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The relationship between lumbar spine load and muscle activity during extensor exercises
J P Callaghan1, J L Gunning, S M McGill
1Department of Kinesiology, University of Waterloo, Ontario, Canada.
Physical Therapy
|January 27, 1998
Summary
Trunk extension exercises vary in spine loading and muscle activity. Leg extension exercises with isometric trunk hold minimize spine load, while active trunk extensions create the highest loads.
Area of Science:
- Biomechanics
- Exercise Physiology
- Spinal Loading
Background:
- Quantitative assessment of spinal load during extensor exercises is lacking.
- Understanding trunk muscle activation is crucial for exercise prescription.
Purpose of the Study:
- To investigate lumbar spine loading during various trunk extensor exercises.
- To quantify trunk muscle activity levels during these exercises.
Main Methods:
- Thirteen male volunteers performed four different back exercises.
- Electromyography (EMG) recorded activity from 14 trunk muscles.
- Rigid body and EMG-driven models quantified L4-L5 joint loading.
Main Results:
- Active trunk extension exercises yielded the highest joint forces and muscle activity.
- Leg extension exercises with isometric trunk hold showed reduced spine loads due to asymmetrical muscle activity.
Conclusions:
- Back extensor exercises present a spectrum of spine loading and muscle activation.
- Single-leg extensions offer low spine load and mild muscle challenge for initial strengthening.
- Trunk extension exercises result in the highest compressive loading and extensor muscle activity.