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Steinhart, S., Weiss, P. L., & Friedman, J. (2021). Proximal and distal movement patterns during a graphomotor task in typically developing children and children with handwriting problems. J Neuroeng Rehabil, 18(1), 178.
Abstract: BACKGROUND: Therapists specializing in handwriting difficulties in children often address motor problems including both proximal and distal movements in the upper extremity. Kinematic measures can be used to investigate various aspects of handwriting. This study examined differences in movement patterns in proximal and distal joints of the upper extremity during graphomotor tasks between typically developing children with and without handwriting problems. Additionally, it explored relationships between movement patterns, speed, and legibility of writing. METHODS: Forty-one children, aged 7-11 years, were assessed with the Aleph Aleph Ktav Yad Hebrew Handwriting assessment and the Beery Test of Visual Motor Integration and, based on their scores, were divided into a research group (with handwriting difficulties) and a control group (without handwriting difficulties). Upper extremity joint movement patterns were analyzed with a motion capture system. Differences in the quality of shapes traced and copied on a graphics tablet positioned horizontally and vertically were compared. Between-group differences and relationships with speed and legibility were analyzed. RESULTS: In both groups, there was greater movement in the distal compared to the proximal joints, greater movement when performing the task in a horizontal compared to a vertical plane, and greater movement when tracing than copying. Joint movements in the arm executed scaled-down versions of the shapes being drawn. While the amount of joint displacement was similar between groups, children in the research group showed greater dissimilarity between the drawn shape and the shape produced by the proximal joints. Finally, the drawing measure on the tablet was a significant predictor of legibility, speed of writing, visual motor integration and motor coordination, whereas the dissimilarity measure of joint movement was a significant predictor of speed of writing and motor coordination. CONCLUSIONS: This study provides support for the role of the distal upper extremity joints in the writing process and some guidance to assist clinicians in devising treatment strategies for movement-related handwriting problems. While we observed differences in proximal joint movements between the children with and without handwriting difficulties, the extent to which they are responsible for the differences in drawing quality remains to be determined. Further studies should use a similar methodology to examine additional tasks such as drawing shapes of varying sizes.
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Liebermann, D. G., Berman, S., Weingarden H., Levin, M. F., & Weiss, P. L. (2009). Kinematic features of arm and trunk movements in stroke patients and age-matched healthy controls during reaching in virtual and physical environments. In Virtual Rehabilitation International Conference (pp. 179–184).
Abstract: Motor performance of stroke patients and healthy individuals was compared in terms of selected kinematic features of arm and trunk movements while subjects reached for visual targets in virtual (VR) and physical (PH) environments. In PH, the targets were placed at an extended arm distance, while in VR comparably placed virtual targets were presented via GestureTek's IREX system. Our goal was to obtain further insights into research methods related to VR-based rehabilitation. Eight right-hemiparetic stroke patients (age =46-87 years) and 8 healthy adults (age =51-73 years) completed 84 reaching movements in VR and PH environments while seated. The results showed that arm and trunk movements differed in the two environments in patients and to a lesser extent in healthy individuals. Arm motion of patients became jerkier in VR, with larger paths and longer movement durations, and presented greater arm torsion (i.e., larger elbow rotations around the hand-shoulder axis). Interestingly, patients also showed a significant reduction of compensatory trunk movements during VR reaching. The findings indicate that when targets were perceived to be beyond hand reach, stroke patients may be less able to estimate 3D virtual target locations obtained from the 2D TV planar displays. This was not the case for healthy participants.
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Liebermann, D. G., Raz, T., & Dickinson, J. (1988). On Intentional and Incidental Learning and Estimation of Temporal and Spatial Information. Journal of Human Movement Studies, 15, 191–204.
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Liebermann, D. G., & Goodman, D. (2007). Pre-landing muscle timing and post-landing effects of falling with continuous vision and in blindfold conditions. J Electromyogr Kinesiol, 17(2), 212–227.
Abstract: The present study examined the effect of continuous vision and its occlusion in timing of pre-landing actions during free falls. When vision is occluded, muscle activation is hypothesized to start relative to onset of the fall. However, when continuous vision is available onset of action is hypothesized to be relative to the moment of touchdown. Six subjects performed 6 randomized sets of 6 trials after becoming familiar with the task. The 36 trials were divided in 2 visual conditions (vision and blindfold) and 3 heights of fall (15, 45 and 75 cm). EMG activity was recorded from the gastrocnemius and rectus femoris muscles during the falls. The latency of onset (L(o)) and the lapse from EMG onset to touchdown (T(c)) were obtained from these muscles. Vertical forces were recorded to assess the effects of pre-landing activity on the impacts at collision with and without continuous vision. Peak amplitude (F(max)), time to peak (T(max)) and peak impulse normalized to momentum (I(norm)) were used as outcome measures. Within flight time ranges of approximately 50-400 ms, the results showed that L(o) and T(c) follow a similar linear trend whether continuous vision was available or occluded. However, the variability of T(c) for each of the muscles was larger in the vision occluded condition. Analyses of variance showed that the rectus femoris muscle started consistently earlier in no vision trials. Finally, impact forces were not different in vision or blindfold conditions, and thus, they were not affected by minor differences in the timing of muscles prior to landing. Thus, it appears that knowing the surroundings before falling may help to reduce the need for a continuous visual input. The relevance of such input cannot be ruled out for falls from high landing heights, but cognitive factors (e.g., attention to specific cues and anticipation of a fall) may play a dominant role in timing actions during short duration falls encountered daily.
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Latash, M. L., Friedman, J., Kim, S.W., Feldman, A.G., Zatsiorsky, V.M. (2010). Prehension Synergies and Control with Referent Hand Configurations. Exp Brain Res, 202(1), 213–229.
Abstract: We used the framework of the equilibrium-point hypothesis (in its updated form based on the notion of referent configuration) to investigate the multi-digit synergies at two levels of a hypothetical hierarchy involved in prehensile actions. Synergies were analyzed at the thumb-virtual finger level (virtual finger is an imaginary digit with the mechanical action equivalent to that of the four actual fingers) and at the individual finger level. The subjects performed very quick vertical movements of a handle into a target. A load could be attached off-center to provide a pronation or supination torque. In a few trials, the handle was unexpectedly fixed to the table and the digits slipped off the sensors. In such trials, the hand stopped at a higher vertical position and rotated into pronation or supination depending on the expected torque. The aperture showed non-monotonic changes with a large, fast decrease and further increase, ending up with a smaller distance between the thumb and the fingers as compared to unperturbed trials. Multi-digit synergies were quantified using indices of co-variation between digit forces and moments of force across unperturbed trials. Prior to the lifting action, high synergy indices were observed at the individual finger level while modest indices were observed at the thumb-virtual finger level. During the lifting action, the synergies at the individual finger level disappeared while the synergy indices became higher at the thumb-virtual finger level. The results support the basic premise that, within a given task, setting a referent configuration may be described with a few referent values of variables that influence the equilibrium state, to which the system is attracted. Moreover, the referent configuration hypothesis can help interpret the data related to the trade-off between synergies at different hierarchical levels.
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