Strength training is effective in enhancing muscular strength, power, hypertrophy, and localized muscular endurance. These specific characteristics can be emphasized through the manipulation of prescriptive training variables, such as the load, volume, and rest interval between sets. A recent review, de Salles et al. (5) suggested that the independent manipulation of the rest interval between sets can elicit different acute responses and longitudinal adaptations in the neuromuscular and endocrine systems.
Several prior studies demonstrated that longer rest intervals between sets resulted in significantly greater repetitions vs. shorter rest intervals (9,11,12,14,17,18). Therefore, sufficient rest duration between sets might be an important variable for maximal strength improvement due to greater consistency in the repetitions per set with an absolute load, which may enhance the adaptational stimulus (14).
According to the American College of Sports Medicine (1), a program emphasizing maximal strength development should include variations with heavy resistance loads ranging from 1RM (1 repetition maximum) to 6RM for advanced individuals and athletes. However, the majority of studies that manipulated the rest interval between sets, utilized loads in the 8RM to 15RM range (9,11,12,14,17,18). Few studies in the literature have compared different rest intervals between sets with higher intensity loading schemes designed for maximal strength development. Weir et al. (16) and Matuszak et al. (7) analyzed the influence of different rest interval lengths on the capacity to successfully perform 2 consecutive 1RM sets for the bench press and back squat exercises, respectively.
Furthermore, Ratamess et al. (10) analyzed repetition performance and metabolic responses to 30 seconds, 1, 2, 3, or 5 minutes rest between 5 consecutive sets of the bench press with 5RM and 10RM loads. The authors observed similar patterns in repetition performance for the 5RM and 10RM sets and concluded that longer rest intervals promoted a greater volume of training vs. shorter rest intervals. However, this study (10) also focused on metabolic responses (e.g., oxygen consumption, heart rate, and blood lactate); for that purpose, the authors progressively reduced the relative load utilized per set in an attempt to maintain repetition performance. This approach did not allow for the direct assessment of repetition performance with an absolute load under different rest interval conditions.
Recently, the rating of perceived exertion (RPE) has been used for assessing the relative intensity of resistance exercise sets (6). Previous authors (13,14) reported that the RPE increased over the course of consecutive sets for a 1-minute rest interval condition vs. 3 or 5 minutes rest interval conditions when utilizing a 10RM load. Presently, no study has investigated repetition performance with different rest interval lengths when utilizing an absolute 3RM load over consecutive sets and with inclusion of RPE analysis. Therefore, the purpose of the current study was to compare different rest interval lengths between sets on repetition consistency and RPE during consecutive bench press sets with an absolute 3RM load in resistance trained men. We hypothesized that repetition performance would decrease and RPE would increase with shorter rest intervals between sets.
Experimental Approach to the Problem
After proper familiarization with experimental procedures, the 3RM for free weight BP were assessed on test and retest visits. After the load testing, subjects were randomly assigned in 4 different training sessions, one for each rest period tested (1, 2, 3 and 5-minute), with 48 hours between sessions. Experimental sessions were designed with 5 sets of 3RM loads in order to achieve repetition performance for each rest period and RPE values throughout the consecutive sets.
Sixteen trained men (23.75 ± 4.21 years; 74.63 ± 5.36 kg; 175 ± 4.64 cm; bench press relative strength: 1.44 ± 0.19 kg/kg body mass) volunteered to participate in this study. All subjects had a minimum of 1-year resistance training experience and had utilized the bench press in their routines. All individuals were delimited with the following inclusion criteria: (a) had performed resistance training for at least 1 year with a minimum frequency of 3 sessions per week; (b) could perform the bench press exercise with at least 125% of their body mass; (c) did not perform any other physical activity for the duration of the study; (d) did not present any medical conditions that could confound experimental procedures; and (e) stated they had not used anabolic-androgenic steroids or other ergogenic substances that may enhance repetition performance. Before data collection, all subjects answered ‘‘no’’ to all questions on the PAR-Q (15). All subjects were informed of the testing procedures and signed an informed consent in accordance with the Declaration of Helsinki. The experimental procedures were approved by the Ethics Committee of Federal University of Rio de Janeiro.
Determination of 3 Repetition Maximum
After 2 familiarization sessions, subjects attended 2 additional 3RM barbell bench press testing sessions. To minimize measurement error, the following strategies were adopted: (a) standard instructions concerning the experimental procedures were given to the subjects before the test; (b) subjects received standardized instructions on exercise technique (2); (c) body position was held constant; (d) verbal encouragement was provided during the bench press sets to elicit the maximum effort from each subject (8); and (e) the mass of all plates and bars used was determined using a precision scale. The initial loads for 3RM testing were estimated from loads utilized by each subject during the course of their daily periodized strength training routines. From this point, the load modification pattern followed a 2 kg (total minimal modification) manipulation for each attempt, and it was held consistent for each subject. The last successful lift was recorded as the 3RM; the greatest load lifted over the 2 testing sessions was considered the 3RM load. Each testing session was separated by 48 hours, and subjects were restricted from performing any structured exercise. Subjects performed a maximum of 5 attempts with a least 5 minutes rest between attempts.
Forty-eight to 72 hours after the last 3RM test, subjects were randomly assigned using a counter-balanced procedure to perform 5 sets of the bench press exercise with the 3RM load and with 1, 2, 3, or 5 minutes rest intervals between sets for a total of 4 experimental sessions. During all of the sessions, subjects performed 2 warm-up sets of 12 repetitions with 40% of a self-estimated 8RM load (9). A 2-minute rest period ensued after the warm-up sets before subjects began each rest interval protocol (9). No attempt was made to control the repetition velocity; however, subjects were required to use a smooth and controlled motion. The range of motion was standardized following the protocol of Weir et al. (16). All visits were conducted at the same time of the day. The total number of repetitions completed for each rest interval protocol was recorded at the end of the session. The Omni-Res RPE (6) was recorded before and after each set.
The alpha value of significance was p = 0.05. The Shapiro-Wilk normality and homoscedasticity tests (Bartlett criterion) were used to determine the sample distribution (3). All variables of sample characteristics presented normal distribution and homoscedasticity. A series of 1-way analysis of variances were conducted to assess differences in the total number of repetitions completed during each session and the number of repetitions completed for each set of each rest interval protocol. In the case of significant main effects, further comparisons were made via Bonferroni post hoc. The Friedman test was used to analyze the data originated from nonparametric scales (i.e., OMNI-RES) to compare differences in the RPE before and after each set within and between rest interval protocols. If necessary, a Dunn post hoc test was applied for multiple comparisons.
Additionally, to determine the magnitude of the findings, effect sizes (ES; the difference between the pretest score and the posttest score divided by the pretest standard deviation) were calculated for each set of each rest condition, and the thresholds proposed by Cohen (4) were applied to determine the magnitude of treatment effects. The Prism software (GraphPad, 6.0) was used for all statistical analyses.
Excellent test-retest reliability for bench press was demonstrated via the intraclass correlation coefficient (r = 0.99). In addition, a paired student’s t-test indicated no significant differences in the test-retest 3RM loads. Significantly, greater total bench press repetitions were completed with 2 (14.50 ± 1.79 repetitions), 3 (14.94 ± 1.18 repetitions), or 5 (14.75 ± 1.00 repetitions) minutes vs. 1 (12.50 ± 2.68 repetitions) minute rest between sets (p ≤ 0.05); no significant difference was noted between the 2, 3, and 5 minute rest conditions (Table 1). For the 1-minute rest condition, a significant reduction in repetitions (relative to the first set) was noted commencing with the second set; whereas, for the other rest conditions (2, 3, and 5 minutes), a significant reduction in repetitions was only noted for the fifth set (Table 1; Figure 1).
The ESs were calculated using the repetition number of the first set as the pretest score, the repetition numbers of the second through fifth sets as the posttest scores, and the SD of the first set as the pretest standard deviation. The ES data demonstrated large magnitudes of repetition reductions for the 1-minute rest condition commencing with the second set. For 2, 3, and 5 minutes rest conditions; the large ES pattern was evident commencing with the third and fourth sets (Table 2).
Significant increases in RPE “before each set” were evident over successive sets, with significantly greater values for the 1-minute rest condition. The RPE values were significantly greater commencing with the second set for the 1 vs. 3 and 5 minutes rest conditions. Significant increases in RPE were also evident after each set between the 1 and 5 minutes rest conditions commencing with the second set and continuing over successive sets (Table 3).
The key finding from the current study was that when utilizing an absolute 3RM load, a shorter rest interval (i.e., 1 minute) resulted in significantly greater reductions in repetition performance and increments on perceived exertion over 5 consecutive sets vs. the longer rest interval conditions (i.e., 2, 3, and 5 minutes). Additionally, higher RPE scores before initiation of each set were observed with 1 and 2 minutes rest intervals between sets. The RPE after completion of each set was lower with longer rest intervals between sets. To our knowledge, this was the first study that directly investigated the acute responses of different rest interval lengths when utilizing an absolute 3RM load over subsequent sets. Through the analysis of the results, it became evident that a minimum of 2 minutes rest between sets was necessary for consistency in repetition performance for 4 of 5 sets with an absolute 3RM load. However, 3 minutes rest between sets was necessary for consistent repetition performance over all 5 sets. Therefore, resting 5 minutes between sets is not necessary and would exceed the recovery requirement when utilizing an absolute 3RM load.
According to the American College of Sports Medicine (1), the loading recommendation for optimizing muscular strength in advanced lifters is in the 1RM to 6RM range. Previous studies had compared different rest interval lengths on the capacity to perform 2 consecutive 1RM sets (8,16). Specifically Weir et al. (16) demonstrated that for the bench press, subjects were able to successfully perform consecutive maximal attempts with only a 1-minute rest interval in-between; and there were no performance differences noted when resting 1, 2, 3, 5, or 10 minutes between consecutive maximal attempts.
Consistent with these findings, Matuszak et al. (8) reported no statistical difference in the capacity to perform consecutive maximal back squat attempts for 1, 3, and 5 minutes rest conditions. Although, our study differs from these studies by performing 5 consecutive sets with a slightly lighter load (i.e., 3RM); our results demonstrated that the 1-minute rest protocol resulted in significant reductions in the consistency of repetition performance commencing with the second set.
Several authors have assessed repetition performance with lesser loads ranging from 8RM to 15RM. For example, Willardson and Burkett (18) compared the effects of 3 different rest intervals on bench press and back squat repetitions. Four sets of the bench press and back squat were performed with an 8RM load and 1, 2, or 5 minutes rest intervals between sets. The authors demonstrated that for the back squat exercise, significantly greater total repetitions were completed for the 5-minute rest condition vs. the 1 and 2 minutes rest condition with no significant difference between these conditions. However, for the bench press exercise, they found differences between each condition, and as the length of the rest interval increased, significantly greater total repetitions were completed. These results were not consistent with the current study for the 3RM loads, in which there was no significant difference in repetitions performance between the 2 and 5 minutes rest conditions. We speculate that the major reason for this outcome is the greater time under tension and accumulating metabolic acidosis that would be associated with consecutive sets at an 8RM load vs. a 3RM load.
Other recent studies demonstrated declines in repetition performance in successive set for the lower and upper body (14). Senna et al. (14) compared repetition performance and RPE with 1, 3, and 5 minutes rest intervals between sets of multi- and single-joint resistance exercises. Fifteen resistance trained men, completed 12 sessions (4 exercises and 3 rest intervals), with each session involving 5 sets with 10RM loads for the bench press, machine leg press, machine chest fly, and machine leg extension exercises with 1, 3, and 5 minutes rest intervals between sets. The results indicated significantly greater bench press repetitions with 3 or 5 minutes rest vs. 1-minute rest between sets with no significant difference evident between the 3 and 5 minutes rest conditions. For the other exercises (i.e., machine leg press, machine chest fly, and machine leg extension), significant differences were evident between all rest conditions (1, 3, and 5 minutes). For all exercises, consistent declines in repetition performance (relative to the first set) were observed for all rest conditions, starting with the second set for the 1-minute condition and the third set for the 3 and 5 minutes rest conditions. Furthermore, significant increases in RPE were evident over successive sets for both the multi- and single-joint exercises, with significantly greater values for the 1-minute rest condition.
In the current study, a significant decline in bench press repetitions was evident only for the 1-minute rest condition. However, for the other 2, 3, and 5 minutes rest conditions, there were no significant differences in repetition performance. As for the RPE, our results indicated significantly higher scores before initiating sets for the 1 and 2 minutes rest conditions. The RPE after completion of each set was also significantly higher for the 1-minute vs. the 5-minute rest condition.
The current study adds to the growing body of knowledge concerning the importance of prescribing a structured rest interval between sets. Our results suggest that the rest interval between sets directly affects the repetitions completed over successive sets and the RPE with an absolute 3RM load. Our findings can be applied by trainers and coaches to optimize resistance training programs which have both muscular strength and muscle hypertrophy as primary and secondary goals, respectively. Our data indicate that a minimum of 2 minutes rest between sets was necessary for consistency in repetition performance for 4 of 5 sets with an absolute 3RM load. However, 3 minutes rest between sets was necessary for consistent repetition performance over all 5 sets. Therefore, resting 5 minutes between sets is not necessary and would exceed the recovery requirement when utilizing an absolute 3RM load. Thus, it is important to highlight that these results are specific to the exercise, rest interval, load, and population examined.
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