The total volume of a resistance exercise is determined by multiplying the number of repetitions by load. Although the results of both studies are important to the understanding of the effects of RI on number of repetitions and sustainability, such findings cannot be applied to older adults or to lower-limb performance, due to differences related to the aging process (e.g., decrease of muscle quality, fatigue, and muscle recovery) (Bottaro et al., 2010 Lynch et al., 1999). In resistance-trained older women, Jambassi Filho et al., 2010 observed similar behavior when comparing two RI (1.5 and 3 minutes) during an arm curl exercise. The longer RI promoted a greater number of repetitions as compared to the shorter RI. Willardson and Burkett, 2006b concluded that, in resistance-trained young adults, different RI (0.5, 1, and 2 minutes) did not promote the sustainability of repetitions in multiple sets of the squat and bench press.
The potential effect of RI, between sets, on acute muscle performance in single resistance training exercises, has been demonstrated in young and older adults (Jambassi Filho et al., 2010 Willardson and Burkett, 2006a 2006b). The effectiveness of a resistance training program depends on several acute variables, such as intensity, volume, weekly frequency, movement velocity, exercise order, and duration of the rest interval (RI) between sets and exercises (ACSM, 2009). Progressive resistance training exercises are designed to improve neuromuscular performance, physical function, quality of life, and to prevent and treat chronic diseases in older adults (Hurley et al., 2011 Katula et al., 2008 Tschopp et al., 2011). The longer RI should be used, therefore, when the goal of training is to increase the total volume. The length of the RI between sets influenced the number of repetitions, sustainability of repetitions, and total volume. The total volume for the RI-3 session was statistically higher (29.4%, p < 0.05) as compared to the RI-1 session. Differences (p < 0.05) between the RI also were observed in the two final sets. For both RI, significant reductions (p < 0.05) were observed in the number of repetitions and sustainability of repetitions, from the first to the second and third sets. In each session, one of two RI (one-minute: RI-1 and three minute: RI-3) was tested, employing a randomized and counterbalanced design. All participants performed three sets to voluntary exhaustion, with loads that corresponded to 15 maximum repetitions, in two experimental sessions (that ranged from 48 to 72 hours apart).
Seventeen resistance-trained older women (68.0 ± 5.9 years, 71. The purpose of this study was to assess the effect of different rest intervals (RI) between sets on number of repetitions, sustainability of repetitions, and total volume during a leg press exercise.