TY - JOUR
T1 - Scaling and non-scaling of muscle activity, kinematics, and dynamics in sit-ups with different degrees of difficulty
AU - Cordo, Paul J.
AU - Hodges, Paul W.
AU - Smith, Terrence C.
AU - Brumagne, Simon
AU - Gurfinkel, Victor S.
N1 - Funding Information:
The authors gratefully acknowledge support for this research from the NIH (R01 AR40067 and AR31017) for P.C., V.G., and T.S., the NHMRC of Australia for P.H., and the Research Council of the KU Leuven for S.B.
PY - 2006/10
Y1 - 2006/10
N2 - The purpose of this study was to investigate how the CNS adjusts motor patterns for variants of a complex axial movement-the sit-up. Adjustments were induced by changing the support surface contact and mass distribution of the body. Healthy adults performed straight-legged sit-ups, 3 s in duration, with support added to or removed from the lumbar trunk, or with mass added to the head or to the legs. Each of these interventions either increased or decreased the difficulty of the task. The study addressed the extent to which changes in sit-up difficulty are compensated by scaling of muscle activity, kinematics, and dynamics versus the extent to which they are compensated by changing discretely the motor pattern. The analysis of muscle activity, kinematics, and dynamics focused on the first 30-40% of the sit-up-the trunk flexion phase-since this is the most critical part of the movement. Our results demonstrate that, in some respects, sit-up kinematics and dynamics scaled with difficulty, but in other respects, they did not. Muscle activity also scaled, in many respects, but in more difficult sit-ups, abdominal flexor activity decreased instead of increased. Non-scaling changes in these parameters suggest that complex movements, such as the sit-up, may require discrete changes in motor pattern in order to deal with large loads, which challenge the available leverage.
AB - The purpose of this study was to investigate how the CNS adjusts motor patterns for variants of a complex axial movement-the sit-up. Adjustments were induced by changing the support surface contact and mass distribution of the body. Healthy adults performed straight-legged sit-ups, 3 s in duration, with support added to or removed from the lumbar trunk, or with mass added to the head or to the legs. Each of these interventions either increased or decreased the difficulty of the task. The study addressed the extent to which changes in sit-up difficulty are compensated by scaling of muscle activity, kinematics, and dynamics versus the extent to which they are compensated by changing discretely the motor pattern. The analysis of muscle activity, kinematics, and dynamics focused on the first 30-40% of the sit-up-the trunk flexion phase-since this is the most critical part of the movement. Our results demonstrate that, in some respects, sit-up kinematics and dynamics scaled with difficulty, but in other respects, they did not. Muscle activity also scaled, in many respects, but in more difficult sit-ups, abdominal flexor activity decreased instead of increased. Non-scaling changes in these parameters suggest that complex movements, such as the sit-up, may require discrete changes in motor pattern in order to deal with large loads, which challenge the available leverage.
KW - Axial movement
KW - Coordination
KW - EMG
KW - Human
KW - Kinematics
KW - Perturbations
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U2 - 10.1016/j.jelekin.2005.10.005
DO - 10.1016/j.jelekin.2005.10.005
M3 - Article
C2 - 16403653
AN - SCOPUS:33745222712
SN - 1050-6411
VL - 16
SP - 506
EP - 521
JO - Journal of Electromyography and Kinesiology
JF - Journal of Electromyography and Kinesiology
IS - 5
ER -