[Purpose] Although lifting tasks has been recognized as a primary risk factor in low back pain, the concept of lifting asymmetry is relatively new subject. To address trunk function, biomechanical studies generally measure trunk muscle activity using surface electromyography (EMG). But so far, magnitude and similarity index (SI) obtained from EMG have not been studied as indicators of the motor control during lifting task. So, the purpose of this study is to compare the trunk muscles magnitude and SI during symmetric and asymmetric lifting. [Subjects and Methods] A total of 20 healthy male with no history of lumbar spine disorders participated. Surface electromyography data were recorded from the 7 trunk muscles while the participants performed symmetric and asymmetric lifting and lowering different loads. [Results] According to Multivariate ANOVAs the phase of motion (lifting, lowering) and condition (symmetry, asymmetry) have a significant effect on SI and magnitude (p≤0.05). Load changes have no effect on SI (p=0.969) but have a significant effect on magnitude (p≤0.05). The magnitude and SI value is higher in asymmetrical lifting and lowering compare to symmetrical condition. [Conclusion] The findings reveal the SI value is higher in asymmetric conditions. This means that the amount of muscles co-contracture increased during asymmetrical conditions. Increased muscles co-contracture reinforces the hypothesis of exerting more compression on the spine in asymmetrical movement. Keywords: Asymmetrical lifting, Motor control, Electromyography
Background and Purpose: The beliefs are that sudden and unpredictable balance disturbance by instruments that cause mechanical perturbations can affect individuals with Anterior Cruciate Ligament Deficiency (ACLD) to reach faster and more effective recovery of knee dynamic stabilization strategies to return successfully pre-injury levels. The aim of this study was to investigate the effect of mechanical perturbation training and standard training in the process of changes in motor control during walking task in coper ACLD individuals. Methods: Thirty athletes with a unilateral rupture of the Anterior Cruciate Ligament (ACL), classified as coper, were randomly assigned to perturbation and standard training groups. Intervention training results based on comparison of scores obtained from functional tests in 4 single-leg jump tests, scores of questioners, and surface Electromyography (sEMG) tests were determined between the two groups as well as between the two healthy and ACLD limbs in each group in the walking task. Results: The perturbation training group showed a significant increase in muscle activity in both healthy and ACLD limbs with an increase in similarity index (SI) (p=0.08, ES=0.81), while in the standard training group the results were not significant (p=0.39, ES=0.39). Conclusion: Individuals in the perturbation training group achieved higher scores on all tests compared to the standard training group. This means that the perturbation training group was more mentally and physically prepared in terms of strength, coordination and symmetry between the two limbs to participate in pre-injury sports levels.
Introduction: Studies have repeatedly discussed the importance of training with sufficient cognitive and sensory-motor challenges in successfully transferring Anterior Cruciate Ligament Deficiencies (ACLDs) from rehabilitation centers to sports facilities. For this purpose, this study investigated the effect of mechanical perturbation training and standard training on the brain and muscle activity of these individuals while jumping on one leg. Materials and Methods: A total of 30 athletes with unilateral Anterior Cruciate Ligament (ACL) rupture (in the coper classification) were randomly assigned to perturbation and standard training groups. To compare the effect of two types of intervention training methods, we examined the Similarity Index (SI) and Voluntary Response Index (VRI) in surface Electromyography (sEMG) tests of eight muscles in the lower extremities and relative power of alpha and beta spectra in Quantitative Electroencephalographic (QEEG) tests between two groups and between two limbs of each group members in the single-leg jump task. Results: Both training groups showed improved neuromuscular control and increased SI on sEMG tests between the two limbs. However, this improvement in the perturbation training group showed an excellent increase in Effect Size (ES) (intra-group comparison values of SI for perturbation training group P=0.0001, ES=3.6; and P=0.008, ES=1.24 in the standard training group; and P=0.04, ES=0.87 in the inter-group comparison). Regarding the post-test of QEEG tests, no significant difference was found between the two groups (alpha P-value: 0.13, beta P-value: 0.07). However, in the intra-group comparison, the perturbation training group achieved excellent symmetry for the relative power spectrum of alpha and beta signals (the similarity values between the two limbs in the perturbation training group for alpha were P=0.92, ES=0.04 and for beta were P=0.92, ES=0.02; and these values for standard training group for alpha were P=0.07, ES=0.86 and for beta as P=0.08, ES=0.87). Conclusion: The present study results showed that mechanical perturbation and standard training are suitable for transporting ACLDs to sports environments. Furthermore, in comparing these two training methods, mechanical perturbation training in the manner used in this study has higher adequacy to eliminate motor control and central nervous system defects.
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