Trunk Training Exercises
Abstract & Commentary
Synopsis: Trunk flexion exercises are more effective than trunk extension exercises.
Source: Konrad P, et al. Neuromuscular evaluation of trunk-training exercises. Journal of Athletic Training. 2001;36(2): 109-118.
Konrad and colleagues examined activation of the trunk flexor and extensor muscles during 12 exercises using surface electromyography in 10 healthy subjects. Twelve trunk training exercises were performed in randomized order, including 5 for trunk and hip flexion, 2 for trunk lateral flexion, and 5 for trunk and hip extension.
The trunk flexion exercises while supine included: a straight curl-up (fingertips touch the temples, arms held in a fixed lateral position, head and shoulders lifted from 0-30° flexion, hip and knees at 90° flexion with legs supported and feet not fixed); a cross curl-up (same as straight curl-up except 1 leg across the other, one foot on the floor and contralateral elbow is moved to opposite knee); a hyperextended curl-up (same as straight curl-up with support placing low back in -20° extension and trunk flexion to 90° with feet not fixed); a sit-up (same as straight curl-up except knees at 90° flexion, feet not fixed on the floor, and flexion from 0-90°); and a vertical hip lift (knees flexed between 70-90°, arms fixed overhead, hip lifted until lumbar spine is lifted from the floor).
The lateral flexion exercises included lateral flexion with fixed legs while side-lying (foot of upper crossed over lower leg and fixed with lateral flexion until trunk is lifted from the floor to 30°) and a lateral hip lift (leaning on flexed elbow, hips elevated from the floor to neutral position).
The trunk extension exercises included: diagonal hip and shoulder extension (from quadrupled position, contralateral hip extension and shoulder flexion to horizontal position); kneeling back extension (from flexed chest-leg contact position, isolated back extension from 0-35°); trunk extension with fixed legs (prone with lower extremity to hips fixed and trunk lowered from 0-90° flexion); bridging (from supine position, trunk and arms resting on floor and knees flexed to 90°, hip extended to neutral position); and hip extension with fixed trunk (fixed upper body on table in prone position, from 90° hip and knee flexion with extension of legs to horizontal position).
Each subject performed 12 different static maximal voluntary contractions (MVC) from which %MVC was determined for each of the trunk training exercises. The muscles assessed included the trapezius (pars transversus), erector spinae (thoracic and lumbar parts), gluteus maximus, semitendinosus, semimembranosus, rectus abdominis, obliquus externus abdominis, and rectus femoris.
Konrad et al found good isolation of the abdominal muscles with the pure trunk flexion exercises, and that the EMG activity increased slightly with additional prestretch or rotation. High activation of the external oblique occurred with the lateral flexion exercises. The double supported back extension exercises (eg, diagonal hip and shoulder extension and bridging) elicited only moderate activity in the extensor muscles. The erector-spinae muscle activity was more effectively increased during prone-lying upper body vs. lower body movements.
Comment by David H. Perrin, PhD, ATC
The trunk provides the core from which many physically demanding movements originate. For this reason, adequate strength of the trunk musculature is essential for optimal performance. Additionally, well-balanced strength of the trunk extensor and flexor muscles is important for proper posture and prevention of back pain and dysfunction. Konrad et al confirmed the effectiveness of pure trunk flexion exercises for activation of the abdominal muscles. However, the trunk extension exercises produced comparatively low-mean EMG activity, with load and activation levels that may be insufficient to produce a training stimulus.
Athletes tend to devote considerable emphasis to training of the abdominal musculature, often in the complete absence of strengthening exercises for the trunk extensors. This training strategy can lead to muscle imbalances between these agonist and antagonist muscles. Proper supervision of training and rehabilitation programs is essential to ensure that strengthening exercises are applied to all trunk and upper and lower extremity agonist and antagonist muscle groups.
The finding that these commonly used trunk extension exercises produced only moderate EMG activity of the erector spinae muscles is troublesome. Further research is needed to devise and validate additional exercises for strengthening and rehabilitation of the trunk extensor musculature.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content