Article

Transversus abdominis (TrA) is a multifunctional muscle, being involved in
pressure regulation within the abdominal cavity and thereby in direction
independent stabilization of the spine and resistance to imposed trunk flexion
moments. Indirect evidence suggests a role of TrA also in postural control of the
erect human trunk. The main purpose here was to investigate if the magnitude of
TrA activation is related to postural demand. Eleven healthy males performed
seven different symmetrical static bilateral arm positions holding 3 kg in each
hand. The arm positions were selected to systematically vary the height of the
centre of mass (COM) keeping imposed moments constant and vice versa. EMG was
recorded bilaterally with fine-wire intramuscular electrodes from TrA and
obliquus internus (OI) and with surface electrodes from rectus abdominis (RA) and
erector spinae (ES). Intra-abdominal pressure (IAP) was measured via a pressure
transducer in the gastric ventricle. TrA was the only muscle that displayed
activation co-varying with the vertical position of the COM. Further, TrA
activation increased, together with IAP and ES activation, with imposed flexion
moment, i.e. with arms extended horizontally forward. In contrast to OI, RA and
ES, TrA activation was independent of the direction of the imposed moment (arms
held inclined forward or backward). In conclusion, TrA activation level is
uniquely associated with increased postural demand caused by elevated COM. Also,
TrA appears to assist in counteracting trunk flexion via increased IAP, and
contribute to general spine stabilization when the trunk is exposed to moderate
flexion and extension moments.
CI - Copyright (c) 2011 Elsevier B.V. All rights reserved.

Langue : ANGLAIS