseudohypertrophy.
In healthy individuals, resistance training and heavy manual labour creates muscle hypertrophy through signalling from mechanical stimulation (mechanotransduction) and from sensing available energy reserves (such as AMP through AMP-activated protein kinase); however, in the absence of a sports or vocational explanation for muscle hypertrophy, especially with accompanying muscle symptoms (such as myalgia, cramping, or exercise intolerance), then a neuromuscular disorder should be suspected.
As muscle hypertrophy is a response to strenuous anaerobic activity, ordinary everyday activity would become strenuous in diseases that result in premature muscle fatigue (neural or metabolic), or disrupt the excitation-contraction coupling in muscle, or cause repetitive or sustained involuntary muscle contractions (fasciculations, myotonia, or spasticity). In lipodystrophy, an abnormal deficit of subcutaneous fat accentuates the appearance of the muscles, though in some forms the muscles are quantifiably hypertrophic (possibly due to a metabolic abnormality).
Neuromuscular disease centre, Washington University - Large or prominent muscles
National Center for Biotechnology Information (NCBI) - Skeletal muscle hypertrophy, generalized muscle hypertrophy, calf muscle hypertrophy, thigh hypertrophy
The Human Phenotype Ontology (HPO) project - Skeletal muscle hypertrophy, calf muscle hypertrophy, muscle hypertrophy of the lower extremities, upper limb muscle hypertrophy