The severity of the disease in patients with autosomal dominant MYH2 was related to the amount of expressed MyHC IIa protein in muscle. Severely affected individuals and muscles showed a large proportion of type 2A muscle fibers, and the fibers with rimmed vacuoles expressed MyHC IIa. Studies on the effects of endurance training have been performed. An 8-week endurance training program on a stationary exercise bicycle had no adverse effects. The peak watt and walking speed increased, but there was no significant increase in muscle strength or isometric endurance. The training program resulted in a shift in expression from fast to slow MyHC isoforms. There was no significant change in the MyHC IIa expression, but frequent hybrid fibers expressing more than one MyHC isoform were identified.
MYH2