(A) Measurements of in vivo resting [Ca2+]i and [Na+]i in skeletal muscle and (B) similar measurement in vitro in isolated muscle fibres. In both preparations, both resting [Ca2+]i and [Na+]i were significantly different between each other and both were significantly different than control. P<0.001. [Ca2+]i, intracellular calcium; [Na+]i, intracellular sodium; MH, malignant hyperthermia; MHN, MH normal; MHS-Hom, homozygous MHS; MHS-Het, heterozygous MHS.