Volume 13, Issue 2 (6-2023)
J Health Saf Work 2023, 13(2): 202-217 |
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Kazemi Z, Mazloumi A, Arjmand N, Karimi Z, Keihani A, Ghasemi M S. The Effect of Repetitive Lifting on Trunk Muscles’ Fatigue and Kinematics of Spine and Load-in-Hand. J Health Saf Work 2023; 13 (2) :202-217
URL: http://jhsw.tums.ac.ir/article-1-6716-en.html
URL: http://jhsw.tums.ac.ir/article-1-6716-en.html
Zeinab Kazemi1 
, Adel Mazloumi * 2, Navid Arjmand3 , Zanyar Karimi4 , Ahmadreza Keihani5 , Mohammad Sadegh Ghasemi6
, Adel Mazloumi * 2, Navid Arjmand3 , Zanyar Karimi4 , Ahmadreza Keihani5 , Mohammad Sadegh Ghasemi6
1- Department of Industrial Engineering, Clemson University, Clemson, USA
2- Sports Medicine Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran | Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran ,amazlomi@tums.ac.ir
3- Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
4- Department of Ergonomics, School of Public Health, Urmia University of Medical Sciences, Tehran, Iran
5- Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
6- Department of Ergonomics, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
2- Sports Medicine Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran | Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran ,
3- Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
4- Department of Ergonomics, School of Public Health, Urmia University of Medical Sciences, Tehran, Iran
5- Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
6- Department of Ergonomics, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
Abstract: (884 Views)
Introduction: Given the high prevalence of low back pain in manual handling activities, its known relationship with spinal loads, and the role of muscular fatigue and the body’s adaptive mechanisms to counteract fatigue, this study investigated the effect of repetitive lifting tasks on trunk muscular fatigue and the kinematics of the spine and load-in-hand.
Material and Methods: Eighteen male volunteers lifted a box from the floor to their waist height at a pace of ten lifts per minute until they could no longer continue the task and reported the highest level of exhaustion. Kinematic data and muscle electromyographic activity were simultaneously recorded using a motion capture system and an electromyography device. In this study, average trunk flexion angle and trunk angular velocity were calculated as trunk kinematic variables, while average box vertical travel distance, average box horizontal displacement from L5-S1, and average box vertical displacement velocity were considered as box kinematic variables. The median frequency of electromyographic signals from selected muscles was quantified as a muscle fatigue indicator. Since subjects performed different lifting cycles, the total number of cycles was divided into five distinct blocks for data analysis.
Results: The results showed significant effects of lifting trial blocks on trunk angle (p=0.004) and vertical box displacement (p<0.001). Median frequency was significantly affected by lifting blocks for right (p=0.016) and left erector spinae (p=0.014), right (p=0.021) and left multifidus (p<0.001), right latissimus dorsi (p=0.001), and left rectus abdominis (p=0.039).
Conclusion: Overall, the results highlight variations in most kinematic parameters and a reduction in the frequency content of EMG signal spectra. These changes serve as indices of the central nervous system’s control over lifting behavior under dynamic conditions. A better understanding of these central nervous system adaptations could have practical applications in interventions such as workstation design, exoskeleton development, and worker training to manage musculoskeletal disorders.
Material and Methods: Eighteen male volunteers lifted a box from the floor to their waist height at a pace of ten lifts per minute until they could no longer continue the task and reported the highest level of exhaustion. Kinematic data and muscle electromyographic activity were simultaneously recorded using a motion capture system and an electromyography device. In this study, average trunk flexion angle and trunk angular velocity were calculated as trunk kinematic variables, while average box vertical travel distance, average box horizontal displacement from L5-S1, and average box vertical displacement velocity were considered as box kinematic variables. The median frequency of electromyographic signals from selected muscles was quantified as a muscle fatigue indicator. Since subjects performed different lifting cycles, the total number of cycles was divided into five distinct blocks for data analysis.
Results: The results showed significant effects of lifting trial blocks on trunk angle (p=0.004) and vertical box displacement (p<0.001). Median frequency was significantly affected by lifting blocks for right (p=0.016) and left erector spinae (p=0.014), right (p=0.021) and left multifidus (p<0.001), right latissimus dorsi (p=0.001), and left rectus abdominis (p=0.039).
Conclusion: Overall, the results highlight variations in most kinematic parameters and a reduction in the frequency content of EMG signal spectra. These changes serve as indices of the central nervous system’s control over lifting behavior under dynamic conditions. A better understanding of these central nervous system adaptations could have practical applications in interventions such as workstation design, exoskeleton development, and worker training to manage musculoskeletal disorders.
Type of Study: Research |
Received: 2022/08/9 | Accepted: 2023/01/31 | Published: 2023/06/22
Received: 2022/08/9 | Accepted: 2023/01/31 | Published: 2023/06/22
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