Effect of Set-Structure on Upper-Body Muscular Hypertrophy and Performance in Recreationally-Trained Male and Female
Davies, Timothy B.; Halaki, Mark; Orr, Rhonda; Mitchell, Lachlan; Helms, Eric R.; Clarke, Jillian; Hackett, Daniel A.
Journal of Strength and Conditioning Research: August 2022 - Volume 36 - Issue 8 - p 2176-2185, doi: 10.1519/JSC.0000000000003971
To explore the effect of 1) volume-equated traditional-set and 2) cluster-set structures on muscular hypertrophy and performance after high-load resistance training in the bench press.
21 subjects (12 men and 9 women) performed a 3-week orientation phase then were randomly assigned to one of two 8-week upper-body and lower-body split programs occurring over 3 and then progressing to 4 sessions per week.
They performed 4 sets of 5 repetitions at 85% one repetition maximum (1-RM) using either a:
1. Traditional-set structure (TRAD) that involved 5 minutes of rest between sets only.
2. Cluster-set structure (CLUS) that included a 30-second rest between each repetition and 3 minutes of rest between sets.
To estimate changes in muscular strength, local muscular endurance, regional muscular hypertrophy, and body composition, a 1-RM bench press, repetitions to failure at 70% 1-RM, regional muscle thickness, and dual-energy x-ray absorptiometry were used.
Velocity loss was assessed using a linear position transducer at the intervention midpoint.
TRAD demonstrated a significantly greater velocity loss magnitude and muscle thickness of the proximal pectoralis major compared with CLUS.
There were no significant differences between groups for the remaining outcomes, although a small effect size favoring TRAD was observed for the middle region of the pectoralis major.
IN PLAIN ENGLISH:
The longer the rest between efforts – whether it’s a single rep or a set of reps – the less fatigue and thus the ability to move a relatively heavy resistance at a faster speed (i.e., recruit the larger and faster type 2X motor units).
All other factors being equal, muscle hypertrophy is triggered due to this sequence:
1. Fatigue occurs.
2. Movement speed slows.
3. The CNS recruits the high threshold and larger type 2X motor units to
continue the task.
4. The end result is greater overall tension is developed in the acting