The purpose of this study was to examine the effects of different rest interval (RI) lengths on metabolic responses to the bench press. Eight resistance-trained men performed 10 randomized protocols [five sets of bench press with 75 or 85% of 1RM for ten (10REP) and five repetitions (5REP), respectively, using different RI (30 s, 1, 2, 3, 5 min)]. Oxygen consumption (VO(2)) was measured during exercise and for 30 min post exercise. For 30-s and 1-min RI: reductions (15-55%) in resistance and volume were observed (set 5 < 4 < 3 < 2 < 1). For 2-min RI: performance was maintained during the first two sets but was reduced by 8-29% during sets 3-5. For 3-min RI: a reduction was observed in volume where sets 4 and 5 were lower than sets 1-3 ( approximately 21%). For 5-min RI: only a reduction in set 5 was observed. Mean VO(2) and ventilation (V (E)) were progressively higher as RI length was shortened. VO(2) area under the curve indicated 10REP > 5REP for all RI except 1-min. Respiratory exchange ratio (RER) was elevated similarly for each protocol. Post exercise, VO(2), V (E), and RER were elevated through 30 min. No differences between RI were observed following 10REP; however, VO(2) after 30-s was higher than 2-, 3-, and 5-min and 1-min was higher than 5-min during 5REP. Fatigue rate was correlated (r = 0.30-0.49) to all metabolic variables. A continuum of performance reductions and metabolic responses were observed. The largest reductions in performance occurred with very short RI (<1 min), and performance was maintained during the first 3-4 sets when 3- and 5-min RI were used.

This investigation compared the effect of high-volume (VOL) versus high-intensity (INT) resistance training on stimulating changes in muscle size and strength in resistance-trained men. Following a 2-week preparatory phase, participants were randomly assigned to either a high-volume (VOL; n = 14, 4 × 10–12 repetitions with ∼70% of one repetition maximum [1RM], 1-min rest intervals) or a high-intensity (INT; n = 15, 4 × 3–5 repetitions with ∼90% of 1RM, 3-min rest intervals) training group for 8 weeks. Pre- and posttraining assessments included lean tissue mass via dual energy x-ray absorptiometry, muscle cross-sectional area and thickness of the vastus lateralis (VL), rectus femoris (RF), pectoralis major, and triceps brachii muscles via ultrasound images, and 1RM strength in the back squat and bench press (BP) exercises. Blood samples were collected at baseline, immediately post, 30 min post, and 60 min postexercise at week 3 (WK3) and week 10 (WK10) to assess the serum testosterone, growth hormone (GH), insulin-like growth factor-1 (IGF1), cortisol, and insulin concentrations. Compared to VOL, greater improvements (P < 0.05) in lean arm mass (5.2 ± 2.9% vs. 2.2 ± 5.6%) and 1RM BP (14.8 ± 9.7% vs. 6.9 ± 9.0%) were observed for INT. Compared to INT, area under the curve analysis revealed greater (P < 0.05) GH and cortisol responses for VOL at WK3 and cortisol only at WK10. Compared to WK3, the GH and cortisol responses were attenuated (P < 0.05) for VOL at WK10, while the IGF1 response was reduced (P < 0.05) for INT. It appears that high-intensity resistance training stimulates greater improvements in some measures of strength and hypertrophy in resistance-trained men during a short-term training period.

Recently, interest in time-restricted feeding (TRF) has increased from reports highlighting improvements in body composition and muscular performance measures. Twenty-six recreationally active males were randomly assigned to either TRF (n = 13; ~22.9 years; 82.0 kg; 178.1 cm; 8 h eating window, 25% caloric deficit, 1.8 g/kg/day protein) or normal diet (ND; n = 13; ~22.5 years; 83.3 kg; 177.5 cm; normal meal pattern; 25% caloric deficit, 1.8 g/kg/day protein) groups. Participants underwent 4-weeks of supervised full body resistance training. Changes in body composition (fat mass (FM), fat free mass (FFM), and body fat percentage (BF%)), skeletal muscle cross sectional area (CSA) and muscle thickness (MT) of the vastus lateralis (VL), rectus femoris, (RF), and biceps brachii (BB) muscles, resting energy expenditure (REE), muscular performance, blood biomarkers, and psychometric parameters were assessed. Significant (p < 0.05) decreases were noted in BM, FM, BF%, testosterone, adiponectin, and REE, along with significant increases in BP1RM, LP1RM, VJHT, VJPP, VLCSA, BBCSA, and BBMT in both groups. Plasma cortisol levels were significantly elevated at post (p = 0.018) only in ND. Additionally, FFM was maintained equally between groups. Thus, a TRF style of eating does not enhance reductions in FM over caloric restriction alone during a 4-week hypocaloric diet.

Changes in muscle architecture appear to occur in a non-homogeneous manner.

The effects of creatine and creatine plus beta-alanine on strength, power, body composition, and endocrine changes were examined during a 10-wk resistance training program in collegiate football players. Thirty-three male subjects were randomly assigned to either a placebo (P), creatine (C), or creatine plus beta-alanine (CA) group. During each testing session subjects were assessed for strength (maximum bench press and squat), power (Wingate anaerobic power test, 20-jump test), and body composition. Resting blood samples were analyzed for total testosterone, cortisol, growth hormone, IGF-1, and sex hormone binding globulin. Changes in lean body mass and percent body fat were greater (P < 0.05) in CA compared to C or P. Significantly greater strength improvements were seen in CA and C compared to P. Resting testosterone concentrations were elevated in C, however, no other significant endocrine changes were noted. Results of this study demonstrate the efficacy of creatine and creatine plus beta-alanine on strength performance. Creatine plus beta-alanine supplementation appeared to have the greatest effect on lean tissue accruement and body fat composition.