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

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.

Effects of Unilateral Lower-extremity Joint Cooling on Movement Biomechanics during Two-legged Jumping and Landing

OBJECTIVES This study examined the immediate effect of unilateral ankle or knee joint cooling on the low-erextremity kinematics and kinetics during two-legged jumping and landing.METHODS Twenty healthy adults randomly completed three data collection sessions for ankle or knee joint cooling, or control. For each session, participants performed two-legged countermovement jumps and lands. For joint cooling, two ice bags were directly placed to the right side and secured with a compression bandage. A three-dimensional motion analysis system (200 Hz) with two floor-embedded force platforms (2000 Hz) was employed to capture the jumping and landing. The cooling effects on kinematical (flight time, and sagittal plane joint angles) and kinetical (peak vertical ground reaction force (vGRF), impulse, and sagittal plane joint moments) variables were examined. A mixed-model analysis of variance was performed for each dependent variable (<i>p</i>≤0.0001 for all tests).RESULTS We did not observe any interactions (flight time: F_2,95=0.67, <i>p</i>=0.52; joint angles: F_2,209≤2.26, <i>p</i>≥0.10; peak vGRF: F_2,209≤1.76, <i>p</i>≥0.20; impulse: F_2,209≤2.54, <i>p</i>≥0.10; joint moments: F_2,209≤4.80, <i>p</i>≥0.01 for all interactions). Regardless of condition and time (side effect), subjects showed a dominant-leg predominant movement strategy. Specifically, the right side showed a greater peak vGRF (2%), and greater ankle (7%), knee (6%), and hip (11%) joint moments, as compared with the left side during jumping. The same movement pattern was observed during landing that there was greater peak vGRF (11%) and impulse (8%), and greater ankle and knee joint moments (15%). Regardless of time and side (condition effect), subjects with ankle joint cooling showed 5% lesser ankle joint moment during jumping, compared with those who received knee joint cooling (<i>p</i>=0.0001).CONCLUSIONS A 20-min of unilateral ankle or knee joint cooling seems to neither alter vertical jump height nor change movement biomechanics during two-legged jumping and landing.

A Narrative Review of Limb Dominance: Task Specificity and the Importance of Fitness Testing

ABSTRACT

Virgile, A and Bishop, C. A narrative review of limb dominance: Task specificity and the importance of fitness testing. J Strength Cond Res 35(3): 846-858, 2021-Preferential limb function must be sustained through repetitious asymmetrical activities for continuous athletic development and, ultimately, optimal athletic performance. As such, the prevalence of limb dominance and between-limb differences is common in athletes. Severe between-limb differences have been associated with reductions in athletic performance and increased injury risk in athletes. However, in the current literature, the terms limb preference and limb dominance have been used interchangeably. Together, these terms include a limb that is subjectively preferred and one that is objectively dominant in 1 or more performance measures from a variety of athletic tasks. In this review, we (a) discuss reported correspondence between task-specific limb preference and limb dominance outcomes in athletes, (b) provide greater context and distinction between the terms limb preference and limb dominance, and (c) offer pragmatic strategies for practitioners to assess context-specific limb dominance. A limb that is subjectively preferred is not necessarily objectively dominant in 1 or more athletic qualities or sport-specific tasks. Further to this, a limb that is objectively superior in 1 task may not exhibit such superiority in a separate task. Thus, limb preference and limb dominance are both task-specific. As such, we propose that practitioners intentionally select tasks for limb dominance assessment which resemble the most relevant demands of sport. Because limb dominance profiles are inconsistent, we suggest that practitioners increase assessment frequency by integrating limb dominance testing into standard training activities. This will allow practitioners to better understand when changes reflect sport-specific adaptation vs. potential performance or injury ramifications.