Introduction
Repetition tempo is a relatively new concept in resistance exercise that involves manipulating the timing of eccentric and concentric phases, along with rest intervals between the 2. Although repetition tempo has been studied at minimum, application of the concept is applicable to acute performance testing. In the National Football League (NFL) Scouting Combine, testing requires athletes to complete bench press repetitions to failure with a predetermined resistance of 225 lb. It is unknown if repetition tempos containing interrepetition rest enhance performance, but it is speculated that an increase in interrepetition rest may allow time for the removal of metabolic end products and phosphocreatine replenishment (2,6) to delay the onset of fatigue. Furthermore, introducing bottom rest (2) or altering the length of the eccentric phase (5,6,9) may also impact set performance. Lifting with a repetition tempo that promotes maximal repetitions would increase performance, not because the athlete is stronger, but because the repetition tempo allows for enhanced performance.
In a study where interrepetition rest was manipulated, power output (PO) of succeeding repetitions during a set was seen to significantly decrease when repetitions were performed without rest between repetitions (6). Lawton et al. (6) manipulated repetition tempo by allowing interrepetition rest of 23 seconds between each repetition, 56 seconds between every other repetition, or 118 seconds between every third repetition. All 3 conditions produced greater PO than the no-rest continuous lifting condition with no difference observed between interrepetition rest conditions. However, subjects reracked the bar during interrepetition rest intervals, and this is not common practice during acute performance testing.
For practical purposes, time-efficient resistance training does not involve prolonged interrepetition rest intervals (e.g., 23 seconds or more). Casual observation of weight lifters (unpublished data) revealed short interrepetition rest, rarely exceeding 3–5 seconds, and a typical set of 6–8 repetitions took approximately 12–16 seconds at a fast repetition tempo whereas a slower repetition tempo could take up to 1 minute. These tempos have practical application to acute performance testing, unlike sets of 3–4 minutes as seen in the study by Lawton et al. (6).
Altering repetition tempo to maximize performance (e.g., PO and repetitions completed) may benefit athletes during acute performance testing, but there are no studies of optimal repetition tempo during a set of resistance exercise. Therefore, the purpose of this study was to investigate how simultaneously varying eccentric velocity, bottom rest, and interrepetition rest (i.e., repetition tempo) would affect PO and the number of repetitions performed during a set of bench press. We hypothesized that performing with a fast eccentric phase, no bottom rest, and a short interrepetition rest would maximize PO and the number of repetitions.
Methods
Experimental Approach to the Problem
This study used a repeated measures design to determine the effects of repetition tempo on PO and number of bench press repetitions. One repetition maximum (1RM) testing established a submaximal workload for the 6 experimental trials. Each trial used a unique repetition tempo that included combinations of 2 eccentric speeds, 2 bottom rest intervals, and 2 interrepetition rest intervals. Table 1 explains the 6 tempo protocols used. The 6 trials were administered in a partially randomized and counterbalanced fashion. Power output (i.e., peak power output [PPO], average peak power [APP], maximum mean power [MMP], average mean power [AMP]) and number of repetitions were determined via video capture and compared using multiple 1-way repeated measures of analysis of variance (ANOVA).
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Table 1: Repetition tempos used during testing sessions.
Subjects
Twenty-four college-aged men (age 20.7 ± 1.7 years, height 176.3 ± 6.7 cm, weight 84.0 ± 14.1 kg, and 1RM 101.5 ± 19.9 kg) voluntarily participated in this study. Only those who participated in resistance training at least twice a week for at least the past 6 months and had no health or physical limitations for strength training were accepted as subjects. Participants were asked to maintain dietary habits throughout testing and refrain from any upper body training in the 24 hours preceding testing sessions. The study was approved by the Ithaca College Human Subjects Review Board, and informed written consent was obtained from all subjects before participation in the study.
Procedures
Subjects completed 1RM testing to determine an 80% 1RM load for use during the 6 tempo-testing trials. At the beginning of each session, subjects warmed up on a Monark cycle ergometer for 5 minutes with a resistance of 1 kp at a self-selected cadence. Within 1–2 minutes of completing the warm-up, subjects began 1RM bench press testing as described by Baechle and Earle (1). During all trials, subjects had their feet crossed and elevated above the bench to deter using their legs and prevent undesired accessory muscle movement. Additionally, a strap was placed around their waists to secure them to the bench and eliminate back arching variability across trials. Grip width was measured and maintained across all testing sessions. All testing sessions were separated by at least 48 hours to attenuate intersession performance effects.
On 6 separate occasions, subjects performed repetition tempo testing after the warm-up protocol, previously described. Subjects reported to the laboratory at the same time of the day during a 3-week period in March 2009. Subjects then became familiar with the cadence of the day (i.e., 1 of the 6 repetition tempos—see Table 1) with the assistance of a metronome while completing 3–4 repetitions with 50% 1RM. The subject was to focus on each of the 4 phases (eccentric, bottom rest, concentric, and interrepetition rest—see Table 1) of tempo while practicing repetitions. After the familiarization, subjects performed 1 set of bench press to failure with 80% 1RM to the assigned repetition tempo. Subjects were instructed to move the weight at the prescribed repetition tempo and continue performing repetitions until volitional fatigue. Volitional fatigue was defined as being physically unable to move the bar; improper form used to perform a repetition (use of accessory muscle movement of legs, back, or shoulders), or tempo could not be maintained in accordance with the metronome. Subjects maintained all phase durations within 0.59 seconds of the desired duration. Concentric phase velocity was maximized, averaging 1.55 ± 0.3 seconds across all tempo trials.
Data Collection and Processing
Peak Motus software (version 8.4.3, Peak Performance Technologies, Inc., Centennial, CO, USA) was used to capture normal speed (60 Hz) video of a retro reflective marker placed on the end of the bench press Olympic bar and automatically digitize movement of the bar. The camera (NEC T1-23A, Tokyo, Japan) was 0.87 m high and at a distance of 4.5 m from the close end of the bar, providing a 2-m × 3-m view of the sagittal plane of the bar trajectory and was connected to the Peak Motus computer via an analog to a digital converter. Raw 2D coordinates were scaled and filtered using Quintic Spline processing with the spline parameters automatically selected (Peak Motus) and then exported to a custom analysis program written in LabView (version 8.6.1, National Instruments, Austin, TX, USA) to determine power, work, and time-dependent variables.
Calculation of Power
Power was calculated using P = F × v, where velocity was determined from the first derivative of position data. Knowing the mass of the bar, horizontal force was obtained using Newton's second law of motion, F = m × a by taking the product of mass and horizontal acceleration. Acceleration was calculated as the second derivative of position data. Vertical force was calculated as the weight of the bar plus the product of mass and vertical acceleration. The resultant of the vertical and horizontal forces was the applied force on the bar, which was used in the calculation of power. The greatest concentric power and greatest average of concentric power values of any repetition in a set were defined as peak power output and maximum mean power, respectively. The average of these values for all repetitions in a set was defined as average peak power and average mean power, respectively.
Determination of Start and Stop of Each Phase
The beginning and the end of each phase were defined as the instances the vertical bar velocity rose above −0.05 m·s−1 or fell below 0.05 m·s−1, respectively. These instances were determined automatically using a computer algorithm that searched through the vertical velocity backward and forward from the midpoint of each repetition, finding the instant the bar velocity went above or below the threshold (Figure 1C). To minimize noise in the velocity data leading to false positives during this step, the position data were refiltered at a cut-off frequency of 1.5 Hz, tempos A–D, or 2 Hz, E–F, before calculating the velocity. This overfiltered position data were used only for the identification of the beginning and the end of each phase; it was not used in the calculation of power.
Figure 1: Raw, filtered, and derivative data of the bar. A) Raw positional data of the bar. B) Filtered data from (A). C) First derivative of (B). Used to calculate velocity in the power equation and find local starts and stops of each tempo phase. D) First derivative of (A). E) Filtered data from (D). Used to find local velocity minimums and maximums to determine midpoints of each repetition.
The midpoints of the eccentric and concentric phases of each repetition were identified from local vertical velocity minimums and maximums using thresholds of <−0.1 m·s−1, tempos A–D, or −0.12 m·s−1, tempos E–F, respectively, for minimums and >0.15 m·s−1 for maximums (Figure 1E). The velocity had to be greater than or less than the threshold for 45 data points to count as a local minimum or maximum, respectively. To minimize errors in determining the midpoint of each phase, the vertical velocity calculated from the original position data, was filtered using a low pass fourth order Butterworth filter with a cut-off of 0.5 Hz. This filtered vertical velocity was not used in the calculation of power.
The start and the end of each phase were determined on a graph of vertical position data (Figure 1A). Each trial was visually inspected and adjusted using an interactive graphing tool if the algorithm failed to find the correct phases. This occurred for approximately one-half of the trials. The process of the computer algorithm is depicted on exemplar data in Figure 1.
Statistical Analyses
One-way ANOVA with repeated measures compared differences between the 6 tempos for each variable (i.e., number of repetitions, PPO, APP, MMP, and AMP). Significant F values were further analyzed using Bonferroni adjustments. When assumed sphericity was violated, a Greenhouse–Geisser correction was implemented. All statistical analyses were performed on SPSS version 17.0 (SPSS, Inc., Chicago, IL, USA) with an alpha level set at 0.05.
Results
The ANOVA revealed a significant difference between tempos for the number of bench press repetitions completed. Repetitions for tempo A were 76.8, 68.7, 54.5, and 70.0% greater (F[1,23] = 494.73, p ≤ 0.000, η2 = 0.96) than the repetitions for tempos B, D, E, and F, respectively. Repetitions for tempo C were 88.0, 84.3, 68.9, and 85.8% were greater than (p ≤ 0.000) the repetitions for tempos B, D, E, and F, respectively. No significant differences were found between tempos A and C nor between tempos B, D, E, and F for any variable. Table 2 illustrates repetition and PO results for the 6 tempos. Figure 2 illustrates PPO across all repetitions performed with all tempos.
Table 2: Mean ± SD of repetitions and concentric power variables.
Figure 2: Peak power outputs of all repetitions for each repetition tempo.
The ANOVA revealed a significant difference between tempos for PPO and APP. The PPO values for tempo A were 19.8, 18.5, 18.5, and 26.4% greater than (F[1,23] = 711.73, p ≤ 0.000, η2 = 0.97) the PPO values for tempos B, D, E, and F, respectively. The PPO values for tempo C were 24.1, 22.8, 22.8, and 30.1% greater than (p ≤ 0.000) the PPO values for tempos B, D, E, and F, respectively. The APP values for tempo A were 21.2, 18.0, 20.4, and 26.5% greater than (F[1,23] = 541.69, p ≤ 0.000, η2 = 0.96) the APP values for tempos B, D, E, and F, respectively. The APP values for tempo C were 20.3, 17.2, 19.5, and 25.5% greater than (p ≤ 0.000) the APP values for tempos B, D, E, and F, respectively. No significant differences between tempos A and C nor between B, D, E, and F were found for PPO and APP.
The ANOVA also revealed a significant difference between tempos for MMP and AMP. The MMP values for tempo A were 26.8, 22.7, 21.2, and 30.8% greater than (F[1,23] = 743.01, p ≤ 0.000, η2 = 0.97) the MMP values for tempos B, D, E, and F, respectively. The MMP values for tempo C were 29.8, 25.6, 24.1, and 33.8% greater than (p ≤ 0.000) the MMP values for tempos B, D, E, and F, respectively. The AMP values for tempo A were 22.9, 18.5, 20.7, and 25.1% greater than (F[1,23] = 681.88, p ≤ 0.000, η2 = 0.97) the AMP values for tempos B, D, E, and F, respectively. The AMP values for tempo C were 21.6, 17.3, 19.5, and 23.9% greater than (p ≤ 0.000) the AMP values for tempos B, D, E, and F, respectively. No significant differences between tempos A and C nor between B, D, E, and F were found for MMP and AMP.
Discussion
The purpose of this study was to determine the most effective bench press repetition tempo to create the greatest PO and number of repetitions in a set. Lifting with short eccentric phases and no bottom rest (tempos A and C) produced greater repetitions and PO, and therefore, total work volume than repetition tempos with 4-second eccentric phases (tempos E and F) or 3-second bottom rest intervals (tempos B and D). Not only was greater PO produced in a single repetition, but it was also better maintained throughout the set. Normalization of power data with body mass did not produce significant changes in these results.
Previous research, supporting the present results, indicated that fast eccentric phases increase the number of successful repetitions by using the stretch-shortening cycle (SSC) (3,5,9). Augmented concentric contraction is often attributed to the storage and reuse of elastic energy from the series elastic component of the musculo-tendinous system (3). This increase in the rate of concentric contraction is observed especially in the initial phase of the contraction, when peak power is produced (3). Hatfield et al. (5) also found that faster eccentric speeds of a self-selected pace produced greater repetitions as compared to a 10-second eccentric phase. Sakamoto and Sinclair (9) studied varying speeds and concluded that 1 second and maximal speed eccentric phases resulted in higher repetitions than eccentric speeds of 2.8 and 1.4 seconds.
In this study, tempos containing 3 seconds of interrepetition rest produced similar repetitions and PO as their continuous lifting counterparts; this opposes the originally stated hypothesis. A study using much greater rest (23–118 seconds) with reracking the weight between repetitions demonstrated the potential for interrepetition rest to increase PO (6). Using a 3-second rest interval without racking the weight in the present study could not duplicate the benefit of interrepetition rest. A 3-second rest is more practical, but this short pause was not found to improve performance. Either the interrepetition rest needs to be longer or holding the weights with arms extended canceled any potential benefit of the short rest.
Repetition tempos with longer eccentric phases (i.e., tempos E and F) yielded lower PO than trials with shorter eccentric phases. This may be because of a fatiguing effect of greater eccentric time under tension (TUT), which refers to the total time a muscle performs work (5). Greater eccentric TUT (i.e., tempos E and F) may cause fatigue and thereby lessen repetition number compared to a set with lesser eccentric TUT (i.e., tempos A and C). Eccentric TUT may be important to positive long-term resistance training adaptations such as strength (8,11,12), power (7), and muscle fiber cross-sectional area (4,10,11). However, this study did not examine chronic training effects; therefore, the most effective training repetition tempo for enhancing resistance exercise adaptation is still unknown. Training with eccentric contractions preceding concentric contractions uses the SSC and increases PO as well (3), possibly leading to chronic performance gains. The impact of varying repetition tempo on PO, peak eccentric power, and eccentric TUT, and subsequently muscular adaptation is worthy of future study.
Interrepetition rest when used in multiple sets may improve PO over the course of a training session. Therefore, resistance training with interrepetition rest may chronically increase strength and power more than continuous lifting. Future training studies should address repetition tempos with varying interrepetition rest intervals (e.g., 3–5 seconds) for multiple sets. The present results relate primarily to acute performance in one set of resistance exercise. When a performance goal is high, total power from a single set of resistance exercise (e.g., during performance testing), repetitions with fast eccentric speeds, and no bottom rest are highly recommended.
Practical Applications
An increase in the number of repetitions is important for many strength tests in professional sports such as the bench-press test performed during the NFL Scouting Combine. The Combine requires athletes to lift a predetermined weight (225 lb) until failure and measures successful repetitions to compare athletes who play in similar positions. As seen in this study, lifting with a rapid eccentric phase and no bottom rest will result in a greater number of repetitions and the most successful outcome. Providing short interrepetition rest (1–4 seconds) while holding weight with arms extended during a bench press does not aid acute performance in a single set. Performance during other tests such as the Young Men's Christian Association bench press test and tests of muscular endurance (e.g., sit-ups and push-ups) should also predictably benefit from a repetition tempo with fast eccentric contraction and no bottom rest.
Acknowledgments
The authors wish to thank the subjects for their participation and Kevin Carriero who supplied the bench press equipment.
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