The training intervention required lifting sessions 5 days a week for 6 weeks. Subjects performed lower-body exercises on Tuesdays, Fridays, and Sundays and upper-body exercises on Mondays and Thursdays. Subjects typically performed 5–6 exercises per session, focusing primarily on free-weight dynamic exercises that incorporate all major muscle groups, such as competition squats, competition deadlifts, competition bench presses, bench press variations, dynamic upper-back exercises, tricep extensions, and core exercises. Assisted lower-body exercises typically comprised hip extension/flexion and glute-hamstring raises.
All subjects performed the same workout, except for the bench press exercise, on the second upper-body day of the week (Thursday). On Thursday, the FB group used the FB during the 3-position pause bench press exercise. This style of training is a common practice for powerlifters because, per the rules of the USAPL competition bench, lifters are required to hold the barbell at a motionless pause on the chest before a chief referee signals a press command (19). The traditional group performed the 3-position pause bench press exercise with a TB. For the FB group, the 3-position pause bench press exercise was performed by a controlled lowering of the barbell during the eccentric phase, followed by an isometric hold at the respective joint position and a squeezing of the springs for 2 repetitions at each position. For each of the 3 positions, the lifters were instructed to “squeeze” and “spread” the handles on the FB from a normal position grip to a narrow position grip (Figure 5) on the barbell. The spring-loaded 2 × 4 inch handgrip (Figure 1) allowed for movement along the barbell in the lateral direction. For the TB group, subjects also were instructed to perform the 3-position pause bench press exercise with a controlled lowering of the barbell in the eccentric phase and a pause at each of the 3 bench positions. For both groups, during the concentric phase, subjects pressed the barbell as quickly as possible to replicate a typical bench pressing movement (30). This cadence is commonly used for specialty barbells with components of instability (31).
The initial loading for the 3-position pause bench press, using the FB, was 60% of subjects' current 1RM for the bench press. Subjects used an autoregulated approach based on weekly performance, which resulted in the loading's being kept the same or having a 5-lb increment progression. This loading progression is similar to what has been reported in the literature (45). The initial loading percentage was chosen during pilot testing, when several advanced-level lifters performed a near-maximal effort set of 3 repetitions with the FB and then compared that weight against their competition maximum. This prescribed load is consistent with the methods used by Ostrowski et al. (31) and Dunnick et al. (11) that used UL for the barbell bench press.
Subjects were advised to maintain their normal diet and to avoid taking any supplements during the study. Self-reported food records were collected during the first (week 1) and final week (week 6) of the study. Subjects were instructed on how to properly complete a 3-day dietary recall log to include all food items and their respective portion sizes consumed. Dietary analysis software (myfitnesspal) was used to analyze dietary recalls to assess potential differences in total energy and macronutrient intake between groups (Table 2).
Data analysis was performed using IBM SPSS, Version 24.0 (SPSS, Inc., Chicago, IL, USA) software for Windows. Descriptive data for subject characteristics and experimental variables were calculated as mean values and SDs. Normality of the distributions was tested using a Shapiro-Wilk test (p ≤ 0.05). All the data satisfied normality. To test for pre-existing differences before the program (Table 3), we used independent t-tests to examine the difference between the groups for body weight, 1RM bench press, and peak force.
Dependent t-tests were used to calculate within-group differences between pretest and posttest scores for 1RM bench press, peak force at 3 positions, and peak impulse at 3 positions. For the 1RM bench press test, a 1-way analysis of covariance (ANCOVA) was used to examine the difference between the groups, with the bench press delta score as the dependent variable, group as the fixed factor, and pretest bench press score as the covariate. The homogeneity of regression assumption tested for the interaction between the group and pretest bench press score. For peak force and peak impulse, a 1-way multivariate ANCOVA was used to examine differences between the groups, with all 3 position delta scores as the dependent variables, group as the fixed factor, and pretest scores as the covariate. If a significant Wilks lambda was found, individual 1-way analysis of variances were calculated to examine the differences between the groups for the respective dependent variable. The homogeneity of regression assumption tested for the interaction between the group and pretest delta scores for each peak force and peak impulse position. The multicollinearity assumption was tested using collinearity diagnostics and an examination of the variance inflation factor (VIF) across the 3 peak force delta scores and 3 peak impulse delta scores. A VIF >10 was a violation for this assumption.
As per Beck (2), a priori sample size was calculated for a 1-way ANCOVA with the pretest 1RM bench press as a covariate. To detect a potential moderate 1.4 Cohen's d effect size for recreationally trained (32) subjects at the α = 0.05 significance level, a total sample size of 10 subjects, 5 per group, produced an actual power of 0.51. All subjects were familiar with the powerlifting program and had been training consistently for ≥2 years; however, as a group, they were classified as recreationally trained due to the overall team's modest bench press per body weight (BP/BW) 1RM score of 1.18.
Both groups demonstrated 100% compliance to the training program. Raw data values, delta scores, post-1RM bench press per body weight scores, and within-group Cohen d effect sizes for maximum 1RM bench press strength are presented for each training group in Table 4. Cohen's d within-group effect size was calculated by the difference between pretest and posttest scores, divided by the SD of the pretest (8).
One Repetition Maximum Bench Press
Individual spaghetti graphs are presented for each subject as a result of the 6-week training program (Figure 6). There was no significant difference between the groups across delta score, using pretest bench press as a covariate (p = 0.589,
= 0.044). There was a significant (p = 0.006) increase for the FB group before (100.9 ± 41.6 kg) and after (107.7 ± 43.2 kg) training intervention. There was a nonsignificant (p = 0.23) increase for the TB group before (105.9 ± 53.2 kg) and after (110.4 ± 55.9 kg) training intervention.
There were no significant differences in peak force between the groups for bench position 1 (p = 0.183,
= 0.323), position 2 (p = 0.360,
= 0.169), or position 3 (p = 0.702,
= 0.032). There was a nonsignificant increase for the FB group before and after training intervention for position 1 (mean difference 57.6 ± 61.1, p = 0.103), position 2 (mean difference 69.4 ± 118.7, p = 0.26), and position 3 (mean difference 115.4 ± 123.5, p = 0.105). There was a nonsignificant decrease for the TB group before and after training intervention for position 1 (mean difference −35.6 ± 78.0, p = 0.365) and position 2 (mean difference −31.8 ± 64.4, p = 0.332) as well as a significant increase for position 3 (mean difference 81.4 ± 36.1, p = 0.007) (Figure 7).
Figure 8 illustrates peak impulse output by bench press position across both groups, before and after training intervention. There were no significant differences in peak impulse between the groups for bench position 1 (p = 0.184,
= 0.322), position 2 (p = 0.321,
= 0.195), or position 3 (p = 0.667,
= 0.040). There was a nonsignificant increase for the FB group before and after training intervention for position 1 (mean difference 74.7.6 ± 71.1, p = 0.078), position 2 (mean difference 81.3 ± 115.8, p = 0.191), and position 3 (mean difference 113.8 ± 120.0, p = 0.101). There was a nonsignificant decrease for the TB group before and after training intervention for position 1 (mean difference −29.4 ± 86.2, p = 0.487) and position 2 (mean difference −21.9 ± 66.7, p = 0.502) as well as a significant increase for position 3 (mean difference 81.7 ± 49.2, p = 0.021).
The aim of the current study was to examine the effects of a 6-week training program that uses the FB as compared to the TB in the bench press exercise in a sample of collegiate club powerlifters. The training programs for each group were equal in duration, volume, and loading. Maximum strength, peak force, and peak impulse were tested before and after training intervention. The major findings were that 1RM strength increased for both groups, with no significant differences between the groups. This supports our primary hypothesis. An increase in peak force at all 3 positions for the FB group and for only position 3 for the TB group partially supports our second hypothesis. Our finding of no significant difference between peak impulse at any bench position across the groups does not support our final hypothesis.
The ∼7- and 5-kg increase in strength for the FB and TB groups, respectively, is comparable with a previous linear periodized 6-week strength training program for the bench press exercise (45). Both groups showed improvement in 1RM strength; however, the use of the FB did not further increase performance. Despite the lack of significance between the groups, a few findings for the 1RM data should be emphasized. For example, all subjects in the FB group increased in maximum strength with minimal to no change in body weight after training. A closer examination shows that subjects 1 and 4 had substantial increases of 9 kg. Notably, Subject 1 is an advanced bench presser with a BP/BW of 1.7. Overall, both groups reported a small within-group Cohen d effect size because of a large amount of pretest variability for each group. The authors understand the cautions related to reporting within-group effect size (8). A review by Dankel et al. (8) highlights the widespread misuse of effect size in low sample-size studies and how its misuse affects the interpretation of the findings. A recommendation is to report all the raw data values, such as those seen in Table 4. A supporting recommendation from Weissgerber et al. (44) is to report raw data not only in table form but also in graphical form (Figure 6), which allows readers to evaluate the trends of the study and to make their own interpretations.
A nonsignificant increase in force production of 16, 17.5, and 21.5% occurred at positions 1, 2, and 3, respectively, for the FB group. There are 2 possible explanations for this finding. First, this may have reflected the lifters' improved ability to increase force in the vertical direction. The FB provides a unique feature providing medial-lateral resistance along the horizontal axis of the barbell, which may train the lifter to produce more lateral and vertical force generation (10). Second, the moderate instability from the FB may have forced lifters to maintain tightness throughout the training repetitions, which improves the lifters' ability to prevent their muscles from going lax during the bench press, thus producing greater transfer of force in the vertical direction. This is supported in previous studies that used UL in the bench press, which created unwanted perturbation of the barbell, particularly when lifters perform the concentric phase as quickly as possible (31). The decrease in force production for the TB is more difficult to explain. The TB group reported decreases of 7 and 6% at positions 1 and 2, respectively, with a significant within-group increase of 14% at position 3. The decrease in force production for positions 1 and 2 was unexpected; however, the precipitous drop for Subject 10 (delta z-scores = −2.27, −1.47) contributed to this occurrence.
Similar to the findings of Clark et al. (7), although we graphed the impulse (N·s), the data indicate the lowest level of force at position 1, a progressive increase at position 2, and the largest force production at position 3. Our final hypothesis was not supported because there was no significant difference in peak impulse between the groups at any position. A possible rationale for this finding is that the 1-second time interval used for the peak impulse calculation is too short of an interval to accurately assess the ability to maintain peak tension at each position. Thus, we suggest that a longer time interval, such as 3–5 seconds, should be used to more accurately measure peak impulse or the ability to maintain tension near peak force for a given amount of time. If lifters improve their ability to maintain peak force over a specific interval, subjects could keep tension and stability for heavy intensities (>90% 1RM) and repetitions, approaching muscular failure.
The 3-position pause bench press was chosen because it forced the subject to control the barbell at each theoretical sticking point, and the mounted force plate allowed us to test force production at each point. The primary goal of the training program was to increase bench press performance, which, for powerlifters, is 1 of the 3 primary competition lifts. Furthermore, the bench press exercise is a common focus of research that examines the multiple variables that affect bench press performance, including time under tension (36), tempo (17,35), contraction type (21), range of motion (7,28), surface stability (15,26,33), barbell stability (11,29,31), bar width (13), and grip width (14,34). Despite a large body of research on the multiple ways to improve bench press performance, one consistent challenge is to increase force production through the sticking point. The sticking point, or sticking region, has an ambiguous definition, but a recent work by Kompf and Arandjelovic (24) defined it as the point at which failure occurs when exercise is taken to the point of momentary muscular failure. Previous definitions include the point where the initial deceleration of the barbell velocity occurs during the concentric phase (42).
The sticking point is complex and exists across all 3 powerlifting competition lifts (25). Computer-based models illustrate its complexity, showing that 2 lifters with the same level of bench press strength have sticking points at 2 separate ranges of motion (1). Specific to the bench press, the sticking point can vary across lifters due to multiple factors, such as the lifter's anthropometry (5), training status (12), success of the lift (41), and grip width (14) as well as how the bench is performed, i.e., with or without countermovement (42). Increased knowledge of the biomechanics and physiological mechanisms of the sticking point has resulted in various training techniques to improve sticking point strength. Coaches should implement a variety of training methods to improve a lifter's “weakest link.” Training methods such as accommodating resistance, partial range of motion training, alterations in technique, and target muscle strengthening isolation work are worthy of consideration (25).
There are several limitations to the current study. First, the authors recognize the low statistical power of the design, which is due to the small sample size. We chose to only include subjects who were familiar with the powerlifting training program and who could adhere to the team's training schedule to reduce variability and drop out. We believe that requiring participation in the powerlifting club for 1 year increased the adherence rate to the program and avoided disruptions to team training sessions, which, in turn, reduced our total sample size. Second, the novelty of the FB coupled with what can be considered a short training period may not have allowed the subjects sufficient familiarity with the adaptations of the bar. Most linear periodization programs are 9–12 weeks in duration (16). All subjects in the FB group were familiar with the competition bench press but had never used the FB. A longer training intervention would allow subjects to become more familiar with the articulating handles and to become more adept at using the barbell correctly. A final limitation is the heterogeneity of the pretesting data. The sex differences created a large spread in the variability of pretest scores, which reduced the design sensitivity. Although the authors matched the subjects on pretest 1RM bench to increase sensitivity, a more homogeneous group would likely have reduced the spread of scores.
Future research should include electromyography analysis to better quantify muscle activation during use of the FB or other specialty bars on the commercial market (9). It is likely that the resisted glenohumeral horizontal adduction and internal rotation would stimulate a large recruitment of the pectoralis major muscle, which is the prime mover in the bench press exercise (39).
Unstable load training, particularly the use of specialty bars that provide instability at the barbell itself, is a recent focus in sports science (6,31). The current study supports the use of the FB to increase maximum strength and force production to levels that are comparable with TB training. The moderate level of instability provided by the articulating handles of the FB allows lifters to apply force in the medial-lateral and vertical directions. This, in conjunction with the ability to adequately load the FB in a manner that is comparable with that of a TB, provides an alternative method to increase upper-body strength in the bench press exercise. Training with the FB will train the lifter to apply lateral and medial forces, producing more vertical force during concentric contraction (10). This can be a practical application of the FB in regard to exercise prescription. The increase in muscular strength and force production at all 3 bench positions at the conclusion of the intervention for subjects in the FB group demonstrates that the FB can be used as an assistance exercise for the bench press. Nevertheless, the lack of statistical differences between the FB and TB groups demonstrates that there are no significant advantages to using the FB in place of the TB for the bench press exercise.
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Keywords:Copyright © 2018 by the National Strength & Conditioning Association.
specialty bars; instability; force plate; unstable load; strength