Thin filament characteristics and myofilament performance. A. Normalized isometric tension-calcium relationships of HG and nonHG controls were not different from each other, indicating similar thin filament sensitivities to calcium activation. B. Native thin filament (NTF) velocity-calcium relationships detected using the myosin motility assay were also similar between HG and nonHG demonstrating similar calcium sensitivity and myosin-actin MgATPase activity. Inset illustrates that HG did not affect NTF function in euthyroid rats not PTU-treated.