TY  - JOUR
AU  - Tibold, Róbert
AU  - Fazekas, Gábor
AU  - Laczkó, József
TI  - Three-Dimensional Model to Predict Muscle Forces and Their Relation to Motor Variances in Reaching Arm Movements
JF  - JOURNAL OF APPLIED BIOMECHANICS
J2  - J APPL BIOMECH
VL  - 27
PY  - 2011
IS  - 4
SP  - 362
EP  - 374
PG  - 13
SN  - 1065-8483
DO  - 10.1123/jab.27.4.362
UR  - https://m2.mtmt.hu/api/publication/1854515
ID  - 1854515
AB  - A three-dimensional (3-D) arm movement model is presented to simulate kinematic properties and muscle forces in reaching arm movements. Healthy subjects performed reaching movements repetitively either with or without a load in the hand. Joint coordinates were measured. Muscle moment arms, 3-D angular acceleration, and moment of inertias of arm segments were calculated to determine 3-D joint torques. Variances of hand position, arm configuration, and muscle activities were calculated. Ratios of movement variances observed in the two conditions (load versus without load) showed no differences for hand position and arm configuration variances. Virtual muscle force variances for all muscles except deltoid posterior and EMG variances for four muscles increased significantly by moving with the load. The greatly increased variances in muscle activity did not imply equally high increments in kinematic variances. We conclude that enhanced muscle cooperation through synergies helps to stabilize movement at the kinematic level when a load is added.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Keresztenyi, Z
AU  - Cesari, P
AU  - Fazekas, Gábor
AU  - Laczkó, József
TI  - The relation of hand and arm configuration variances while tracking geometric figures in Parkinson's disease: aspects for rehabilitation
JF  - INTERNATIONAL JOURNAL OF REHABILITATION RESEARCH
J2  - INT J REHABIL RES
VL  - 32
PY  - 2009
IS  - 1
SP  - 53
EP  - 63
PG  - 11
SN  - 0342-5282
DO  - 10.1097/MRR.0b013e32830d369c
UR  - https://m2.mtmt.hu/api/publication/1854524
ID  - 1854524
AB  - Variances of drawing arm movements between patients with Parkinson's disease and healthy controls were compared. The aim was to determine whether differences in joint synergies or individual joint rotations affect the endpoint (hand position) variance. Joint and endpoint coordinates were measured while participants performed drawing tasks. Variances of arm configurations and endpoints were computed and statistically analyzed for 12 patients and 12 controls. The variance of arm movements for patients (both for arm configuration and endpoint) was overall higher than that for the control group. Variation was smaller for drawing a circle versus a square and for drawing with the dominant versus the nondominant hand within both groups. The ratio of arm configuration variances between groups was similar to the ratio of endpoint variances. There were significant differences in the velocity, but not in the path lengths of movements comparing the two groups. Patients presented less movement stability while drawing different figures in different trials. Moreover, the similarity of the ratios suggests that the ill-coordinated hand movement was caused by the error in the movements of individual body parts rather than by the lack of intersegmental coordination. Thus, rehabilitation may focus on the improvement of the precision of individual joint rotations.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Laczkó, József
AU  - Walton, K
AU  - Llinas, R
TI  - A neuro-mechanical transducer model for controlling joint rotations and limb movements
JF  - CLINICAL NEUROSCIENCE RESEARCH
J2  - CLIN NEUROSCI RES
VL  - 59
PY  - 2005
IS  - 1-2
SP  - 32
EP  - 43
PG  - 12
SN  - 1566-2772
UR  - https://m2.mtmt.hu/api/publication/140377
ID  - 140377
LA  - English
DB  - MTMT
ER  -