Determining what is meant by a set not to failure can be difficult. In one of the studies discussed previously (Izquierdo et al. 2006), athletes experienced in weight training performed their normal periodized training for 16 weeks. For the first six weeks “not failure” was defined as performing six sets of five repetitions at a 10RM resistance in the bench press and the same number of sets and repetitions in the squat using 80% of 10RM. In weeks 7 to 11 it was defined as performing six sets of three repetitions at 6RM in the bench press and the same number of sets and repetitions at 80% of 6RM in the squat. During weeks 12 to 16, both “to failure” and “not to failure” training consisted of a peaking phase consisting of using 85 to 90% of 1RM or approximately 5RM and performing three sets of two to four repetitions per set.
In another study (Izquierdo-Gabarren et al. 2010) in which rowers were trained for eight weeks, “sets to failure” consisted of performing four sets at initially 10 repetitions per set at 75% of 1RM and progressing to four repetitions per set at 92% of 1RM. “Sets not to failure” was defined in two different ways: initially performing four sets of five repetitions per set and progressing toward two repetitions per set at the same intensities as the “to failure” training, or performing only two sets for the same number of repetitions at the same intensities as the “to failure” training.
The first study resulted in similar gains in strength using both “to failure” and “not to failure” training, but greater gains in local muscular endurance with training to failure and greater gains in power with training not to failure. The second study showed greater increases in maximal strength and power when four sets were performed not to failure compared to two sets not to failure. Interestingly, both the four-set and two-set “not to failure” training resulted in significantly greater increases in rowing power in 10 maximal strokes or over 20 minutes of rowing than training to failure did.
In both of these studies, “not to failure” training generally consisted of performing half of the repetitions per set as the “to failure” training. Yet in both studies “not to failure” training resulted in greater increases in some measure of power, and similar or greater increases in strength. This indicates that athletes performing other types of training may not need to carry sets to failure to bring about increases in performance.