Muscle Activation During Power-Oriented Resistance Training: Continuous vs. Cluster Set Configurations.

This study examined performance and electromyography (EMG) changes during a power training protocol comprising continuous or clustered set configurations. Eighteen active males completed 6 sets of 6 repetitions during the loaded (20% 1 repetition maximum) countermovement jump (CMJ) exercise, continuously (n = 9) or with a 30-second pause every 2 repetitions (cluster; n = 9). Power output, vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) EMG were recorded during all CMJs. Relative changes from the first repetition were assessed on the EMG root mean square (RMS), median frequency (F-med), and a low- to high-frequency ratio index of fatigue (FInsmk). Greater power output decrements were observed during the continuous set configuration (p = 0.001, eta(2)(G) < 0.01). Greater RMS increments in VL (6.8 +/- 11.3 vs. -1.7 +/- 5.8%) and RF (9.3 +/- 14.2 vs. 1.9 +/- 6.9%), but not VM (2.0 +/- 4.7 vs. 2.6 +/- 7.3%), were also observed in the continuous compared with the cluster sets (p = 0.033, eta(2)(G) = 0.06). Progressive decrements in Fmed and increments in FInsmk were observed across repetitions in both set configurations. In conclusion, although clustering sets between repetitions clearly maintained power output, mixed responses were observed on the examined EMG parameters.