title: Deep and superficial abdominal muscle activation during trunk stabilization exercises with and without instruction to hollow.
abstract: The deepest muscle of the human ventro-lateral abdominal wall, the Transversus Abdominis (TrA), has been ascribed a specific role in spine stabilization, which has motivated special core stability exercises and hollowing instruction to specifically involve this muscle. The purpose here was to evaluate the levels of activation of the TrA and the superficial Rectus Abdominis (RA) muscles during five common stabilization exercises performed in supine, bridging and four-point kneeling positions, with and without instruction to hollow, i.e. to continuously pull the lower part of the abdomen towards the spine. Nine habitually active women participated and muscle activity was recorded bilaterally from TrA and RA with intramuscular fine-wire electrodes introduced under the guidance of ultrasound. Results showed that subjects were able to selectively increase the activation of the TrA, isolated from the RA, with the specific instruction to hollow and that side differences in the amplitude of TrA activity, related to the asymmetry of the exercises, remained even after the instruction to hollow. The exercises investigated caused levels of TrA activation from 4 to 43% of that during maximal effort and can thus be used clinically to grade the load on the TrA when designing programs aiming at training that muscle.
authors.affiliation: The Swedish School of Sport and Health Sciences (GIH), Biomechanics and Motor Control Laboratory, Box 5626, SE-114 86 Stockholm, Sweden. anna.bjerkefors@gih.se
authors.forename: Anna
authors.initials: A
authors.lastname: Bjerkefors
authors.forename: Maria M
authors.initials: MM
authors.lastname: Ekblom
authors.forename: Karin
authors.initials: K
authors.lastname: Josefsson
authors.forename: Alf
authors.initials: A
authors.lastname: Thorstensson
mesh_terms: D000009:Abdominal Muscles / Q000502:physiology*; D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000517:prevention & control; D009119:Muscle Contraction / Q000502:physiology*; D011187:Posture / Q000502:physiology; D018084:Ultrasonography, Interventional