Introduction
The bench press is one of the most used exercises within strength and conditioning practice and programming (22 31 13,21,24,26 13,14 10,11,23 10 11 23
When training for an increase in strength, several training methods and strategies can be adopted. With regard to specificity and technical practice, it is important to perform the full movement itself; however, there is a growing trend to use supplementary or assistance training to develop the muscles, movement patterns, or weak points within a given exercise (29,30,35 30
Elastic resistance training primarily involves the use of elastic bands of varied thicknesses to challenge a movement pattern and align with the force capability of the musculature throughout the range of motion of many movement tasks (29,35 1,8,13,18 28
Elastic assistance training uses an assistance or an overspeed approach during the performance of athletic and strength training movements, allowing an athlete to run faster, jump higher, or lift more weight than they could do without the assistance (7,32 32 7 3
A recent study examined the acute effects of implementing a supportive assistance device called the “Slingshot (SS),” on 1 repetition maximum (1RM) bench press performance in 19 resistance trained male participants (36
We therefore assessed bench press kinematics and neuromuscular activation during maximal and submaximal bench pressing with or without the “SS” in trained powerlifters. Our aim was to use stick point analysis (9,33
Methods
Experimental Approach to the Problem
This study used a within-subjects design to examine the effects of Mark Bell's original “SS” on maximal and submaximal bench press kinematics and neuromuscular activity. The study was designed to assess how using the elastic assistance device, the “SS,” altered neuromuscular recruitment patterns of the prime movers and the kinematics of the bench press during maximal and submaximal efforts. These measurements will allow us to determine the mechanism by which the “SS” may be working and illustrate what affect it may have on muscle recruitment.
Subjects
The methods and procedures implemented within this study were approved by the University of Stirling, School of Sport Research Ethics Committee, and all participants provided written informed consent on recruitment selection. All testing took place at the Gannochy Sports Center—Athlete Performance Laboratory, at the University of Stirling, United Kingdom. Fifteen male competitive powerlifters (Table 1 ; subject characteristics) voluntarily participated in this study. Participants were contacted through word of mouth, social media, and through study advertisement from 2 drug-tested powerlifting federations within the United Kingdom. Participants were selected based on having ≥2 years of powerlifting-based strength training. All participants were considered healthy and injury-free based on their responses to a Physical Activity Readiness Questionnaire and understood no reason as to why their ability to exert maximal bench press force would be limited in any way.
Table 1.: Participant characteristics.* Subject characteristics were measured as mean ± SD
Procedures
The study consisted of 2 laboratory-based trials of ∼1.5 hours each. Trials were scheduled between 7 to 14 days apart and were completed at the same time of day to account for circadian variation (4 2
All bench press attempts were completed on a solid leather competition height bench secured in position inside a FT700 Power Cage (Fitness Technology, Melbourne, Australia), and using an IPF specification Eleiko PL competition barbell (Eleiko, Halmstad, Sweden), Eleiko WL colored training disks (Eleiko), and Eleiko Olympic WL competition collars (Eleiko).
Before commencing the initial trial, participants were provided with a 3-day training and food diary, and asked to complete both diaries in the 2 days leading up to, and day of testing. Participants were advised to maintain their normal diet and training habits and to avoid completing the bench press exercise 48 hours before testing. Before the second trial, participants were provided with their original diaries and advised to replicate their activities to the upmost of their ability.
On arrival to the laboratory, participants provided anthropometric measurements comprising their age (years), body mass (kilograms), and height (centimeters), along with a competition-style bench press 1RM (kilograms) predicted to the best of their ability. Participants were also allowed to select their preferred rack height, and demonstrated their bench press grip width, which was measured and recorded (centimeters) and marked for reference on the barbell using masking tape.
Before commencing any warm-up activities, participants were familiarized with the testing protocol and requirements, and allowed to ask any questions or for any further information, if required. During the initial phase of the warm-up, all participants were required to familiarize themselves with the sEMG normalization procedure by completing controlled and consistent bench press repetitions using the empty barbell to a metronome set at 30 b·min−1 , before loading. During this familiarization, a clearly audible metronome was played through a pair of speakers, and participants were required to complete a full competition style set-up, unrack the barbell, and perform as many repetitions as they deemed necessary until they felt confident executing the bench press movement to the rhythm of the metronome. Each time the metronome sounded indicated a change of phase (eccentric:concentric), requiring a controlled time period of 2 seconds per phase.
After the metronome familiarization, the barbell was loaded for participants and they performed repetitions at various increments of their choosing. Number of sets, repetitions, and loadings were recorded on a data collection sheet for replication in the subsequent trial and rest intervals of 2 minutes were provided throughout the warm-up. For normalization purposes, participants were recorded performing 1 set of 5 repetitions at 70% of predicted 1RM to the 30 b·min−1 metronome, following the criteria highlighted above (6
Once participants exceeded 90% predicted 1RM, all attempts were considered “1RM attempts” and were completed between 5-minute rest intervals and to correct referee commands and competition rules (IPF, 2015). Participants proceeded with 1RM attempts in increments of their choosing and in agreement with the primary investigator until they reached muscular or technical failure. In all instances, 1RM was achieved between 3 and 5 attempts. Attempts were disqualified if the participant failed to successfully perform the repetition or if they failed to meet all competition requirements for successful bench press performance (IPF, 2015) (Figure 1 ). Once participants had established a 1RM, they performed 3 consecutive paused repetitions at 87.5% 1RM to demonstrate execution of a predicted 3 repetition maximum (3Rep) with consideration to fatigue accumulated following the 1RM protocol (2 2
Figure 1.: “Slingshot” placement during a representative repetition. Subjects were instructed to perform the “SS” repetitions to the same International Powerlifting Federation (IPF) standards as in the previous “Raw” trials.
Following the 7- to 14-day interval, participants returned to the laboratory and completed the SS trial. Participants were provided with an introduction to the SS, and, identical to trial 1, participants' anthropometric characteristics were taken and a refamiliarization to the procedures was provided before commencing the warm-up. Several different size selections were provided for the “SS” device, and were fitted to each participant according to the manufacturer's instructions. The same warm-up protocol was followed, and an identical rack height and grip width was implemented. All warm-up before, and including normalization repetitions were taken without the use of the “SS,” and all repetitions performed following the 70% normalization were completed using the “SS.” The “SS” was worn across the elbow joint as recommended by the product manufacturers, and to avoid disruption to EMG signals on the triceps and pec placements (Figure 2 ). The achieved Raw 1RM weight was performed as one of the “SS” 1RM attempts (Raw max/SS), participants then proceeded to add weight and follow the same protocol as the “Raw” trial until a separate “SS” 1RM was achieved. Participants' 3Rep and 8Rep weight were established using 87.5% and 70% of the achieved “SS” 1RM, respectively, and were performed in the same manner described for the “Raw” trial. All attempts throughout both trials were performed to the nearest 1 kg.
Figure 2.: Electrode placement and positioning of the “Slingshot (SS).” Participants were instructed to wear the “SS” with the crease centered at the elbow. Electrodes were placed as described in the methods to ensure that the “SS” did not disrupt the electrodes during bench pressing.
Surface EMG amplitude was collected by skin surface electrodes (SilveRest, Vermed, VT) from the pectoralis major, anterior deltoid, and triceps brachii of the participants' dominant side during all repetitions using a BioPac MP100 (BioPac Systems, Inc., Santa Barbara, CA, USA). Reference signals were provided via skin surface electrodes placed on the clavicularis and patella. Before applying the electrodes, the skin surface was prepared for collection by shaving, slightly abrading using sandpaper, and wiped with alcohol swabs (PDI Healthcare, Orangeburg, NJ, USA), in line with SENIAM guidelines (16 19 Figure 2 ). Electrode placement for both the anterior deltoid and triceps brachii were in line with recommendation by Perotto and Delagi (25
A Celesco PT5A-125-S47-UP-10K-M6 linear transducer (Celesco, Toronto, ON, Canada), connected to a BioPac MP100 data capture unit (BioPac Systems, Inc.), was secured to the top of the power rack to measure participants' average barbell velocity (m·sec−1 ) and bar displacement (centimeters) during all bench press attempts. During both “Raw” and “SS” trials, a Velcro strap attached to the transducer cable was secured in a consistent, slightly off center placement on the barbell. The position of the transducer was adjusted appropriately for each participant so that the cable ran vertically during bench press execution. As participants performed bench press repetitions, the velocity and displacement of the barbell was recorded using the Acqknowledge software for Windows (BioPac Systems, Inc.) and saved for offline analysis.
All data were analyzed using the Acqknowledge software for Windows (BioPac Systems, Inc.). Repetition phases were defined in accordance with (9,34 15 6
Analysis of the transducer data was performed by highlighting only the concentric phase of the repetitions. Phases were defined in accordance with Van den Tillaar and Ettema (34 −1 , indicating a change of direction. For maximal attempts, the phases of the concentric portion of the bench press were defined as per Van Den Tillaar and Ettema (34 Figure 3 for representative trace). This involved defining the beginning of the prestick period (phase 1) by identifying the point at which velocity was 0 m·sec−1 at the end of the eccentric phase, identifying the stick point and beginning of the stick period (phase 2) as the point of peak velocity during the concentric phase, and identifying the poststick period (phase 3) as the point at which acceleration again crossed 0 m·sec−2 . The lift ended when velocity reached 0 m·sec−1 at the end of the concentric phase. Each phase and/or repetition was analyzed individually for total time (seconds), average bar speed (m·sec−1 ), and the stick point was identified (meters) comparative to the total displacement.
Figure 3.: Defining the phases of maximal bench press attempts. Figure 3 illustrates a representative trace of acceleration, velocity and displacement during a 1 repetition maximum (1RM) attempt. The beginning of the prestick period (phase 1) was identified as the point at which velocity was 0 m·sec−1 at the end of the eccentric phase. The stick point and the beginning of the stick period (phase 2), was identified as the point of peak velocity during the concentric phase. The poststick period (phase 3) began when acceleration again crossed 0 m·sec−2 . The poststick period ended when velocity reached 0 m·sec−1 at the end of the concentric phase.
Statistical Analyses
All statistical analyses were carried out in GraphPad Prism (GraphPad Software, La Jolla, CA, USA). Where 2 groups were compared, a 2-tailed t -test was performed. Where more than 2 groups were compared, a 1-way analysis of variance (ANOVA) was used with a Tukey's HSD test. Where multiple comparisons were made across groups, a 2-way ANOVA was performed with a Bonferroni's multiple comparisons test. Normality of data was tested using D'Agostinio-Pearson omnibus normality test. Where data were not normally distributed, then the nonparametric 2-tailed t -tests were performed. When multiple comparisons were made on nonnormal data, then a Friedman test was used with a Dunn's multiple comparisons test. All data were reported as mean ± SEM and significance was set as p ≤ 0.05. Correlations were determined via a simple linear regression.
Results
All participants displayed an increase in absolute bench press performance while using the “SS” from 139.7 ± 4.34 kg “Raw” to 160.4 ± 4.43 kg “SS” for an average increase of ∼20 kg (Figure 4A ). The absolute gain from the “SS” was not related to the amount lifted (Figure 4B ) but instead was highly correlated to the individuals bodyweight (R 2 = 0.334), indicating that despite all participants wearing an appropriately sized device, the larger participants were able to gain more from the “SS” (Figure 4C ). The “Raw” 1RM corresponded closely to the calculated “SS” 3Rep (Figure 4D ). These data were plotted and correlated revealing that there was a highly significant correlation between participant's “Raw” 1RM and “SS” 3Rep (R 2 = 0.954) (Figure 4E ).
Figure 4.: The “Slingshot” (SS) increases the bench press 1 repetition maximum (1RM) in a manner correlated to body mass. Fifteen trained powerlifters underwent rep max testing on 2 occasions separated by 7–14 days. The “Raw” repetition maximum (1RM) was determined without any assistance and the SS repetition maximum was determined while wearing the “SS.” After the 1RM testing, 3 repetitions (3Rep) were performed at 87.5% of the achieved 1RM followed by 3 sets of 8 (8Rep) at 70% of the achieved 1RM. The mean weight lifted in each of these conditions is plotted in (A) with the individual 1RM data plotted on the inset graph. The absolute gain from wearing the “SS” (the difference between Raw and SS trials) was plotted against the Raw 1RM achieved (B) and against the body mass of the individuals (C). The individual data for the Raw 1RM and the weight lifted on the 3Rep SS trial were plotted (D) with a linear regression of these variables plotted in (E). *Significantly different from corresponding “Raw” condition (as assessed by paired t -test between respective “Raw” and “SS” conditions). Significance was determined as p ≤ 0.05.
During maximal 1RM bench press attempts, “Raw” normalized triceps RMS (169.64 ± 15.26%) was significantly higher than both “Raw max/SS” and “SS” conditions (87.28 ± 5.84% and 115.84 ± 10.64%) (Figure 5A ). Normalized RMS for the pectoralis was significantly lower in the “Raw max/SS” condition compared with the “SS” condition (90.83 ± 6.97% vs. 117.8 ± 11.27%) during 1RM attempts (Figure 5A ). Normalized RMS for all muscles (grouped) was significantly reduced during 1RM performance for “Raw max/SS” (95.58 ± 5.47%) than during the “Raw” condition (138.82 ± 9.42%) (Figure 5A ). Normalized triceps RMS was also observed to be significantly higher during the “Raw” condition (126.02 ± 9.19%) than the “SS” condition (83.12 ± 9.97%) during a set of 3 repetitions (Figure 5B ), and during both set 1 (108.15 ± 6.25% vs. 75.96 ± 7.36%) and set 3 (115.35 ± 7.48% vs. 84.37 ± 8.45%) of the multiple sets of 8 repetitions (Figure 5C ).
Figure 5.: The “Slingshot” (SS) reduces surface electromyographic (sEMG) amplitude of the triceps brachii at all intensities. The “Raw max/SS” was performed during the warm-up of the SS trial day and consisted of performing the previous session's raw 1RM while wearing the “SS.” Surface EMG amplitudes were recorded during all sets and reps as described in the Methods. All data presented are root mean square (RMS) processed and normalized to the 70% normalization set. A) The sEMG amplitudes recorded during repetition maximum testing; (B) sEMG amplitudes recorded during the set of 3 repetitions at 87.5%; and (C) sEMG amplitudes recorded during the 3 sets of 8 repetitions at 70%. Φ = “Raw” is significantly different from both “Raw max/SS” and “SS” (as assessed by multiple comparisons); α = significantly different from “SS” (as assessed by multiple comparisons); § = significantly different from “Raw” (as assessed by multiple comparisons); * = significantly different from “raw” (assessed by paired t -test). Significance was determined as p ≤ 0.05. Tricep = triceps brachii, pec = pectoralis clavicularis, Delt = anterior deltoid, grouped = sEMG grouped for all 3 muscles assessed.
Average barbell velocity was significantly greater across the whole concentric phase by ∼3-fold for the “Raw max/SS” condition (0.29 ± 0.02 m·sec−1 ) compared with the “Raw” and “SS” conditions (0.11 ± 0.01 m·sec−1 and 0.10 ± 0.01 m·sec−1 ) (Figure 6A ). The peak velocity during the maximal attempts was significantly higher in the “SS” condition compared with the “Raw” condition (0.31 ± 0.02 m·sec−1 vs. 0.27 ± 0.02 m·sec−1 ), as was the average velocity of phase 1 (Figure 6A ). There is a trend for phase 3 to have a lower velocity in the “SS” condition compared with “Raw.” There is a high degree of variability between the “SS” and “Raw” conditions when plotting these data as individual responses, while during phase 1 there is a consistent increase in phase 1 velocity (9 subjects increase) when wearing the “SS” (Figure 6B ).
Figure 6.: The “Slingshot (SS)” improves peak barbell velocity on maximal efforts and maintains mean barbell velocity in multiple repetition sets. Barbell velocity was tracked during all movements using a vertical transducer. The phases of the bench press were determined by assessing the acceleration curves with the stick period defined as the period between negative and positive barbell acceleration. A) Barbell velocity during rep max testing. B) Individual changes in barbell velocity between “Raw” and “SS” trials assessed by phases of the maximal effort. C) Barbell displacement during maximal efforts with the displacement at which the stick point occurs and also the displacement over which the stick period lasts also plotted. D) The % of the total displacement at which the stick period begins (stick point) and the % displacement over which the stick period lasts plotted as individual responses from the “Raw” to the “SS” trials. E) Average barbell velocity for each repetition of the set of 3 reps at 87.5%. F) The % decrement in barbell velocity from repetition 1 to repetition 3 on the “Raw” and “SS” trials. G) Average barbell velocity for the first and last rep of the first and last set of the 3 sets of 8 repetitions at 70%. H) The % decrement in barbell velocity from repetition 1 to repetition 8 on the third set of the “Raw” and “SS” trials. Φ =“Raw” is significantly different from both “Raw max/SS” and “SS”; α = significantly different from “Raw” (assessed by multiple comparisons); ε = significant difference between 2 bars (assessed by multiple comparisons); * = significantly different from “Raw” (assessed by paired t test). Significance was determined as p ≤ 0.05.
The displacement data demonstrates that there was no effect of wearing the “SS” on total displacement indicating that hand position was replicated accurately between trials and that the “SS” did not affect the range of motion (Figure 6C ). However, the “SS” significantly altered the displacement at which the stick point occurred (Figure 6C ). The effect was small, ∼1 cm higher in the concentric phase, but very consistent with 12 of 15 subjects demonstrating an upward shift in the start of the stick point (Figures 6C, D ). The sticking period tended to occupy a greater proportion of the concentric phase while wearing the “SS”; however, this did not reach significance. While not significant, when the individual data were plotted as percentage of the total displacement, there was a similar trend but a high degree of intersubject variability, with 7 subjects demonstrating an increase and 8 subjects demonstrated a decrease in the stick period length while wearing the “SS” (Figure 6D ).
No significant differences were found for average barbell velocity (m·sec−1 ) during reps 1 and 2 of the 3Rep; however, the average barbell velocity was significantly faster for the “SS” condition than the “Raw” condition (0.21 ± 0.02 m·sec−1 vs. 0.18 ± 0.02 m·sec−1 ) during rep 3 of the 3Rep (Figure 6E ). Similarly, the change in barbell velocity (%) between reps 1 and 3 of the 3Rep were significantly lower in the “SS” than the “Raw” condition (−15.72 ± 5.36% vs. −25.57 ± 9.4%) (Figure 6F ). Average barbell velocity was significantly faster during the “SS” than the “Raw” condition for both set 1 rep 8 (0.35 ± 0.04 m·sec−1 vs. 0.30 ± 0.04 m·sec−1 ) and set 3 rep 8 (0.34 ± 0.07 m·sec−1 vs. 0.26 ± 0.03 m·sec−1 ) during the multiple sets of 8 repetitions (Figure 6G ). Similarly, the change in barbell velocity (m·sec−1 ) between reps 1 and 8 of the multiple sets of 8 were significantly lower in the “SS” than the “Raw” condition (−19.38 ± 4.4% vs. −31.18 ± 4.82%) (Figure 6H ).
To determine the mechanism behind the improved 1RM performance while wearing the “SS,” we split the analysis of the prime mover RMS over the 3 phases of the bench press; prestick period [1], stick period [2], and poststick period [3]. These data revealed that there was no effect of the “SS” on pectoralis (Figure 7B ) or deltoid (Figure 7C ) RMS activation. However, the triceps RMS was significantly lower during the stick [2] and poststick [3] periods (Figure 7A ).
Figure 7.: The “Slingshot (SS)” reduces surface electromyographic (sEMG) amplitude of the triceps brachii during a maximal effort. Surface EMG amplitudes were recorded during repetition maximum testing as described in the Methods. All data presented are root mean square (RMS) processed and normalized to the 70% normalization set. A) sEMG amplitudes of the triceps brachii, (B) sEMG amplitudes of the pectoralis clavicularus, and (C) sEMG amplitudes of the anterior deltoids. α = significantly different from “SS” (as assessed by multiple comparisons p ≤ 0.05).
Discussion
This is the first study to assess the impact of the “SS” bench press training aid on bench press kinematics and neuromuscular activity in comptetitive powerlifters across a range of intensities. The “SS” was found to be an effective elastic assistance device for enhancing 1RM bench press performance in all participants, on average producing a fixed absolute increase of ∼20 kg. This elastic assistance allowed the “Raw” 1RM to be lifted with an average velocity ∼3× faster than the “Raw” 1RM performed unassisted. The increased velocity while wearing the “SS” occurred despite significantly reduced RMS in the triceps brachii. Furthermore, when intensity was matched (same relative %1RM with or without the “SS”), the RMS of the triceps was reduced at all intensities. During both the multiple repetition conditions (3Rep/8Rep), the last rep was performed with a higher velocity than the corresponding “Raw” condition. This preservation of barbell velocity throughout a set may be indicative of reduced fatigue (27
Components of the velocity data from our study are somewhat reminiscent of the velocity data obtained from performing the bench press with chain weight (5
One possibility is that the “SS” may alter the mechanics of the bench press by pulling the elbows into a more mechanically advantageous position. Van den Tillaar and Ettema (34
The study by Ye et al., (36 36
Practical Applications
Aside from suggesting how the “SS” works, our data also suggest some potential uses for the device in training. Some researchers have theorized that the benefit of elastic training is that it allows for similar forces to be produced but at faster velocities (20
In summary, the acute increases observed in bench press performance resultant of using the “SS” suggest that it may be an effective training device for speed training and deloading the bench press exercise during a variety of intensities while maintaining the full range of motion of the traditional format of the bench press.
Acknowledgments
This study was conducted without any financial support and we have no conflicts of interest. The results of this study do not constitute endorsement of the product by the authors or the NSCA. The authors gratefully acknowledge expert technical assistance for Mr Chris Grigson. The authors are indebted to the volunteers who gave their time to this study.
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