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Observational studies have shown correlations between intramyocellular lipid (IMCL) content and muscle strength and contractile function in people with metabolically abnormal obesity. However, a clear physiologic mechanism for this association is lacking, and causation is debated. We combined immunofluorescent confocal imaging with force measurements on permeabilized muscle fibers from metabolically normal and metabolically abnormal mice and people with metabolically normal (defined as normal fasting plasma glucose and glucose tolerance) and metabolically abnormal (defined as prediabetes and type 2 diabetes) overweight/obesity to evaluate relationships among myocellular lipid droplet characteristics (droplet size and density) and biophysical (active contractile and passive viscoelastic) properties. The fiber type specificity of lipid droplet parameters varied by metabolic status and by species. It was different between mice and people across the board and different between people of different metabolic status. However, despite considerable quantities of IMCL in the metabolically abnormal groups, there were no significant differences in peak active tension or passive viscoelasticity between the metabolically abnormal and control groups in mice or people. Additionally, there were no significant relationships among IMCL parameters and biophysical variables. Thus, we conclude that IMCL accumulation per se does not impact muscle fiber biophysical properties or physically impede contraction. Article Highlights: Excess intramyocellular lipid (IMCL) could physically disrupt sarcomere contraction by pushing myofibrils apart, increasing myofilament stiffness, or changing cytoplasmic viscoelasticity. We used isolated, permeabilized myofibers from metabolically normal and metabolically abnormal mice and people with metabolically normal and abnormal obesity to evaluate the relationships among IMCL lipid droplet characteristics and myofiber mechanics. We found fiber type–specific differences in IMCL accumulation among species and metabolic status but no relationships among any IMCL parameters and myofiber biophysical properties. If IMCL directly impairs muscle contraction, it is not through physical disruption of sarcomeres or cytoplasmic composition. [ABSTRACT FROM AUTHOR]