Comparison of Myoelectric Activity During a Suspension-Based and Traditional Split Squat

Comparison of the Electromyography Activity during Exercises with Stable and Unstable Surfaces: A Systematic Review and Meta-Analysis

The effect of electromyographic (EMG) activity on agonist muscles during exercises performed on stable and unstable surfaces remains uncertain. We aimed to review the literature regarding the comparison of the EMG activity of the agonist muscles of exercises performed on stable and unstable surfaces. Eighty-six studies that evaluated the EMG activity of 1783 individuals during exercises for the lower limbs, upper limbs, and core were included. The EMG activities of the pectoralis major (SMD = 0.28 [95% CI 0.09, 0.47]) and triceps brachii muscles (SMD = 0.45 [95% CI 0.25, 0.66]) were significantly increased when the unstable device was added to the exercise. Likewise, the EMG activity of all core muscles showed a significant increase with the unstable surface during the exercises, such as the rectus abdominis (SMD = 0.51 [95% CI 0.37, 0.66]), external oblique (SMD = 0.44 [95% CI 0.28, 0.61]), internal oblique (SMD = 1.04 [95% CI 0.02, 2.07]), erector spinae (SMD = 0.37 [95% CI 0.04, 0.71]), and lumbar multifidus (SMD = 0.35 [95% CI 0.08, 0.61]). However, the lower limb muscles did not show greater EMG activity during the exercise with unstable surfaces compared to the stable surface. In conclusion, unstable conditions increase the EMG activity of some upper limb and core muscles compared to a stable surface.

Effects on Strength, Power and Speed Execution Using Exercise Balls, Semi-Sphere Balance Balls and Suspension Training Devices: A Systematic Review

Research in instability has focused on the analysis of muscle activation. The aim of this systematic review was to analyse the effects of unstable devices on speed, strength and muscle power measurements administered in the form of controlled trials to healthy individuals in adulthood. A computerized systematic literature search was performed through electronic databases. According to the criteria for preparing systematic reviews PRISMA, nine studies met the inclusion criteria. The quality of the selected studies was evaluated using STROBE. The average score was 14.3 points, and the highest scores were located in ‘Introduction’ (100%) and ‘Discussion’ (80%). There is great heterogeneity in terms of performance variables. However, instability seems to affect these variables negatively. The strength variable was affected to a greater degree, but with intensities near to the 1RM, no differences are observed. As for power, a greater number of repetitions seems to benefit the production of this variable in instability in the upper limb. Instability, in comparison to a stable condition, decreases the parameters of strength, power, and muscular speed in adults. The differences shown are quite significant in most situations although slight decreases can be seen in certain situations.

Kinematic and EMG Comparison Between Variations of Unilateral Squats Under Different Stabilities

The purpose of the study was to compare kinematics and muscle activity between two variations of unilateral squats under different stability conditions. Twelve male volunteers (age: 23±5 years, mass: 80±17 kg, height: 1.81±0.11 m, strength-training experience: 4.3±1.9 years) performed four repetitions with the same external load (≈4RM). Two variations (with the non-stance leg forwards vs. backwards) were performed in a Smith-machine and free-weight condition. The variables were barbell velocity, lifting time and surface electromyography activity of the lower extremity and trunk muscles during the descending and ascending phase. The main findings were 1) peak force was higher when performing the unilateral squats in the Smith machine; 2) peak ascending barbell velocity increased from repetition 3-4 with free weight; and 3) muscle activity from the rectus femoris, vastus lateral, biceps femoris, gluteus medius, and erector spinae increased with repetitions, whereas gluteus, and medial vastus and shank muscles were affected by the conditions. It was concluded that more peak force could be produced because of increased stability. However, peak barbell velocity increased from repetition to repetition in free-weight unilateral squats, which was probably because the participants grew more comfortable. Furthermore, increased instability causes more gluteus and vastus medial activation and foot variations mainly affected the calf muscles.