Preclinical research and development for muscular dystrophies has historically been hindered by a reliance on animal models that often fail to fully replicate human biology. This translational gap is a key contributor to the high clinical trial failure rate. Human in vitro cellular models enable testing in human cell environments, however, widespread adoption in the field has been slowed by limited translational phenotypes observed in the dish. Traditional 2D muscle cultures are plagued with developmental obstacles, such as random cellular organization, limited culture times, and immature developmental states. Moreover, contractile force measurements are largely impossible in 2D, limiting the ability to robustly stratify disease-relevant phenotypes. Engineering muscle tissues in 3D provides a solution to many of these limitations however, rigorous quality control is critical to ensure optimal tissue function. Our data show that contractile force declines with increasing myoblast passages in 3D engineered muscle tissues (EMTs), indicating myoblast purity and health may directly impact muscle performance. Furthermore, we show that addition of stromal cells into EMTs, combined with electrical stimulation on the Mantarray™ contractility platform, improves and stabilizes contractile force and increases functional longevity of the muscle. Increased levels of adult protein isoforms in these constructs suggest enriched maturation, providing a more physiologically relevant human model. We also stretch these tissues under load to model eccentric contractions and muscle injury. We show increased levels of creatine kinase, a biomarker of cellular damage. Finally, we developed a method to suspend EMTs in a commercially available gel that permits transfer of tissues between labs under ambient storage conditions. Tissues remain viable and fully functional upon gel dissolution for direct interrogation with therapeutic compounds, eliminating the need to fabricate 3D tissues in-house. These improved culturing methods and technologies offer a highly scalable and translatable platform for functional potency assessment of numerous therapeutic modalities.