Physical principles for economies of skilled movements

Abstract

This paper presents some elementary principles regarding constraints on movements, which may be useful in modeling and interpreting motor control strategies for skilled movements. Movements which are optimum with respect to various objectives, or "costs", are analyzed and compared. The specific costs considered are related to movement time, distance, peak velocity, energy, peak acceleration, and rate of change of acceleration (jerk). The velocity patterns for the various minimum cost movements are compared with each other and with some skilled movement patterns. The concept of performance trade-offs between competing objectives is used to interpret the distance-time relationships observed in skilled movements. Examples of arm movements during violin bowing and jaw movements during speech are used to show how skilled movements are influenced by considerations of physical economy, or "ease", of movement. Minimum-cost solutions for the various costs, which include the effect of frictional forces, are given in Appendices.

Kinematic form and scaling: Further investigations on the visual perception of lifted weight.

“…However, the standard in Runeson and Frykholm (1981) was assigned a nonarbltrary value on the metric scale of weight that apparently indexed the appropriate scale for subsequent judgments. On the assumptmn that the standard prowdes the enUre ' The "phase plane" is a graph of velocity versus position See, for example, McGmms and Newell (1982) and Nelson (1983) 2 Hollerbach and Flash (1982) demonstrate velooty scahng wRhout change of form m a velocRy-Ume plot, however, the present study revolves the form ofa velocRy-posRlon plot. What are the essennal properues that might chsnngmsh among phase plane forms9 Can&dates mdude symmetry properties, the number of cnUcal points m the curve, and the specific behavmr of various denvaUves along the curve prowdmga local description of its shape (O'Neill, 1966) Phase plane curves for human hmb movements typically are unlmodal vath a single point of mflectmn, bilateral symmetry, and restricted vanaUons along the curve m both curvature and rate of change of curvature Peak velooty of movement is represented by the height of the velocRy-poslUon curve at the mflecUon point Tins height can be scaled to a degree determined by the amphtude wRhout appreoable change m the curvature or rate of change of curvature along the curve By contrast, a change m lanemaUc form could mean allowing the rate of change m curvature to mcrease sharply at points bounding a porUon of the curve along winch curvature approaches zero The resulting curve would look more hke a square than a sem~orcle basis for scaling, the displays would specify only ordinal relations among lifted weight values.…”

Drawing ellipses in water: evidence for dynamic constraints in the relation between velocity and path curvature

“…This model assumes that the cost function being minimized includes both an external and an internal jerk function, with the result that changes in overall stiffness and/or viscosity will affect the specific form of the velocity-curvature relationship (Wann et al 1988). We believe that control laws incorporating dynamic terms, such as the modified minimum-jerk (Wann et al 1988), minimumenergy (Nelson 1983), or minimum-torque-change (Uno et al 1989), can account for the changes of the exponent in the velocity-curvature relationship we observed with changes of the medium viscosity.…”

Interactive cervical motion kinematics: Sensitivity, specificity and clinically significant values for identifying kinematic impairments in patients with chronic neck pain

“…Time to peak velocity percentage (TTPP) was defined as the time from motion initiation to the peak velocity moment, as a percentage of total movement time. Relative time to peak velocity has been studied in human motion, and is considered optimal when presenting a symmetric bell-shape velocity profile with a 1:1 acceleration-deceleration ratio, or in other words a 50% TTPP (Nelson, 1983, Hogan, 1984. Previous findings relating to TTPP in symptomatic neck motion were inconsistent which emphasised the need for further investigation (Roijezonet al, 2010, Sarig Bahat et al , 2014b.…”