What does Boxing Day have to do with boxing?
myopathy my·op·a·thy (mī-ŏp'ə-thē)
Any of various abnormal conditions or diseases of the muscular tissues, especially one involving skeletal muscle.
any skeletal muscle disorder that directly affects the muscle fibres and does not arise secondarily from disorders of the nervous system. Myopathies are marked by muscular degeneration and weakness and may have a genetic or nongenetic basis