A Comparison of Electromyographic Inter-Limb Asymmetry during a Standard versus a Sling Shot Assisted Bench Press Exercise

Abstract

The objective of this study was to compare peak surface electromyography (sEMG) activity of selected muscles along with inter-limb asymmetries between a control (CONT) and a Sling shot assisted (SS) bench press exercise. Ten resistance-trained males with at least three-year experience in resistance training (22.2 ± 1.9 years, 88.7 ± 11.2 kg, 179.5 ± 4.1 cm, bench press one-repetition maximum (1RM) = 127.3 ± 25.9 kg) performed the flat bench press exercise under two conditions at selected loads (85% and 100% of 1RM assessed without the SS). Peak sEMG amplitude of triceps brachii, pectoralis major, and anterior deltoid was recorded for the dominant and the non-dominant side of the body during each attempt. The comparison between the dominant and the non-dominant side was carried out using the limb symmetry index (LSI(%) = (2*(XR - XL)/(XR + XL))*100%) where XR = values of the right side and XL = values of the left side. There was a main effect of condition (p = 0.004; η2 = 0.64) and the load (p = 0.004; η2 = 0.63) for the triceps brachii LSI in parallel with a main effect of condition (p = 0.003; η2 = 0.42) for the anterior deltoid LSI. Post hoc analysis for the main effect of condition showed significant differences in the LSI between the CONT and SS conditions for the triceps brachii (p = 0.003; 1.10% vs. -8.78%) as well as for the anterior deltoid muscles (p = 0.03; 12.91% vs. 9.23%). The results indicate that the assistance of the Sling shot significantly affects the sEMG activity pattern on both the dominant and non-dominant sides of the body while influencing inter-limb asymmetries.

The Effects of the “Sling Shot” Device on Bench Press Performance, Mechanical Properties of Muscle, and Movement Kinematics

“…On the contrary, previous studies that included the measurement of muscle activity by sEMG and the use of the SS showed a significant difference between the conditions, body sides, and applied external loads (6,36,38). The authors have shown that the use of the SS acutely reduces muscle activity, which, however, increases with increasing load, and that there are also significant differences in activity between the upper limbs (37). It also seems that the SS support increases the relative involvement of the nondominant limb while decreasing the sEMG muscle activity of both limbs (37).…”

“…The authors have shown that the use of the SS acutely reduces muscle activity, which, however, increases with increasing load, and that there are also significant differences in activity between the upper limbs (37). It also seems that the SS support increases the relative involvement of the nondominant limb while decreasing the sEMG muscle activity of both limbs (37). Similarly, in this study, the dominant limb triceps brachii long head stiffness was significantly higher than that in the nondominant limb in the CONT condition, with no such differences in the SS condition.…”

“…Then, the subjects practiced the bench press as well as the SS-assisted bench press repeatedly until they felt comfortable performing the exercise (36,38). At last, the subjects performed 3–5 sets of a single bench press repetition with the SS using 80% 1RM to ensure technical proficiency (37).…”

“…The SS is made of 2 resilient sleeves wrapping around the elbows connected with extensible material. The stretching of the material that makes up the SS provides additional elastic energy that supports the athlete in the eccentric phase of the movement and allows for a rebound effect in the concentric phase of the lift (36,37). Research has shown that SS affects BP performance variables, increasing results of the one repetition maximum test (1RM), the generated power and bar velocity, and the number of repetitions performed until muscular failure.…”

“…Research has shown that SS affects BP performance variables, increasing results of the one repetition maximum test (1RM), the generated power and bar velocity, and the number of repetitions performed until muscular failure. The use of the SS also changes the surface electromyography readings (sEMG), thus changing the activity pattern of the prime movers depending on the applied external load (6,26,27,(36)(37)(38).…”