In addition, GH stimulates the IRS1/Akt (Costoya et al., 1999; Consitt et al., 2017) and mitogen-activated protein kinase (MAPK) pathways which are thought to be the main pathways contributing to GH/IGF-1-induced muscle hypertrophy via p42/p44 and p38 pathways (Consitt et al., 2017) (Figure 1). It was reported that there is a correlation between acute RE-induced GH increases and long term muscle and fiber type I and II hypertrophy (McCall et al., 1999). In younger adults, exercise-induced GH release is relatively non-specific occurring in response to both RE and aerobic exercise (e.g., 60% VO2 max) (Godfrey et al., 2003). These increases in post RE GH levels are blunted in older adults, and a progressive decline in GH secretion and clearance is observed after the age of 40 y (Zaccaria et al., 1999).