Studies of the carrier state in the Duchenne type of muscular dystrophy. I. Effect of exercise on serum creatine kinase activity.

The value of estimating the activities of various serum enzymes, particularly creatine kinase (CK) in confirming the diagnosis of the Duchenne type of progressive muscular dystrophy and in detecting the disease in apparently unaffected younger male sibs of known cases is well established (Chung, Morton, and Peters, 1960; Aebi, Richterich, Stillhart, Colombo, and Rossi, 1961; Pearce, Pennington, and Walton, 1964a). Measurement of serum creatine kinase activity has also been advocated for the diagnosis of the carrier state (Dreyfus, Schapira, and Demos, 1960; Aebi, Richterich, Colombo, and Rossi, 1962; Hughes, 1962; Pearce, Pennington, and Walton, 1964b; Wilson, Evans, and Carter, 1965; Walton and Pennington, 1966) but the rise in serum activity is only slight in the majority of cases and it has recently been shown (Vejjajiva and Teasdale, 1965; Griffiths, 1966) that prolonged strenuous exercise will produce such a rise in normal subjects, though Pearce, Pennington, and Walton (1964c) found no such rise after a short period of moderate exertion. On the other hand, Stephens and Lewin (1965) described three carrier females in whom the serum creatine kinase activity, which was raised during everyday activity, fell to normal after complete bed rest and rose again after exertion. In a further possible carrier the activity in a random serum sample was normal but strenuous exertion again provoked a rise. The purpose of this study was twofold: (1) to determine whether or not a standardized programme of exercise of moderate severity had any effect on serum creatine kinase activity in normal young women; (2) to see if the same standard exercise produced any change in the serum enzyme activity in a group of definite or suspected carriers of Duchenne dystrophy previously shown to have normal serum enzyme levels (Pearce et al., 1964b). It was hoped that a creatine kinase after exercise/creatine kinase after bed rest ratio