The main finding of the present study was that two-minute rest intervals resulted in significantly lower repetitions performed for all the exercises in the second set compared with the first one, except for PD, and for the third set compared to the first and second set, except for LE. For five-minute, the declines in repetitions were only significant for LP, LC and TP exercises in the third set. Additionally, the total number of repetitions for all the exercises and the total number of the repetitions in the sessions showed significantly reduced values in SEQA and SEQC (sessions with two-minute intervals between sets and exercises). Miranda et al., 2007 found similar results to the present study when comparing the effects of one and three-minute rest intervals on the number of repetitions per sets, total volume of each exercise and total volume of the training session. In the above-mentioned study, 14 trained men performed two training sessions, consisting of three sets with 8RM loads, in six exercises for upper body, in the following order: lat pull-down with a wide grip, lat pull-down with a close grip, machine seated row, barbell row lying on a bench, dumbbell seated arm curl and machine seated arm curl. The two experimental sessions differed only in the rest interval between sets and exercises (one and three-minute). For all the exercises, the results showed a lower total number of repetitions when one-minute intervals were used. Both protocols resulted in significant reductions in the third set compared with the first set, in four of the six exercises. Moreover, the protocol that used one-minute also showed reductions in the second set compared with the first set, in two of the six exercises. Although using different intervals and exercises, the results of this study are similar to ours, by showing that shorter rest intervals between sets and exercises can result in declines on the total volume of repetitions of a training session. Additionally, the results of Miranda et al., 2007 showed tendencies towards more substantial reductions in the number of repetitions of the exercises performed at the end of the sequences, which can also be observed in our results Simão et al., 2005 investigated the influence of different exercise sequences on the number of repetitions performed in a group composed of both trained men and women. The exercise sessions, consisted of performing three sets of each exercise with a resistance of 10RM and two-minute rest periods between sets and exercises. The results demonstrated performing either large or small group exercises for the upper- body at the end of an exercise sequence resulted in significantly fewer repetitions, compared to when the same exercises were performed early in an exercise sequence. A more recent study by Simão et al., 2007 demonstrated a similar phenomenon in trained women when both upper and lower-body exercises were performed in the same exercise session. Like described by Simão et al. (2005; 2007), utilized 2- minute rest are used, reduced numbers of repetitions (approximately eight) were observed even at the first set of the exercises performed last (LE, LC and PD). These results can be associated to the progressive fatigue accumulation during the progression of the sets and exercises in the training session, as observed in previous studies (Simão et al., 2005; 2007). Previous studies seem to be convergent regarding the rest interval influence between sets on the number of repetitions during the progression of the sets in the same exercise (Rahimi, 2005; Willardson and Burkett, 2005; 2006a; 2006b). Ratamess et al., 2007 examined the effects of different rest intervals on the intensity, volume, and metabolic responses to the bench press exercise. Eight trained men performed 10 randomized protocols [five bench press sets at 75% or 85% of 1RM for 10 repetitions and five repetitions, respectively, using different intervals between sets (30 seconds, one-, two-, three, five-minute)]. The oxygen consumption was measured during exercise and for 30 minutes thereafter. For the 30 second and 1 minute rest intervals, 15-55% reductions in intensity and volume were observed (sets five < four < three < two < one). For the two-minute rest interval, the performance was maintained during the first two sets, but declined 8-29% during the third, fourth and fifth sets. For the three-minute rest interval, a volume reduction was noted for the fourth and fifth sets, (approximately 21% lower than the first, second, and third sets). At five-minute, a reduction was observed only for the fifth set. Overall, the greatest reductions in performance occurred with very short rest intervals (< one-minute), and performance was maintained during the first three to four sets when three to five-minute rest intervals were utilized. Confirming this, our results showed that longer rest intervals of five-minute enabled a significantly increased number of repetitions per exercise, when compared with two-minute. Abdessemed et al., 1999 associate the decrease in the total number of repetitions with the concomitant effects of the lactate accumulation and insufficient time for a complete creatine phosphate (CP) store resynthesis. Knowing that the strength performance is highly dependent of the anaerobic energetic metabolism (especially ATP-PC), rest interval length in each exercise or session, determines fatigue development. Thus, it can be stated that periods with varied lengths between sets and exercises effectively result in different physiological responses, which causes an impact in resistance training programs, according to the aimed objective (Abdessemed et al., 1999). Our results or the results obtained by Miranda et al., 2007 showed that longer intervals allow the sustainability of the number of repetitions in sets and subsequent exercises performed in a same training session, exerting direct effect on the total training volume (Willardson and Burkett, 2008). On the other hand, shorter rest intervals can result in favorable hormonal and metabolic responses to a training session (Bottaro et al., 2009). Bottaro et al., 2009 investigated the acute hormonal responses to three distinct intervals between sets in similar resistance training sessions involving exercises for lower body. This study composed three resistance training sessions performed by 12 trained women, with 30, 60 and 120 seconds intervals between sets and exercises. The training sessions consisted of four exercises for lower body, performed up to muscular concentric failure, in three sets with 10RM loads. No difference was found between the protocols for growth hormone and cortisol concentrations before the training sessions. However, in comparison with the value presented before the exercise sessions, all the protocols induced an acute elevation in the growth hormone concentrations, while no differences for cortisol were presented. Growth hormone concentrations were shown to be higher for 30 seconds intervals, when compared to the other rest intervals, however, the total work (total number of repetitions x load) was significantly lower for the session that used 30 seconds interval, compared with those sessions using 60 and 120 seconds. However, in the training for the strength development, longer rest intervals will be necessary to avoid significant declines in the number of repetitions, therefore the capacity to maintain the number with a constant intensity can result in greater muscular strength gains (Willardson, 2006; Willardson and Burkett, 2008). Our results are in accordance with this statement, suggesting that when training for muscular strength, resting five-minute might be advantageous to accumulate a higher training volume while also maintaining the intensity of the load lifted for upper- and lower-body. Additionally, it has been shown that training not to failure may be more advantageous for maximal strength gains than training to failure, so longer rest intervals (five-minute) would be necessary (Peterson et al., 2005). In other previously conducted experiments of the influence of distinct intervals between sets, the movement velocity of the exercises was controlled (Willardson and Burkett, 2005; 2006a; 2006b). In our experiment that was not possible, due to the fact that there was a constant decrease in cadence from the first to the last repetition to failure, and one of the indicators of the concentric failure utilized was the reduction in the movement velocity and the consequent pause at concentric phase. Nevertheless, the first repetitions were performed at high velocity and, when fatigue was established, there was a significant decline in velocity, until the exercise was finish. This may be a limiting methodological factor of our experiment, since it may affect the number of repetitions, fatigue and type of strength being trained. |