Abstract
This study investigated the trunk kinematics and electromyographic (EMG) activity of eight trunk muscles when 'expected' and 'unexpected' loads were applied directly to the torso. Twenty individuals (mean age: 25.1yr; range 20-33yr) participated in this mixed model study in which gender was the between-subjects factor, and expectancy and symmetry of the applied load were within-subject factors. The sudden load was delivered to the subject via a cable attached to a thoracic harness and motion was restricted to the lumbar spine by strapping the pelvis to a rigid fixation apparatus. Surface EMG was recorded bilaterally from the longissimus thoracis (LGT), erector spinae (ERS), rectus abdominis (RAB) and the external obliques (EXO). Trunk kinematics were measured with a Lumbar Motion Monitor(TM). During expected loading conditions, the peak muscle activity was reduced for the RAB and EXO bilaterally, and for the ERS(R) (p<0.01) relative to the unexpected conditions. Conversely, the normalized area of EMG activity prior to the onset of load was increased for the ERS and EXO bilaterally, and for the RAB(R) (p<0.05) during an expected loading event. Trunk motion in the sagittal and frontal planes was reduced during expected loading. Activation of the trunk muscles just prior to a rapid loading event increases trunk stiffness, decreasing trunk displacement and peak muscle activity. Copyright (C) 1998 Elsevier Science Ltd.
Original language | English (US) |
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Pages (from-to) | 215-225 |
Number of pages | 11 |
Journal | Journal of Electromyography and Kinesiology |
Volume | 8 |
Issue number | 4 |
DOIs | |
State | Published - Aug 1998 |
Funding
This study was supported in part by grants from the National Institute for Occupational Safety and Health (USPHS R03 OH0333-02), the National Institute of Neurological and Communicative Disorders and Stroke (K4-NS 01508 and RO1-NS 28127) and the National Institute of Arthritis and Musculoskeletal and Skin Diseases (RO1-AR 33189). The experiments were performed in partial fulfillment of a Master's Degree (J.S.T) at the University of Illinois at Chicago. We would also like to acknowledge the invaluable advice of Dr Ziaul Hasan on many aspects of this project.
Keywords
- Biomechanics
- Gender
- Spine
- Sudden loading
- Trunk muscle activity
ASJC Scopus subject areas
- Neuroscience (miscellaneous)
- Biophysics
- Clinical Neurology