The purpose of the research study is to evaluate different cardiac measures that are obtained by echocardiographic tests in patients with muscular dystrophy.

The research study will include 50 participants aged 8 to 18 years old (before 18th birthday) with Duchenne, Becker, or autosomal recessive limb-girdle (specifically: LGMD 2C-2F and 2I) muscular dystrophies.

Participants will be seen in one of five Cooperative International Neuromuscular Research Group (CINRG) centers located in the United States.

All study assessments will be completed in the same day and include reviewing past medical and surgical history, collecting vital signs, collecting cardiac measures through echocardiographic tests.

Inclusion Criteria:

• Participants must be between the ages of 8 and 18 years old
• Confirmed diagnosis of muscular dystrophy (DMD, BMD, or LGMD 2C-2F and 2I)

Exclusion Criteria:

• Investigator assessment of inability to comply with protocol
• History of a congenital cardiac defect or other cardiac disease unrelated to muscular dystrophy

8 to 18 years old Confirmed diagnosis of Duchenne, Becker, or autosomal recessive limb-girdle muscular dystrophy (LGMD: 2C-2F and 2I)