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Published on: December 14, 2011
Effects of eccentric exercise on trunk extensor torque and lumbar paraspinal EMG
1Human Performance Laboratory, Department of Health and Kinesiology, Texas A&M University, College Station, TX 77843, USA. hermannkarl@hotmail.com
Medicine and Science in Sports and Exercise
|June 19, 2001
Summary
Eccentric contractions increase multifidus muscle activity in the trunk extensors, reducing neuromuscular efficiency for up to one day. This effect on lumbar paraspinal muscles differs from other muscle groups, with function returning to baseline by day three.
Area of Science:
- Biomechanics
- Exercise Physiology
- Neuromuscular Function
Background:
- The effects of eccentric contractions on lumbar paraspinal muscle function are not well understood.
- Eccentric exercise involves muscle lengthening under load, differing from concentric (shortening) exercise.
Purpose of the Study:
- To investigate the impact of a single bout of eccentric contractions on trunk extensor torque and electromyographic (EMG) activity of lumbar paraspinal muscles.
- To compare these effects with concentric contractions.
Main Methods:
- Twenty healthy men (18-49 years) performed 50 maximal voluntary concentric or eccentric trunk extensions.
- Surface EMG was recorded from multifidus and iliocostalis lumborum.
- Isometric contractions were measured pre-exercise and for 7 days post-exercise.
Main Results:
- Peak torque decreased in both groups, but EMG root-mean-square (RMS) remained unchanged during exercise.
- The eccentric group showed significantly elevated multifidus EMG activity post-exercise (up to 1 day) compared to the concentric group.
- No significant group differences in peak torque were observed at post-exercise time points.
Conclusions:
- Eccentric trunk extensions lead to increased multifidus EMG for a given torque, indicating reduced neuromuscular efficiency.
- This effect persisted for one day, with recovery by day three.
- Unlike other muscle groups, no sustained alteration in lumbar paraspinal muscle function was observed.
