Skeletal muscle fibers from WT mice were prepared as described (1 (link)). Briefly, a discrete section of isolated fibers were exposed to fluo-5N (1 mM) and RyR blocker ryanodine (50 µM). Fibers were then mechanically skinned and placed in a physiological solution containing 500 nM ERTY and incubated for 30 min at 37 °C. The solution was then replaced with a standard solution with 100 nM Ca2+ (no ERTY) and imaged on an Olympus FV1000 confocal microscope. ERTY fluorescence signal and temperature have been calibrated previously, with the signal changing at 3.9% per 1 °C (50 (link)).