Activity Pattern of the Erector Spinae Muscles During Two Lumbar Strengthening Exercises
The flexion-relaxation-phenomenon is the specific response of the erector spinae muscles, in free-pain subjects, during forward bending from upright standing. The contraction intensity of the erector spinae has been studied during trunk exercises on the roman chair, which has brought about significant information in order to graduate lumbar training intensity. To our knowledge, no study determined the pattern of erector spinae activity in the course of movement at the roman-chair exercises. The EMG of the right erector spinae and the angular displacement of the dorso-lumbar spine were symultaneously recorded during the time-course of flexion-extension exercises at upright standing and roman chair (n=20, M: 21.4 years, 64.5Kg and 168.4cm), the muscles activation were compared between the two exercises and different patterns were observed. The flexion-relaxation–phenomenon was observed during flexion form upright standing but not during exercises at the roman chair, the maximum amplitude of flexion was significantly less (p ≤ 0.05) and progresive decrease in ES activity occurred when the trunk flexed by maximum. Avoiding maximum range of flexion during trunk exercises is recommended since, as a rule during lumbar training, it may prevent from spine injury.
KEY WORDS: Erector spinae, flexion-relaxation phenomenon, roman-chair exercises, lumbar-strengthening-exercises, lumbar motion.