The Effect Of Traditional And Cluster Set Configurations On Muscle Strength And Size In Trained Subjects

PURPOSE: The purpose of this study was to examine adaptations in maximal voluntary isometric contraction (MVIC) strength and thigh circumference prior to (PRE), after 2 weeks (MID), and four weeks (POST) of resistance training (RT) involving traditional (TRAD) and cluster (CL) training protocols. METHODS: Seventeen resistance trained males (8 F/9 M) participated in this 4-week intervention. Each subject had their lower limbs randomized to TRAD or CL set configurations, which were matched for work and time. The TRAD protocol was completed first during each session, in which subjects completed 4 sets to ≥8 RPE with 2 minutes of rest of leg extension and leg curl exercise. The CL leg completed the same amount of work with the rest period interspersed around clusters of 1-3 repetitions. Thigh circumference, measured via Fit3D, and knee extension MVIC strength at 90° of knee flexion were measured on each leg at PRE, MID, and POST. Separate condition (TRAD/CL) x sex (M/F) x time (PRE/MID/POST) ANOVAs were used to examine each variable. Post-hoc tests were conducted to examine significant effects and the alpha level was set a-priori at 0.05. RESULTS: There was no significant time × condition interaction (p = 0.411-0.504) or main effects for time (p = 0.061-0.296) for either variable. However, there was a main effect for sex for MVIC strength (p < 0.001), in which post-hoc analyses indicated that males had significantly greater MVIC strength than females, (p < 0.001; M: 57.6 ± 16.2 kg; F: 47.5 ± 6.7 kgs) when collapsed across all other factors. CONCLUSIONS: Our data indicates that 4-weeks of TRAD or CL leg extension did not significantly alter thigh circumference or MVIC strength of the knee extensors in trained subjects. However, due to the large variability in responses, particularly in MVIC strength (95% CIs for ΔPOST-PRE; TRAD: -1.4-10.1 kg vs. CS: -5.0-3.2 kgs), further investigation is warranted to examine the underlying factors associated with the inter-subject variability.