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Frequency-dependent changes in neuromuscular responses to cyclic lumbar flexion
Dawei Lu1, Moshe Solomonow, B Zhou
1Department of Orthopaedic Surgery, Louisiana State University, Suite 400, 2025 Gravier Street, New Orleans, LA 70112, USA.
Journal of Biomechanics
|April 28, 2004
Summary
Higher repetition rates in repetitive lifting increase the risk of low back disorders. Faster cyclic loading intensifies neuromuscular issues and tissue creep, confirming frequency as a significant risk factor.
Area of Science:
- Biomedical Engineering
- Occupational Health
- Musculoskeletal Research
Background:
- Repetitive lifting is a known cause of low back disorders.
- Epidemiological data suggests higher lifting frequencies exacerbate risk.
Purpose of the Study:
- To experimentally test the hypothesis that higher repetition rates increase low back disorder risk.
- To investigate the effects of cyclic lumbar loading frequency on neuromuscular responses and tissue creep.
Main Methods:
- An in vivo feline model was used for cyclic lumbar loading at 0.1 Hz and 0.5 Hz for 20 minutes.
- Electromyography (EMG) of multifidus muscles and lumbar creep at L-4/5 were monitored.
- Recovery was assessed for 7 hours post-loading with hourly test cycles.
Main Results:
- Cyclic lumbar flexion induced transient neuromuscular disorders, including EMG spasms and muscular hyperexcitabilities.
- Loading at 0.5 Hz significantly increased the magnitude and duration of hyperexcitability during recovery (p<0.05).
- Faster loading rates led to greater lumbar tissue creep.
Conclusions:
- Repetitive lumbar loading at higher frequencies is a significant risk factor for low back disorders.
- Increased tissue creep at faster rates intensifies the resulting neuromuscular disorder.
- Findings support the hypothesis linking lifting frequency to increased risk and severity of low back issues.