IGF1 and sarcopenia: Although the study of sarcopenia is complicated by muscle-specific differences among species and in the response to aging (41), there is consensus that anabolic stimuli do not efficiently activate the IGFI/PI3K/Akt/PKB/mTORC1 pathway (displayed in Figure 1) in elderly people, and this anabolic resistance is believed to play a major role in causing sarcopenia and reduced muscle recovery after an injury (41).