Ryanodine and calstabin are important molecules regulating calcium flow in skeletal muscles. Calcium is critical for muscle contractions and depletion of calstabin results in calcium leakage that can reduce endurance and muscle contractile strength. Stabilization of calstabin with small molecules like S-107 or JTV-519 results in improved endurance and increased strength. These drugs are still in the development stage but are already on the radar of anti-doping agencies. Very little is known about these molecules and the pathways they regulate are still poorly understood.