ABSTRACT
The aim of this review was to systematically explore the underlying musculoskeletal biomechanical mechanisms of carrying and to describe its potential relationship with low back pain. This literature review was carried out using AMED, CINAHL, Compendex and MEDLINE electronic databases. Articles published from 2004 to 2012 were selected for consideration. Articles were considered if at least one measurement of kinetics, kinematics or other related musculoskeletal parameters related to biomechanics were included within the study. After combining the main keywords, 677 papers were identified. However, only 10 studies met all the inclusion criteria. Age, body mass index, gender and level of physical activity were identified as the factors that may influence the biomechanics of carrying activity. Carrying a loaded backpack was reported leading to posterior pelvic tilt, reduced lumbar lordosis, but increased cervical lordosis, thoracic kyphosis and trunk forward lean. Furthermore, while carrying bilaterally, lumbo-pelvic coordination was also reported to be more in-phase, as well as reduced coordination variability in transverse plane. Future studies investigating the biomechanics of a standardized carrying activity for clinical test are recommended.
Subject(s)
Low Back PainABSTRACT
Objective To observe the activation patterns in surface electromyographs (sEMGs) of the lumbar dorsal and ventral muscles and the gluteus medius during asymmetrical trunk postures and while carrying loads with the trunk rotated.Methods sEMGs were recorded from ten healthy men as they stood with their feet in 5 positions-rotated clockwise 0°,45°,90°,135° and 180° with respect to the initial plane of the torso.With each foot position they stood in 3 postures:upright,in lateral flexion and in lateral extension.Each posture was recorded with and without carrying a load of 20 kg by the right hand.The EMG activities of the rectus abdominis (RA),obliquus externus abdominis (EO),erector spinae (ES),multifidus (LM) and gluteus medius (GM) on both sides were recorded.Trunk displacement was monitored by 8 cameras.The EMG data of each muscle were normalized with readings from a maximal voluntary contraction (MVC) of the muscle.Results With the feet at 0° and no load the muscle activities on both sides were 1％-2％ of the MVC readings.With a 20 kg load the percentage was 3％-13％.With the feet at 45° and no load the activities were greater,except in the RA on the contralateral side.With no load at 90°,135° and 180° the muscle activities were greater,but a few muscles in the two extreme trunk postures showed greater activity only on one side,especially the ES and LM.With a load and rotational torque in the spine,the ventral muscles were less active but the dorsal muscles were significantly more active on both sides.Conclusion Standing with rotation of the spine,the activity of some trunk muscles shows great asymmetry,particularly with asymmetric loading of the arms.This might create a phenomenon of lumbar flashing and it could possibly be one of the pathological bases of acute lumbar sprain.
ABSTRACT
OBJECTIVES: Load carrying tasks are recognized as one of the primary occupational factors leading to slip and fall injuries. Nevertheless, the mechanisms associated with load carrying and walking stability remain illusive. The objective of the current study was to apply local dynamic stability measure in walking while carrying a load, and to investigate the possible adaptive gait stability changes. METHODS: Current study involved 25 young adults in a biomechanics research laboratory. One tri-axial accelerometer was used to measure three-dimensional low back acceleration during continuous treadmill walking. Local dynamic stability was quantified by the maximum Lyapunov exponent (maxLE) from a nonlinear dynamics approach. RESULTS: Long term maxLE was found to be significant higher under load condition than no-load condition in all three reference axes, indicating the declined local dynamic stability associated with load carrying. CONCLUSION: Current study confirmed the sensitivity of local dynamic stability measure in load carrying situation. It was concluded that load carrying tasks were associated with declined local dynamic stability, which may result in increased risk of fall accident. This finding has implications in preventing fall accidents associated with occupational load carrying.
Subject(s)
Humans , Young Adult , Acceleration , Biomechanical Phenomena , Gait , Lifting , Nonlinear Dynamics , WalkingABSTRACT
PURPOSE: To clarify the behavior of the lumbar spine under vertical compressive load and follower compressive load and to confirm the effect of the follower load on the stability of the spinal column using finite element method. MATERIALS AND METHODS: Describing follower compression test to overcome underestimation of load carrying capacity, the problem in existing ex-vivo lumbar spine compression test, with finite element analysis, comparing with the result of simple vertical compressive load, we analyze the property of kinetic behavior. After performing finite element modelling about L1-L5 lumbar vertebral column, analyze it about vertical compressive load and follower compressive load. Intervertebral discs with complex structure and mechanical properties was modeled using spring element that compensate stiffness and tube-to-tube contact element was employed to give follower load. With compressive load, change of lumbar spinal curve is so much, that geometrical analysis should be done. RESULTS: Under the follower compressive load, the vertebral column was so stiff that vertical displacement of the upper end plate of L1 was markedly reduced, comparing with that under the simple vertical compressive load. Sagittal rotation of that upper end plate was also decreased in the opposite direction. Compressive load on the intervertebral disc was evenly distributed along the entire column. The bending moment at each disc was reduced in the opposite direction. A lesser A-P shear force occurred at the intervertebral disc. CONCLUSION: As a result of finite element interpretation of lumbar spine, the stability and load carrying capacity was increased largely, and the compressive load was transmitted through the column in a more pattern, when follower compressive load applied. This can provide the basis for explaining the difference of early buckling occurrence reported in ex-vivo testing, and load carrying capacity of the lumbar spine in-vivo, but, for more precise replication of behavior of lumbar spine in-vivo to variable loading. A invention of a more precious finite element interpretation model which consider the role of muscle around the spine is loaded.