Relationship between limb and trunk muscle hypertrophy following high-intensity resistance training and blood flow-restricted low-intensity resistance training

We examined the relationship between training-induced limb and trunk muscle hypertrophy in high-intensity resistance training (HIT) or blood flow restricted low-intensity resistance training (LI-BFR) programmes. Thirty young men were divided into three groups: HIT (n = 10), LI-BFR (n = 10) and non-training control (CON, n = 0). The HIT and LI-BFR groups performed 75% and 30%, respectively, of one-repetition maximal (1-RM) bench press exercise, 3 days per week for 6 weeks. During the training sessions, the LI-BFR group wore elastic cuffs around the most proximal region of both arms. Muscle cross-sectional area (CSA) and 1-RM bench press strength were measured before and 3 days after the final training session. Total training volumes (lifting weight X number of repetitions) for all of the sessions were similar between the two training groups. The training led to a significant increase (P < 005) in bench press 1-RM in the two training groups, but not in the CON group. Triceps brachii and pectoralis major muscle CSA increased 8-8% and 15-8% (P < 0.01), respectively, in the HIT group and 4-9% (P < 0.05) and 8-3% (P < 0.01), respectively, in the LI-BFR group, but not in the CON group (-1.1% and 0.0%, respectively). There was significant correlation (r = 0.70, P < 0.05) between increases in triceps brachii and pectoralis major muscle CSA in the HIT group; however, the correlation was lower and non-significant in the LI-BFR group (r = 0.54). Our results suggest that limb and trunk muscle hypertrophy occurs simultaneously during HIT but not during LT-BFR, possibly owing to individual differences in activation of the arm and chest muscles during the training sessions.