In order to examine the effects of different rest intervals between the sets on acute growth hormone (GH) and insulin-link growth factor-1 (IGF-I)responses, ten recreationally resistance men served as subject (Mean ±SD , age=22± 2 years, body mass= 84 ±8 kg). Subjects performed tow heavy-resistance training protocols that were similar with regard to the total volume of work (sets x reps x loads), but differed with regard the length of reset between sets (1vs.3-minutes). Both protocols included 5 sets of 10 RM bench press and squat that performed on tow randomized separate session. Blood samples were collected before, immediately after and 1-hour after the protocols for determination GH, IGF-I and blood lactate concentration. Post exercise values for lactate and GH were significantly (P <= 0.05) elevated above preexercise, but did not for IGF-1 serum concentrations were significantly (P<= 0.05) increased during 1-hour post-exercise. Post exercise serum GH and blood lactate concentrations were significantly (P<= 0.05) higher in SR than LR protocol, but IGF-1 did not change. These data suggest that the duration of the rest interval between sets of dynamic resistance exercise influence GH serum concentration, in must be noted that short rest period between sets induced greater acute GH responses than the long rest period. Given that GH concentration is an anabolic hormone, this finding may have implications regarding hypertrophy in resistance training.
