Interlimb and within limb force coordination in static bimanual manipulation task

Abstract

The aim of the study was to compare the coordination of hand grip (G) and load force (a force that tends to cause slippage of a grasped object; L) in static bimanual manipulation tasks with the same data obtained from the similar dynamic tasks. Based on the previous findings obtained from dynamic tasks, it was hypothesized that an increase in the rate of L change would be predominantly associated with a decrease in the coordination of the within limb forces (coordination of G and L of each hand as assessed through the correlation coefficients), while a decrease in coordination of interlimb forces (between two G and two L) will be less pronounced. Regarding the pattern of modulation of G, the same increase in L frequency was also expected to be associated with a decrease in G gain and an increase in G offset (as assessed by slope and intercept of the regression lines obtained from G to L diagrams, respectively), as well as with an increase in average G/L ratio. Subjects exerted oscillatory isometric L profiles by simultaneous pulling out two handles of an externally fixed device under an exceptionally wide range of L frequencies (0.67-3.33 Hz). The results demonstrated relatively high correlation coefficients between both the interlimb and within limb forces that were only moderately affected under sub-maximal L frequencies. Furthermore, the hypothesized changes in G gain and offset appeared only under the highest L frequency, while the G/L ratio remained unaffected. We conclude that, when compared with the dynamic tasks based on the unconstrained movements of hand-held objects that produce similar pattern of L change, the static manipulation tasks demonstrate a consistent and highly coordinated pattern of bilateral G and L under a wide range of frequencies. However, the neural mechanisms that play a role in the revealed differences need further elucidation.

Impaired Object Manipulation in Mildly Involved Individuals with Multiple Sclerosis

“…In the oscillatory task, the participants were instructed to exert an oscillatory pattern of L by pulling upward against the handles (pull up and relax) paced by a metronome set at 1.33 Hz. According to our previous findings, this frequency was within the comfortable range (Jaric, Collins, Marwaha, & Russell, 2006). The duration of each trial was 12 s (i.e., approximately 16 periods).…”

“…In the oscillatory task, the participants were instructed to exert an oscillatory pattern of L by pulling upward against the handles (pull up and relax) paced by a metronome set at 1.33 Hz. According to our previous findings, this frequency was within the comfortable range (Jaric, Collins, Marwaha, & Russell, 2006 Both static manipulation tasks were performed with and without visual feedback. Under the visual feedback condition, a computer monitor placed in front of the participants showed either the prescribed profile (in the ramp-and-hold task) or two horizontal lines depicting the upper and lower level for the oscillatory force profile, as well as the current average L exerted by the subject's two hands.…”

“…In the ramp-and-hold task (the ramp phase) and oscillation task, the coupling of G and L was assessed by calculating the maximum cross-correlation coefficients between the time series of G and L (Flanagan & Tresilian, 1994;Marwaha, Hall, Knight, & Jaric, 2006). However, similar to the findings of previous studies (Jaric, Collins, Marwaha, & Russell, 2006;Jaric, Russell, Collins, & Marwaha, 2005), the time lags appeared to be exceptionally small and inconsistent for all three tasks, demonstrating no significant effects even at the level of p < .1. Therefore, the maximum correlation coefficients alone were taken for further analysis (see Marwaha, Hall, Knight, & Jaric, 2006, for a similar approach).…”

“…Since the opposite result could be expected from a healthy population, the availability of visual feedback when producing a prescribed L profile could have different effects on MS patients than on healthy individuals. Finally, we have recently shown that the coordination of G and L in static manipulation tasks (Jaric, Collins, Marwaha, & Russell, 2006) could be less affected by task complexity than the same coordination in tasks performed with free-moving objects (c.f., Zatsiorsky, Gao, & Latash, 2005). Therefore, testing of both The main aim of our study was to assess specific aspects of impairment of hand function in mildly involved MS patients in both static and dynamic manipulation tasks.…”

Prehension Synergies in the Grasps With Complex Friction Patterns: Local Versus Synergic Effects and the Template Control

“…Conceptually, the k i (3) coefficients are similar to the grip force:load force ratio broadly used in studies on grasping (Burstedt et al 1999;Jaric et al 2005Jaric et al , 2006Johansson and Westling 1984;Serrien and Wiesendanger 2001). The k i (3) coefficients are computed, however, for the individual digits, not for the total grip force.…”