How are the mice able to resist muscle frailty?
The mice were genetically engineered to overproduce a protein called muscle insulinlike growth factor 1 (mIgf1, for short). The protein is normally produced by young, healthy muscles, and it stimulates muscle growth and regeneration. Boosting mIgf1 levels in the mice made them more muscular throughout life, and, in old age, it enabled them to recover from muscle injuries that would have normally caused permanent damage.
