Strength and conditioning professionals frequently manipulate a selection of variables when designing resistance training programs. Some of the more commonly used program design variables are exercise intensity, volume, duration, rest period, and exercise selection (5,15). Changes are made to programs to prevent overtraining, reaching a plateau, and boredom. The effects of many of these manipulations on strength development have been extensively studied (5,9). One variable that has not received a great deal of study is that of lifting tempo (also known as pace or cadence). In this study, the term tempo refers to the speed with which exercise is performed as individuals attempt to keep pace with a metronome; it is therefore an intentional action (15). Commonly, tempo selection is volitional in most research studies, yet practitioners frequently select tempos for their clientele with 2/0/2 and 2/0/4 being two of the more common ones. Several lay publications suggest that lifting tempo is of great importance for the optimal development of strength (11,13,21,24).
By controlling the lifting tempo, one is able to modify the effect of momentum (21). Two types of slow-velocity contractions have been identified in the literature: unintentional slow-velocity contractions and intentional slow-velocity contractions (15). The former occurs when an individual is forced to reduce the velocity of a repetition attempt because of fatigue. Intentional slow-velocity contractions occur when a deliberate attempt is made to control the speed with which a movement occurs. Intentional slow-velocity training has been shown to lead to a reduction in force production and neural activity (15). This type of training has been advocated for use among individuals who are beginning a resistance training program (15).
In recent years, the superslow tempo (10/0/5 or 10/0/10) has been used with the relatively untrained and trained lifters (10,11,24). The superslow tempo has been linked to feelings of discomfort and greater levels of perceived exertion (ratings of perceived exertion, RPE). To the authors' knowledge, there are no published data examining the impact of resistance exercise performed at different tempos on the release of key hormones that are known to influence cellular signaling events and ultimately muscle development. It has been previously noted that lower loads are used to complete intentionally slow-velocity contractions. Some have noted that because of these lower loads, the muscles are exposed to a less than optimal stimulus for strength development (13-15). Furthermore, the use of intentionally slow-velocity training has been recommended for use in the beginning stages of a resistance training program with inexperienced individuals. However, few data exist that examine the impact of differences in the moderate, not slow, intentional velocity range on both force production/maximal strength and the hormonal responses to exercise performed at moderate-velocity ranges. Therefore, the study was divided into 2 parts: part 1 was designed to determine the maximal load that could be lifted by experienced lifters using a standard tempo compared with a slower tempo. Both velocities selected were within the moderate range (15) and were selected because they are commonly used in resistance training programs. Additionally, this information was used as a basis of determining appropriate loads for part 2 of the study, which was designed to compare the metabolic and hormonal responses of experienced lifters bench pressing at the 2 previously used tempos while working at the same relative intensity. The bench press was chosen in this study, although it uses a small amount of muscle mass, because it is a very commonly used exercise by resistance trained individuals, and the loads used can be very easily controlled and therefore subject safety was enhanced (14). Furthermore, the bench press has been frequently studied; however, there are no data on the impact of tempos on the metabolic responses of individuals. Because less weight has been reportedly used during slower velocity contractions, some believe that there is less likelihood of favorable strength changes occurring with a program designed with this type of training. To mediate these changes, there would of necessity be perturbations of key anabolic hormones that regulate muscle growth and development. It was therefore hypothesized that the metabolic and hormonal responses would be greater in a sample of experienced resistance-trained individuals when exercise was performed with the faster 2/0/2 tempo compared with the slower 2/0/4 tempo.
Experimental Approach to the Problem
Lifting tempos are commonly expressed in seconds with the first number representing the concentric phase, the middle number the transition period between concentric and eccentric, and the third number the eccentric phase of the exercise. Initially, maximal strength during bench pressing was determined in 17 male subjects on 2 separate occasions using 2 different lifting tempos, 2/0/2 and 2/0/4. These 2 tempos were chosen because they are commonly used in the majority of resistance training programs and fall within the moderate-velocity range (15). As a follow-up to the first study, 12 male resistance-trained subjects were used to examine the metabolic and hormonal responses to bench pressing at the aforementioned tempos at the same relative intensity (Figure 1). We hypothesized that the metabolic and hormonal responses to the 2 tempos would be greater for the 2/0/2 than for the 2/0/4 tempo. We made our subjects perform the exercise task at the same relative intensity to make valid comparisons between the 2 tempos. The blood parameters selected (i.e., lactate, testosterone, human growth hormone, insulin like growth factor-1 [IGF-1], cortisol, and creatine kinase) were chosen because they either indicate muscle metabolic activity or they have impact upon muscle growth and development.
Seventeen healthy men with age ranging from 22 to 28 years served as subjects. All had been weight training for at least 2 years and regularly included the bench press exercise as part of their training program. Subjects were informed of the experimental risks and signed an informed consent document before the investigation. The investigation was approved by the Institutional Review Board for the use of human subjects of Springfield College. Subjects also completed a Medical History and Physical Activity History questionnaire. No one with a prior shoulder injury, as self-reported, was permitted to participate.
Subjects were administered 2 maximal strength (1 repetition maximum [1RM]) bench press tests at least 5 days apart with both tests being conducted at the same time of day. Tests were administered randomly in a counterbalanced order. One week before testing, subjects were asked to avoid any exercises that targeted the chest and/or triceps. Exercises targeting the shoulder musculature were avoided for 48 hours before testing. Any form of resistance training was prohibited for the 24 hours before testing. It was requested that subjects eat their last solid meal no later than 2 hours before the scheduled test time. Fluid consumption was permitted with the request that the same pattern be repeated for both testing sessions. Only 2 of the subjects reported taking protein supplementation in their diets; therefore, they were instructed to continue doing so for the duration of the study. Body weight, height, and body composition were recorded. Body composition was assessed using skinfolds with standard equations used to estimate body density and body fat (12,22).
Subjects provided a self-reported 1RM value, which was used by the investigators for determination of the appropriate exercise intensity. Before all testing sessions, the same 10-minute whole-body dynamic flexibility warm-up was used. During the first session, the 1RM of each subject was determined using the protocol as described in Table 1. Subjects performed these 1RM tests using either the 2/0/2 or 2/0/4 tempos. Subjects were required to adhere to the specified tempo, and the 1RM was the maximum weight that they could lift at the specific tempo for that day. Maximal testing has been performed routinely at Springfield College as part of the strength and conditioning program, and the testing in this study was performed by the same group of researchers who followed a standardized protocol.
For safety purposes, 3 spotters were present, one at each end of the bar and one at the center of the bar. A metronome was used to assist subjects in maintaining the proper lifting tempo. Subjects practiced the specific tempo for the day, before performing the required exercise. Subjects achieved their 1RMs within 3-5 attempts after the preliminary warm-up sets.
Heart rate was assessed using a polar heart rate monitor (Polar, Lake Success, NY, USA). Ratings of perceived exertion, for the whole body, and the chest musculature were collected at each workload (20). Both heart rate and RPE were recorded immediately after each 1RM test.
Twelve men between the ages of 22 and 39 years with at least 2 years of weight training experience were recruited for this study (Table 2). These subjects were different from the 17 who completed part 1 of the study. Subjects followed similar instructions as in part 1; however, for sessions 3 and 4, subjects were asked to come to the laboratory in the morning after a 12-hour fast because food ingestion is known to impact metabolic and hormonal variables (17,18). The research sessions were separated by at least 5 days. Subjects came to the laboratory at the same time of day, typically in the morning between 8 am to 12 pm for each of their testing sessions.
Preliminary Testing Sessions
Maximal strength was determined using the same protocols as described in Table 1 from part 1 of the study. These values were used to compute the exercise intensities for sessions 3 and 4.
Experimental Sessions 3 and 4
After completing the 1RM testing sessions, subjects returned to the laboratory for their third and fourth research sessions in which metabolic and hormonal responses were studied. Subjects followed instructions as previously described. Subjects sat for 10 minutes after which a baseline heart rate and a venous blood sample were taken. Additionally, capillary puncture was performed and samples were analyzed for hemoglobin (Reflotron, Boehringer Mannheim, Indianapolis, IN, USA) and hematocrit. Subjects were required to perform 4 sets of the bench press exercise with 1-minute rest periods between sets. During the first set, they completed 4 repetitions at 55% of their 1RM; in the second set, they did 5 repetitions at 60% of their 1RM; in the third set, they did 6 repetitions at 65% of their 1RM; and in the final set, they attempted to complete as many repetitions as possible using a weight that represented 75% of their 1RM at the specified tempo. The 2 experimental sessions (i.e., sessions 3 and 4) were performed at the same time of day for each subject, in the morning between 8 am and 12 pm, and the order of these testing sessions was counterbalanced.
The distance that the bar traveled from its lowest point on the chest until the arms were fully extended was measured and used to compute the amount of work performed by the subjects during each set under the 2 tempos. The work performed during each set was computed using the following equation (3):
The total work performed during the exercise session was determined by adding the work completed during each of the 4 sets. The power generated (watts) during the fourth set was computed by dividing the work performed during that set by the time needed to perform that work (3).
The serum from each subject was analyzed for lactate, testosterone, human growth hormone, IGF-1, cortisol, and creatine kinase. Immediately after the final set (with the subject in a seated posture as at baseline) and within approximately a 30- to 60-second period, another venous blood sample was taken and processed in the same way as the baseline sample. Furthermore, a capillary sample was taken and analyzed for hemoglobin and hematocrit as at baseline before exercise. These hematocrit and hemoglobin values were used to correct the post-exercise blood parameters for changes in plasma volume (PV) (8). Cortisol and testosterone were analyzed using enzyme-linked immunoassay (10-2,000 and 10-4,000; Diagnostic Systems Laboratories, Webster, TX, USA), which have a sensitivity of 3 nmol·L−1 and 0.1 nmol·L−1, respectively. IGF-1 and GH were analyzed using enzyme-linked immunosorbent assay (10-5,600 and 10-1,900; Diagnostic Systems Laboratories), which have a sensitivity of 0.004 nmol·L−1 and 0.03 μg·L−1, respectively. Creatine kinase was analyzed using a kinetic assay (310-40; Diagnostic Chemicals Ltd., Charlottetown, Canada) measured by a spectrophotometer (Biomate 3; Thermo Spectronic, Rochester, NY, USA). Lactate was measured using an automated lactate/glucose analyzer (Stat 2300 Plus; YSI, Yellow Springs, OH, USA), which has a precision of ±2%. All samples were analyzed in duplicate in the same assay run for a particular variable to avoid interassay variances. The intra-assay variance was less than 5% for all assays.
Repeated-measures T-tests were used to compare the 1RMs, total work, power output, repetitions completed, PV change, RPEs, and heart rates between the 2 tempos. A 2 (tempo) × 2 (time) repeated-measures analysis of variance was used in part 2 to compare the effect of the 2 tempos on metabolic and hormonal variables. Following a significant interaction, a simple effects test was performed. All statistical analyses were performed using the Statistical Package for Social Sciences 15.0.1 for Windows (SPSS, Inc., Chicago, IL, USA). Significance was determined at p ≤ 0.05.
All data are presented as means ± SEM. Seventeen subjects completed part 1 of this study, whereas a total of 12 different subjects completed part 2 of the study. Their physical characteristics are recorded in Table 2. In part 1 of the study, 1RMs (lbs) of the subjects were 3.7% higher on the 2/0/2 tempo (242.1 ± 11.3) than on the 2/0/4 tempo (234.4 ± 10.8) (p < 0.001). Both whole-body (WB) and local chest (C) RPEs (Borg 0-10 scale) were statistically higher on the 2/0/4 (WB: 4.9 ± 0.6, C: 6.6 ± 0.6) than on the 2/0/2 tempo (WB: 4.1 ± 0.6, C: 5.7 ± 0.6), (p < 0.05). The heart rate (b·min−1) did not differ between the 2 tempos (2/0/2: 128.6 ± 3.8; 4-0-2: 128.2 ± 4.3) (p > 0.05) (Table 3).
In part 2 of the study, the mean 1RM (lbs) for the 2/0/2 tempo (247.5 ± 12.9) was 3.9% higher than when the subjects performed the 2/0/4 tempo (237.9 ± 12.5) (p < 0.05). The total work (joules) performed by the subjects during the 4 sets was significantly greater (10.8%) when the subjects used the 2/0/2 tempo (5,987.8 ± 297.9) compared with when they used the slower tempo (5,339.5 ± 259.7) (p < 0.05). The amount of work (joules) performed during the fourth set, when the subjects attempted to perform as many repetitions as they could using 75% of their measured 1RM, was greater when the subjects used the 2/0/2 tempo (2,044.5 ± 175.4) than when they used the (2/0/4) tempo (1,459.9 ± 115.6) (p < 0.05). Furthermore, the power (watts) generated during the fourth set was greater while subjects used the 2/0/2 tempo (81.2 ± 4.2) compared with when they used the 2/0/4 tempo (53.3 ± 2.9) (p < 0.05). Subjects were able to complete more repetitions at a weight that approximated to 75% of their 1RM when they used the 2/0/2 tempo (6.4 ± 0.6) than when they used the 2/0/4 tempo (4.7 ± 0.4) (p < 0.05) (Table 4). The heart rates (b·min−1) recorded at the completion of the fourth set were almost identical between the 2 tempos, whereas the RPEs were not different (p > 0.05).
The change in PV (% change) was significantly different between the 2/0/2 tempo (0.96 ± 1.2) and the 2/0/4 tempo (−5.7 ± 1.7), p < 0.05 (Figure 2). This finding had a substantial impact upon the blood parameters measured. Without the correction for PV change, there was no significant time-by-tempo interaction nor main effect for tempo for any of the measured blood parameters (i.e., lactate, testosterone, human growth hormone, IGF-1, cortisol, and creatine kinase). But, there was a significant time effect, with concentrations of each of these parameters being significantly (p < 0.05) higher immediately after the fourth set compared with baseline before exercise. However, when the data were corrected for changes in PV, there was a significant time-by-tempo interaction for IGF-1 (effect size = 0.39) with levels increasing significantly after the exercise bout using the 2/0/2 tempo (pre-exercise: 277.4 ± 21.8; post-exercise: 308.1 ± 22.9, ng·mL−1), but remaining the same following the 2/0/4 tempo (pre-exercise, 277.2 ± 17.6; post-exercise 284.8 ± 21.2, ng·mL−1) (p < 0.05) (Figure 3). Furthermore, the significant main effect for time that was seen for creatine kinase and testosterone (when not corrected for changes in PV) was no longer present.
The current study was designed to determine the effect of performing the bench press using 2 tempos that are classified as being in the moderate-velocity range ([2/0/2] compared with a [2/0/4] tempo) on the metabolic and hormonal responses of experienced lifters. We had hypothesized that the metabolic and hormonal responses would be greater after the 2/0/2 tempo. We found that the subjects in this study were able to lift more weight (i.e., had a higher1RM) and were able to perform more total work with the 2/0/2 tempo during 4 sets of exercise than with the 2/0/4 tempo. Generally, the metabolic and hormonal responses measured were similar between the 2 tempos under investigation with the exception of IGF-1, which was found to increase significantly with the 2/0/2 tempo but to remain essentially the same after the 2/0/4 tempo.
One of the most interesting findings of the study was the fact that the 2/0/4 tempo caused a significant reduction in PV compared with the faster 2/0/2 tempo, and this difference had an impact on the way in which the hormonal data were interpreted. As has been previously established in dynamic aerobic exercise, acute resistance training exercise leads to a reduction in PV and subsequent hemoconcentration (1,2,6,7). The magnitude of this reduction is related to the exercise selection and relative intensity of the resistance exercise performed (6,7). Recently, a research group noted that a number of confounding variables have not been accounted for in previous studies examining the impact of exercise training on PV. One major variable is posture, and they found that posture accounted for 40-47% of the change in PV recorded after 2 (10RM vs. 5RM) different resistance training exercise protocols (7). The effect of lifting tempo on PV change has not been reported. The 5.7% PV reduction noted with the 2/0/2 tempo in the present study was less than the 7-14% reduction previously reported by others; however, a lower volume (sets × repetitions) of exercise was used (1,2,6). Our results are similar to the findings reported by Craig et al. (7) because they found greater PV reduction in the protocol in which the time under tension was greater (10RM vs. 5RM).
Our findings underline the importance of correcting for PV changes in research in which blood parameters are measured either during or immediately after exercise because there were no differences in the metabolic or hormonal data without correcting for the observed changes in PV. However, when the data were corrected for the change in PV that occurred because of the exercise bout, the interpretation of the results was different. Hemoconcentration occurred as a result of the 2/0/4 tempo. Hence, without taking this into account, the increase in the measured blood parameters appeared to be greater as a result of the exercise bout than was actually the case. It can be argued that the uncorrected measured values are the actual molar concentrations of the metabolites to which the receptors in the tissues are exposed. Despite this fact, it would seem prudent to suggest that researchers who are looking for the true impact of the exercise intervention on the hormones and metabolites measured in a study like this may wish to take PV changes into account.
In both parts 1 and 2, it was determined that individuals can lift more weight using the 2/0/2 tempo than using the slower 2/0/4 tempo. Others have similarly reported that slower velocity contractions result in lower maximal loads (14). In part 1, the difference was approximately 3%, whereas in part 2, the difference was 4%. These small differences were statistically different between the tempos. The reason for the difference is unclear, but some claim that using faster tempos introduces the element of momentum into the exercise, making rapid acceleration possible at the beginning and end of the movement (21,24). Power output was also higher with the faster tempo. Our findings are consistent with those reported by Hatfield et al. (10) who also found individuals can perform more work when a faster tempo is used. The tempo used in the Hatfield et al. (10) study was slower (10-second concentric and 10-second eccentric) than what we used, but the conclusions with regard to performance indices were similar.
If training with a slower tempo is to be superior with regard to muscle strength and size development, as some claim, then training under such conditions should lead to metabolic and hormonal responses to mediate these changes. It is well known that initial increments in strength are caused by neurological changes, most of which are attributed to the eccentric phase of the movement (23). Beyond this initial phase, further increments are caused by changes in the contractile tissue (13). These changes in contractile tissue are influenced by the hormonal milieu generated by the resistance training program (16). The key anabolic hormones are testosterone (particularly in men), growth hormone, and the IGF-1 system. These hormones influence the changes that occur after a resistance training program via an interaction with specific androgen receptors (19). The hormone cortisol is also thought to play a key role in the remodeling process that accompanies a well-designed resistance training program (16,19).
In part 2, an effort was made to equate the relative intensity of the exercise performed at the 2 selected tempos by having our subjects work at 75% of their measured 1RM. As expected, we found that the bout of exercise performed led to an increase, over time, in each of the metabolic variables assessed. Surprisingly, we found that there was an increase over time in the IGF-1 levels when the 2/0/2 tempo was used and not when the 2/0/4 tempo was used. This could have been related to the fact that the absolute amount of work performed with the 2/0/2 tempo was greater than with the 2/0/4 tempo. The exercise literature with regard to IGF-1 responses is equivocal with reports of increases, decreases, and no changes. The increases in IGF-1 observed in this study for the 2/0/2 protocol remain unexplained, but it is possible that reservoirs of IGF-1 are sequestered within the capillary bed walls or other extracellular spaces and are released during exercise. There is also autocrine release and possibly paracrine release from white blood cells and fat cells (4).
It is also important to point out that although subjects were able to perform significantly more work using the 2/0/2 tempo than using the 2/0/4 tempo, their lactate concentrations, heart rate, and RPE were essentially the same between the 2 tempos. Together, this may suggest that in reality it was harder for the subjects to perform the bench press exercise with the slower tempo compared with the normal tempo at the same relative intensity (10). Hatfield et al. (10) have reported that although the absolute RPEs did not differ between their superslow and the volitional protocols, the RPE in relation to the work performed was higher in the superslow condition. The same was true in our study.
The tempos examined in this study are classified as being in the moderate-velocity range and not in the superslow range (15). These particular tempos were chosen because they are commonly used by practitioners in the field. Our results indicate that although individuals can generate slightly more force with the faster tempo (2/0/2), this does not seem to substantially affect the metabolic and hormonal responses to exercise if the exercise is performed at the same relative intensity. Therefore, based on our findings, if practitioners develop exercise programs using either of these tempos, muscle strength and size development is likely to be similar. Whether or not our findings would be the same if the work was performed at the same absolute workload remains to be seen.
The results of the current study indicate the need for future research. Suggested topics include the effects of electromyographic activity during lifting with both tempos because slower tempo training is believed to recruit lower threshold motor units and not the higher threshold units involved with speed and power (10). A study involving the effects of a training program comparing selected tempos would also be useful in addition to the comparison of post-exercise muscle soreness after lifting at different tempos. Finally, a study comparing the effects of unintentional slow velocities vs. intentionally slow contractions velocities on metabolic and hormonal responses is warranted.
Tempo has an effect upon the maximal amount of weight that can be lifted with lifters being able to lift less loads at slower tempos. Generally speaking, individuals may get the same metabolic response to training by using different tempos within the moderate-velocity range, but they will need to use less weight at a slower tempo. We have concluded that using a 2/0/2 or 2/0/4 lifting tempo at the same relative intensity in a single exercise protocol leads to few differences in hormonal, metabolic, and perceptual responses.
The authors thank the subjects who volunteered to participate in these studies. Without their contribution, this study would not have been possible. We would also like to thank Sekeena Bacchus and Sarah Cahill for their assistance with data collection and Dr. Tracey Matthews for her help with the statistical analyses. Finally, we acknowledge the support of the School of Health, Physical Education and Recreation at Springfield College for the Buxton Award, which supplied the funds to complete these studies.
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Keywords:Copyright © 2011 by the National Strength & Conditioning Association.
cadence; endocrine; metabolic; plasma volume change; 1RM