TY - JOUR
T1 - The sit-up
T2 - Complex kinematics and muscle activity in voluntary axial movement
AU - Cordo, P. J.
AU - Gurfinkel, V. S.
AU - Smith, T. C.
AU - Hodges, P. W.
AU - Verschueren, S. M.P.
AU - Brumagne, S.
N1 - Funding Information:
The authors gratefully acknowledge Graham Kerr, Ph.D. and Ron Jacobs, Ph.D. for their contributions to the development of the force table and to the National Institutes of Health for funding this project (AR31017, AR46007). S.V. was supported by the Fund for Scientific Research, Flanders, Belgium. S.B. was supported by the Research Council of the Katholieke Universiteit Leuven.
PY - 2003/6
Y1 - 2003/6
N2 - This paper describes the kinematics and muscle activity associated with the standard sit-up, as a first step in the investigation of complex motor coordination. Eight normal human subjects lay on a force table and performed at least 15 sit-ups, with the arms across the chest and the legs straight and unconstrained. Several subjects also performed sit-ups with an additional weight added to the head. Support surface forces were recorded to calculate the location of the center of pressure and center of gravity; conventional motion analysis was used to measure segmental positions; and surface EMG was recorded from eight muscles. While the sit-up consists of two serial components, 'trunk curling' and 'footward pelvic rotation', it can be further subdivided into five phases, based on the kinematics. Phases I and II comprise trunk curling. Phase I consists of neck and upper trunk flexion, and phase II consists of lumbar trunk lifting. Phase II corresponds to the point of peak muscle contraction and maximum postural instability, the 'critical point' of the sit-up. Phases III-V comprise footward pelvic rotation. Phase III begins with pelvic rotation towards the feet, phase IV with leg lowering, and phase V with contact between the legs and the support surface. The overall pattern of muscle activity was complex with times of EMG onset, peak activity, offset, and duration differing for different muscles. This complex pattern changed qualitatively from one phase to the next, suggesting that the roles of different muscles and, as a consequence, the overall form of coordination, change during the sit-up.
AB - This paper describes the kinematics and muscle activity associated with the standard sit-up, as a first step in the investigation of complex motor coordination. Eight normal human subjects lay on a force table and performed at least 15 sit-ups, with the arms across the chest and the legs straight and unconstrained. Several subjects also performed sit-ups with an additional weight added to the head. Support surface forces were recorded to calculate the location of the center of pressure and center of gravity; conventional motion analysis was used to measure segmental positions; and surface EMG was recorded from eight muscles. While the sit-up consists of two serial components, 'trunk curling' and 'footward pelvic rotation', it can be further subdivided into five phases, based on the kinematics. Phases I and II comprise trunk curling. Phase I consists of neck and upper trunk flexion, and phase II consists of lumbar trunk lifting. Phase II corresponds to the point of peak muscle contraction and maximum postural instability, the 'critical point' of the sit-up. Phases III-V comprise footward pelvic rotation. Phase III begins with pelvic rotation towards the feet, phase IV with leg lowering, and phase V with contact between the legs and the support surface. The overall pattern of muscle activity was complex with times of EMG onset, peak activity, offset, and duration differing for different muscles. This complex pattern changed qualitatively from one phase to the next, suggesting that the roles of different muscles and, as a consequence, the overall form of coordination, change during the sit-up.
KW - Axial movement
KW - Coordination
KW - EMG
KW - Human
KW - Kinematics
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U2 - 10.1016/S1050-6411(03)00023-3
DO - 10.1016/S1050-6411(03)00023-3
M3 - Article
C2 - 12706604
AN - SCOPUS:0037410081
SN - 1050-6411
VL - 13
SP - 239
EP - 252
JO - Journal of Electromyography and Kinesiology
JF - Journal of Electromyography and Kinesiology
IS - 3
ER -