The aim of the proposed research is to compare two commonly used pediatric strength testing measures: handheld myometry (HHM) and CINRG Quantitative Measurement System (CQMS), with the goal of identifying a sensitive and valid tool for measuring muscle strength in children with DMD. The data obtained from this study will be used to make recommendations for strength measurement endpoints in prospective muscular dystrophy trials and provide more reliable and accurate recommendations in the clinic for strength assessment. This study will be performed at six participating sites in the Cooperative International Neuromuscular Research Group (CINRG).

We propose to compare the reliability of CQMS vs. HHM in the DMD population. The importance of this study is to be able to compare the results of clinical trials done by different networks using distinct strength endpoints. If results indicate a distinct difference in reliability of one tool over the other, a standardized tool could be established for research groups throughout the world to interpret strength in the context of clinical trials. If the results indicate minor differences then it would be possible to interpret and compare/contrast strength measurements used in different studies.

Understanding the relationship between the HHM vs CQMS will help us examine other surrogate measures capable of predicting functionality that are based on strength measurements.

Participants should meet the following criteria:

1. Confirmed clinical and molecular diagnosis of DMD
2. 6- 18 years of age
3. Ability to follow 2 step instructions
4. Ability to transfer to and from the wheelchair-mat with moderate assistance defined as no greater than 75% assistance.
5. Signed informed consent of parental or legal guardian(s) is required for participants. Assent from children 7-18 years old may also required.

Exclusion Criteria:

Participants must confirm:

1. No Surgical procedures were performed ≤ 8 weeks before study procedures.
2. No musculoskeletal injuries were experienced ≤ 8 weeks before study procedures.
3. Investigator assessment that patient or parent/legal guardian are not willing or able to comply with study procedures.

Participants will be selected from participating CINRG institution's neuromuscular clinics.