International Journal of Sports Physiology and Performance, 2014, 9, 637-642 http://dx.doi.org/10.1123/IJSPP.2013-0246 © 2014 Human Kinetics, Inc. Performance of Maximum Number of Repetitions With Cluster-Set Configuration Eliseo Iglesias-Soler, Eduardo Carballeira,Tania Sanchez-Otero, Xian Mayo, and Miguel Fernandez-del-Olmo Purpose: To analyze performance during the execution of a maximum number of repetitions (MNR) in a cluster-set configura- tion. Method: Nine judokas performed 2 sessions of parallel squats with a load corresponding to 4-repetition maximum (4RM) with a traditional-training (TT) and cluster-training (CT) set configuration. The TT consisted of 3 sets of repetitions leading to failure and 3 min of rest between sets. In the CT the MNR was performed with a rest interval between repetitions (45.44 ± 11.89 s). The work-to-rest ratio was similar for CT and TT. Results: MNR in CT was 45.5 ± 32 repetitions and was 9.33 ± 1.87 times the volume in TT. There was a tendency for the average mean propulsive velocity (MPV) to be higher in CT (0.39 ± 0.04 vs 0.36 ± 0.04 m/s for CT and TT, respectively, P - .054, standardized mean difference [d] = 0.57). The average MPV was higher in CT for a similar number of repetitions (0.44 ± 0.08 vs 0.36 ± 0.04 m/s for CT and TT, respectively, P = .006, d = 1.33). The number of repetitions in TT was correlated with absolute 4RM load (r = -.719, P = .031) but not in CT (r = -.273, P = All). Conclusions: A cluster-set configuration allows for a higher number of repetitions and improved sustainability of mechanical performance. CT, unlike TT, was not affected by absolute load, suggesting an improvement of training volume with high absolute loads. Keywords: resistance training, interrepetition rest, muscle endurance, work-to-rest ratio, mechanical performance Adaptation to resistance training is mediated by the interaction between mechanical, hormonal, and metabolic stimuli.12 Several training variables such as load, volume (sets x repetition), frequency of training, speed of contraction, work-to-rest ratios, or time under tension have a direct influence on the magnitude of these stimuli.3 These variables are interdependent, so an increment of one factor can decrease another variable. In this regard the relationship between the number of repetitions performed in each set and the maximum possible number of repetitions (MNR) is an important factor that is associated with intensity, volume, and metabolic response to a workload.45 It has been shown that traditional set configuration with repetitions leading to failure results in a decline in mechanical performance.6 This requires long rest periods to sustain the number of repetitions in successive sets5 or reductions in the training load to maintain the initial number of repetitions.7 8All these acute effects decrease both the mechanical stimuli and the volume of the session (load x repetition x load). An alternative set configuration consists of manipulating work and rest periods by breaking sets into small clusters of repetitions. This type of training has been termed cluster training (CT), interrepetition rest training, or intraset rest loading.9-'2 The theoretical basis of cluster-set configuration lies in the short rest periods between clusters of repetitions, allowing replenishment of muscle phosphocreatine, improving the quality of each effort and of subsequent training adaptation." In this regard, previous studies have shown that CT involves higher sustainability of mechanical performance,1012-14 improved technique in complex resistance exercises,15 and reduced metabolic demand.2-14 The authors are with the Dept of Physical Education and Sports, University of A Coruna, A Coruna, Spain. Address correspondence to eliseo@udc.es. A question that must be clarified regarding CT is the MNR that can be completed before failure. This issue is of interest since the volume of repetitions has been proposed to be the main variable mediating adaptation to resistance exercise.16-'8 To our knowledge, only 1 study19 has analyzed MNR with cluster-set configuration. That work suggested that employment of 30 seconds of rest between repetitions can be used to reach a high volume (repetitions) and a high intensity (90% 1RM) during the performance of bench press and unilateral biceps curl. However, that study also showed high intersubject variability for the MNR, with coefficients of variation of 50.6% and 69.3% for bench press and biceps curl, respectively. This variability could be explained by the different individual recovery capacities and the duration of pauses between repetitions. Adjusting the pauses between repetitions to the individual recovery capacity could result in a less variable MNR during a CT protocol. Although most of the studies that have compared CT with traditional training (TT) protocols equated both load and exercise-to-rest ratio between conditions,12’20 rest intervals were the same for every subject. One procedure that can be used to individualize the pauses between repetitions is to use the volume completed during successive sets of repetitions until failure as a reference and to then distribute the total time of rest between repetitions.14 Hence, the work-to-rest ratio during CT is the same, but the rest interval between repetitions is adjusted for every subject according to individual muscle endur- ance. To our knowledge only 1 previous study individualized the rest pause in CT, addressing the number of repetitions performed in a TT.14 Those authors showed that CT allowed athletes to increase velocity compared with TT when the number of repetitions and total resting time were equated between conditions. However, the total volume that could be performed in CT was not assessed. Therefore, the main goals of this study were to assess MNR in a cluster-set configuration when pauses are fixed in reference to 637