Different Cluster Sets Result in Similar Metabolic, Endocrine, and Perceptual Responses in Trained Men

Tufano, JJ, Conlon, JA, Nimphius, S, Oliver, JM, Kreutzer, A, and Haff, GG. Different cluster sets result in similar metabolic, endocrine, and perceptual responses in trained men. J Strength Cond Res 33(2): 346-354, 2019-The purpose of this study was to compare the kinematic, metabolic, endocrine, and perceptual responses of 3 back squat protocols with equal loads, number of repetitions, and total rest duration. Eight strength-trained men performed 36 back squats using 75% 1 repetition maximum and 420 seconds of total rest during basic cluster sets of 4 (CS4), rest redistribution sets of 4 (RR4), and rest redistribution sets of 1 (RR1). Rating of perceived exertion (RPE), blood lactate (La), mean velocity maintenance (MVM), and mean velocity loss (MVL) were measured during exercise. Total testosterone (TT), growth hormone (GH), cortisol (C), and sex hormone-binding globulin (SHBG) were measured before exercise and 15, 30, and 60 minutes postexercise. There were no differences between protocols for MVM. However, MVL was less during RR1 compared with RR4 (p = 0.032), and neither protocol was different than CS4. All protocols resulted in similar increases in RPE and La, which remained elevated up to 30 minutes postexercise (p ≤ 0.05). In all protocols, GH increased and returned to baseline by 60 minutes postexercise (p ≤ 0.05). At 60 minutes postexercise, TT was less than all other time points (p ≤ 0.05). There were no main effects for time for SHBG or C. The data from this study show that different types of cluster set protocols can result in proanabolic physiological responses to resistance training. In addition, coaches can redistribute rest periods without affecting perceived effort or metabolic and hormonal changes if the external load, number of repetitions, and total rest time are equalized.