Influence of the “Slingshot” Bench Press Training Aid on Bench Press Kinematics and Neuromuscular Activity in Competitive Powerlifters

Abstract Dugdale, JH, Hunter, AM, Di Virgilio, TG, Macgregor, LJ, and Hamilton, DL. Influence of the “Slingshot” bench press training aid on bench press kinematics and neuromuscular activity in competitive powerlifters. J Strength Cond Res 33(2): 327–336, 2019—This study examined the acute effects of the “Slingshot” (SS) on bench press performance, prime mover surface electromyographic (sEMG) amplitude, and barbell velocity during maximal and submaximal bench pressing in competitive male powerlifters. Fifteen male powerlifters (mean ± SD; age: 27.05 ± 5.94 years; mass: 94.15 ± 13.43 kg; 1 repetition maximum [1RM] bench press: 139.7 ± 16.79 kg) participated in the study. Bench press strength, average barbell velocity, and sEMG amplitude of the prime mover muscles (triceps brachii, pectoralis major, and anterior deltoid) were measured during 2 conditions; “Raw” (without use of any assistance) and “SS” (using the “Slingshot” to perform both the weight achieved during “Raw” 1RM testing [Raw max/SS], and absolute 1RM using the “SS”). The results showed that the “SS” significantly increased bench press 1RM performance by a mean ± SD of 20.67 ± 3.4 kg. Barbell velocity and stick point analysis indicate that this improvement is likely driven by an increase in peak and prestick barbell velocity as triceps root mean square (RMS) was lower throughout all rep max phases with the “SS.” The “SS” also caused reductions in RMS, specifically of the triceps at all rep ranges but barbell velocity was better maintained in the last reps of all sets. These data indicate that the “SS” specifically deloaded the triceps muscle throughout all rep ranges and provide assistance to maintaining barbell velocity under fatigue during later repetitions of multiple repetition sets. The “SS” training aid could therefore be used in deload phases of bench press training or as an overreaching and velocity training aid.


Introduction:
1 The bench press is one of the most utilised exercises within strength and 2 conditioning practice and programming (5). Similar to other free-weight 3 resistance exercises, the bench press is utilised for developing maximal strength, 4 power, and hypertrophy (30). The bench press is also one of the three 5 competition lifts within the sport of powerlifting (IPF, 2015). However, the 6 popularity of the bench press is due to its ability to develop the strength, power, 7 and hypertrophy of the prime movers: the pectoralis major, anterior deltoid, and 8 triceps brachii (14,21,23,25). Several studies demonstrate the transfer of bench 9 press strength to improvements in motor unit recruitment through various 10 planes of the shoulder (14, 15), and more importantly for athletic performance, 11 strength in the bench press is an indicator of performance in strength and power 12 sports (11,12,22). Therefore developing strategies to improve bench press 13 performance has the potential to improve performance across a range of sports 14 including but not limited to powerlifting, discus throwing (11), swimming (12), 15 and kayaking (22). 16 When training for an increase in strength, several training methods and 17 strategies can be adopted. With regards to specificity and technical practice it is 18 important to perform the full movement itself, however there is a growing trend 19 to utilize supplementary or assistance training to develop the muscles, 20 movement patterns, or weak points within a given exercise (28,29,34). A recent 21 survey of competitive powerlifters demonstrated that over 50% are utilizing 22

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Copyright ª 2017 National Strength and Conditioning Association resistance bands in their bench press training, more so than alternative 23 supplementary training methods such as the use of chains (29). 24 Elastic resistance training primarily involves the use of elastic bands of varied 25 thicknesses to challenge a movement pattern and align with the force capability 26 of the musculature throughout the range of motion of many movement tasks (28,27 34). Several studies demonstrate that the use of combined elastic resistance 28 training in the bench press improves the development of upper body strength (1, 29 9, 13, 18), and in addition, a recent meta-analysis supports the efficacy of 30 variable resistance training methods (use of bands and chains) to improve 31 measures of maximal strength (27). Despite the increased popularity and 32 evidence for the use of elastic resistance training, far less attention has been 33 focused on elastic assistance training. 34 Elastic assistance training utilises an assistance or an over-speed approach 35 during the performance of athletic and strength training movements, allowing an 36 athlete to run faster, jump higher, or lift more weight than they could do without 37 the assistance (8,31). Several studies demonstrate that elastic assistance acutely 38 improves jump height (31) and sprinting performance (8), whilst chronic jump 39 training with elastic assistance for 4-weeks significantly improved jump 40 performance compared to training without assistance (3). Relative to research 41 on elastic resistance devices, much less attention has been given to the 42 implementation of elastic assistance devices for upper-body strength 43 performance. 44 A recent study examined the acute effects of implementing a supportive 45 assistance device called the 'Slingshot', on 1RM bench press performance in 19 46

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Copyright ª 2017 National Strength and Conditioning Association resistance-trained male participants (35). The study observed the effect of the 47 'Slingshot' in comparison to traditional 'Raw' bench press performance, and 48 report significant increases to 1RM and barbell velocity associated with trends 49 for decreased EMG amplitude for both the pectoralis major and triceps brachii. 50 They report that all participants showed an increase in absolute 1RM 51 performance by an average of ~16Kg whilst wearing the 'Slingshot', and that 52 participants were able to execute their 'Raw' 1RM weight at significantly higher 53 barbell velocity and power output when using the 'Slingshot'. However, when the 54 relative intensity was matched between the absolute 'Raw' vs. 'Slingshot' 1RM 55 average barbell velocity and average power output were not statistically 56 different and there was a trend for the prime mover normalised EMG amplitude 57 to be lower whilst wearing the 'Slingshot' despite the heavier load. These data 58 indicate that the 'Slingshot' was assisting participants to lift either heavier loads 59 or equal loads at a greater velocity, whilst the trends for decreased EMG 60 amplitude suggest potential de-loading in the prime movers. 61 We therefore assessed bench press kinematics and neuromuscular activation 62 during maximal and submaximal bench-pressing with or without the 'Slingshot' 63 in trained powerlifters. Our aim was to use stick point analysis (10, 32) in 64 conjunction with EMG assessments to try to understand the mechanism by 65 which the 'Slingshot' improves 1RM, and the influence it may have on matched 66 intensity submaximal sets. We hypothesized that the improvement in 1RM with 67 the 'Slingshot' would be due to either A) an increased normalised sEMG 68 amplitude of the prime movers during or after the stick-period of the bench-69 press or B) that the improvement would be due to a greater peak and average 70 A C C E P T E D Copyright ª 2017 National Strength and Conditioning Association velocity in the early phases of the bench press as a result of the elastic assistance 71 provided by the 'Slingshot'. As a secondary hypothesis we also theorized that the 72 'Slingshot' would maintain barbell velocity during sets with multiple repetitions. The study consisted of two laboratory based trials of ~1.5hours each. Trials were 102 scheduled between 7<14 days apart and were completed at the same time of day 103 to account for circadian variation (4). During each trial, participants' 1RM bench 104 press was measured, followed by a predicted 3RM (3Rep) at 87.5% of achieved 105 1RM and 3 sub-maximal sets of 8 repetitions (8Rep) at 70% of achieved 1RM (2). 106 All participants completed the 'Raw' trial first (without the use of the Slingshot), 107 followed by the 'Slingshot' (SS) trial. 108 All bench press attempts were completed on a solid leather competition height 109 bench secured in position inside a FT700 Power Cage (Fitness Technology, 110 Australia), and using an IPF specification Eleiko PL competition barbell (Eleiko,111 Sweden), Eleiko WL coloured training discs (Eleiko, Sweden), and Eleiko 112 Olympic WL competition collars (Eleiko, Sweden). 113 Prior to commencing the initial trial, participants were provided with a 3-day 114 training and food diary, and asked to complete both diaries in the 2 days leading 115 up to, and day of testing. Participants were advised to maintain their normal diet along with a competition-style bench press 1RM (kg) predicted to the best of 123 their ability. Participants were also allowed to select their preferred rack height, 124 and demonstrated their bench press grip width, which was measured and 125 recorded (cm) and marked for reference on the barbell using masking tape. 126 Prior to commencing any warm-up activities, participants were familiarised with 127 the testing protocol and requirements, and allowed to ask any questions or for 128 any further information if required. During the initial phase of the warm-up, all 129 participants were required to familiarise themselves with the sEMG 130 normalisation procedure by completing controlled and consistent bench press 131 repetitions using the empty barbell to a metronome set at 30bpm, prior to 132 loading. During this familiarisation, a clearly audible metronome was played 133 through a pair of speakers, and participants were required to complete a full 134 competition style set up, un-rack the barbell, and perform as many repetitions as  All statistical analyses were carried out in GraphPad, Prism (GraphPad Software, 242 CA). Where 2 groups were compared, a 2 tailed t-test was performed. Where 243 more than two groups were compared, a 1 way ANOVA was utilized with a 244 Tukey's HSD test. Where multiple comparisons were made across groups, a 2 245 way ANOVA was performed with a Bonforoni's multiple comparisons test. 246 Normality of data was tested using D'Agostinio-Pearson omnibus normality test. 247 Where data were not normally distributed then the non-parametric two tailed t-248 tests were performed. When multiple comparisons were made on non-normal 249 data then a Friedman test was utilized with a Dunn's multiple comparisons test. 250 All data were reported as mean ± SEM and significance was set as a p value of p 251 ≤ 0.05. Correlations were determined via a simple linear regression. The displacement data demonstrates that there was no effect of wearing the 295 'Slingshot' on total displacement indicating that hand position was replicated 296 accurately between trials and that the 'Slingshot' did not affect the range of 297 motion ( Figure 6C). However, the 'Slingshot' significantly altered the 298 displacement at which the stick point occurred ( Figure 6C). The effect was small, 299 ~1cm higher in the concentric phase, but very consistent with 12 out of 15 300 subjects demonstrating an upward shift in the start of the stick point ( Figure 6C  Components of the velocity data from our study are somewhat reminiscent of the 345 velocity data obtained from performing the bench press with chain weight (6). At 346 the beginning of the concentric phase, the assistance from the device will likely 347 be greatest, and like with chains, the force required to move the bar off the chest 348 will be lower with the weight experienced increasing into lockout. Therefore, 349 increased velocity is an attractive theory for the mechanism of how the Aside from suggesting how the 'Slingshot' works, our data also suggest some 407 potential uses for the device in training. Some researchers have theorized that 408 the benefit of elastic training is that it allows for similar forces to be produced 409 but at faster velocities (20). The 'Slingshot' could be used as a speed training 410 device, as our data clearly demonstrate that velocity is substantially improved 411 whilst wearing the 'Slingshot'. Therefore, it may have some utility in velocity 412 training for sports such as the shot-put. However, the sEMG data shows that the 413 triceps are very likely de-loaded at all intensities with the 'Slingshot'. These 414 findings combined with the velocity data from the multiple repetition sets 415 suggest that the 'Slingshot' likely reduces fatigue and could also be used as a de-416 loading tool. One advantage of the 'Slingshot' over other de-loading or speed 417 training tools, such as using bands and chains, is its ease of use. Furthermore, 418 unlike other commonly used de-loading tools, the 'Slingshot' allows for a full 419 range of motion to be performed as demonstrated by total barbell displacement 420 during both 'Raw' and 'SS' trials. It should be noted that if the 'Slingshot' was 421 employed for a bulk of training, that the potential de-loading of the triceps would 422 A C C E P T E D very likely lead to a reduced performance on the bench press therefore it should 423 be used strategically and as a supplement to traditional bench press training. 424 In summary, the acute increases observed in bench press performance resultant 425 of using the 'Slingshot' suggest that it may be an effective training device for 426 speed training and de-loading the bench press exercise during a variety of 427 intensities whilst maintaining the full range of motion of the traditional format of 428 the bench press.

Acknowledgements
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. We gratefully acknowledge expert technical assistance for Mr Chris Grigson. Finally we are indebted to the volunteers who gave theirt ime to this study. Figure2. Electrode placement and positioning of the 'Slingshot.' Participants were instructed to wear the 'Slingshot' with the crease centred at the elbow. Electrodes were placed as described in the methods to ensure that the 'Slingshot' did not disrupt the electrodes during bench pressing.
Figure3. Defining the phases of maximal bench press attempts. Figure 3 illustrates a representative trace of acceleration, velocity and displacement during a 1RM attempt. The beginning of the pre-stick period (phase 1) was identified as the point at which velocity was 0 m/s 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 post-stick period (phase 3) began when acceleration again crossed 0 m/s 2 . The post-stick period ended when velocity reached 0 m/s at the end of the concentric phase.
Figure4. The 'Slingshot' increases the bench press 1 repetition maximum in a manner correlated to body mass. Fifteen trained power-lifters underwent rep max testing on two occasions separated by 7-14 days. The 'Raw' repetition maximum (1RM) was determined without any assistance and the SS repetition maximum was determined whilst wearing the 'Slingshot.' After the 1RM testing, 3 repetitions (3Rep) were A C C E P T E D 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 in (A). The absolute gain from wearing the 'Slingshot' (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). *indicates 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.
Figure5. The 'Slingshot' reduces 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 whilst wearing the 'Slingshot'. Surface EMG (sEMG) amplitudes were recorded during all sets and reps as described in the methods. All data presented are root mean squared (RMS) processed and normalised to the 70% normalisation set. A) 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 indicates 'Raw' is significantly different from both 'Raw max/SS' and 'SS' (as assessed by multiple comparisions). α indicates significantly different from 'SS' (as assessed by multiple comparisons). § indicates significantly different from 'Raw' (as assessed by multiple comparisons). * indicates 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.
Figure6. The 'Slingshot' 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 indicates 'Raw' is significantly different from both 'Raw max/SS' and 'SS.' α indicates significantly different from 'SS' (assessed by multiple comparisons). ε indicates significant difference between two bars (assessed by multiple comparisons). * indicates significantly different from 'Raw' (assessed by paired t-test) . Significance was determined as p≤0.05.

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Figure7. The 'Slingshot' reduces sEMG amplitude of the triceps brachii during a maximal effort. Surface EMG (sEMG) amplitudes were recorded during repetition maximum testing as described in the methods. All data presented are root mean squared (RMS) processed and normalised to the 70% normalisation set. A) sEMG amplitudes of the triceps brachii, B) sEMG amplitudes of the pectoralis clavicularus and C) sEMG amplitudes of the anterior deltoids. α indicates significantly different from 'SS' (as assessed by multiple comparisons p≤0.05).