, 2002; Rooney et al., 1994), fatigue has been suggested to interfere with the development of muscular power output (Tidow, 1990). Indeed, the insertion of short inter-repetition rest periods (20 �C 130 s) during cluster sets has been shown to ameliorate the decrease in bar velocity and power output between repetitions completed in sets of TSA both clean pulls and the bench press exercise compared to a continuous repetitions scheme (Denton and Cronin, 2006; Haff et al., 2003; Lawton et al., 2006). Furthermore, the advantage of short inter-repetition rest periods in maintaining power output during the bench press exercise appears to be unrelated to the specific configuration used, with schemes involving singles and doubles being equally effective (Lawton et al., 2006).

Most of the studies investigating the use of cluster sets with resistance exercises have focused on the mechanical variables of bar velocity and power output (Denton and Cronin, 2006; Haff et al., 2003; Lawton et al., 2006). These variables do not provide sufficient information for the strength and conditioning practitioner to determine the potential efficacy of cluster sets given the potential mechanical stimuli (e.g. force, impulse, work, power output) that are proposed to be important in the neuromuscular adaptations accrued from a period of resistance training (Crewther et al., 2005). Despite recent researchers including other mechanical variables (e.g. impulse, work (Denton and Cronin, 2006)), all of these studies are limited by the use of technologies that preclude the measurement of the ground reaction force during the movement, bringing the validity of the data into question (Cormie et al.

, 2007; Crewther et al., 2011). Therefore, the purpose of the present study was to investigate the effects of different configurations of repetitions within a set of deadlifts on the mechanical variables of force, impulse, work, power, concentric time and fatigue recorded using force platforms and a motion analysis system. Material and Methods The study employed a crossover design in which subjects were required to perform four repetitions of the deadlift exercise with a load equivalent to 90% of 1-repetition maximum (1RM) under three different set configurations: Traditional set, where the repetitions were performed continuously; Doubles cluster set, where repetitions 1 and 2, and 3 and 4 were performed continuously with a 30 s rest inserted between repetitions 2 and 3; Singles cluster set, where 30 s rest was provided between each consecutive repetition.

Each set configuration was performed during a separate testing session separated by a minimum of GSK-3 72 hours and the order in which the sessions were administered was counterbalanced across the subjects. Participants Eleven men agreed to participate in the present study (age: 21.9 �� 1.0 years; body height: 1.82 �� 0.08 m; body mass: 94.1 �� 19.4 kg; deadlift 1-RM: 183.