[Ivan Juki? is finishing his Master's degree at the University of Zagreb, Croatia where he also works as a personal trainer and S&C coach for soccer. He is currently an Applied Sport Science Intern at Athletic Lab.] Training variations are essential because they stimulate recovery and adaptation, the avoidance of overtraining, long-term phase potentiation, and an elevation in performance outcomes (Plisk & Stone, 2003). Variation can be introduced into a periodized training program in many ways. Some typical examples of training variations that can be employed when designing a periodized program are manipulations of the overall training load, number of sets, number of repetitions, set configurations, and the exercises selected. These potential methods for introducing training variation allow the strength and conditioning professional a means for introducing novel stimuli into the training program. Hodges et al. (2005) suggest that the introduction of novel stimuli allows a more rapid gain in performance and that the more familiar the individual is with the task, the slower the overall gains in performance are. Therefore, it is essential that the strength and conditioning professional employs variations in the overall training program design in order to maximize the training outcomes. This is especially true for advanced and elite athletes. One often overlooked method of employing variation to the training program is the manipulation of the structure of the set being employed. Traditionally, the configuration of a set requires the athlete to perform each repetition in a continuous fashion where no rest is taken in between each repetition of the set (Fleck & Kraemer, 1997; Haff et al, 2003; Stone & O Bryant, 1987). Cluster loading, sometimes termed inter-repetition rest training, describes a training system whereby the rest periods are manipulated, [...]