Measuring movement irregularity in the upper motor neurone syndrome using normalised average rectified jerk

Spatial resolution of spontaneous accelerations in reaching tasks

“…An antithetical relationship between MAPR and normalized average jerk has been reported elsewhere, but causality has been attributed to various other phenomena, such as the blending of sub-movements (Krebs et al, 1999;Goldvasser et al, 2001;Rohrer et al, 2002). Jerk normalization is considered necessary in order to eliminate bias due to average velocity or total range of motion (Rohrer et al, 2002;Cozens and Bhakta, 2003), and alternate formulations have been proposed where total movement duration is penalized (Hoff, 1994;Engelbrecht, 2001). However, in movements with prolific stall behavior, time-normalized jerk and related metrics may actually decrease in spastic movements due to a preponderance of zero-jerk activity during stall periods.…”

“…The finding of significantly reduced smoothness within a small cohort of hemiparetic subjects demonstrates the discriminative power of scalar metrics derived from SAT maps as opposed to jerkbased metrics, which failed to discriminate between cohorts at the Po0.05 level, and do not reliably co-vary with other smoothness measures (Goldvasser et al, 2001;Rohrer et al, 2002;Cozens and Bhakta, 2003).…”

“…speed on jerk score (Cozens and Bhakta, 2003). In concordance with standard practice, each differentiation was smoothed with filter characteristics identical to those defined above; trapezoidal integrals were computed.…”

The role of cutaneous sensation in the motor function of the hand

“…The measured length of the trajectory is expressed relative to the target length. The jerk (1) is defined as the rate of change of acceleration, the third derivative of distance x with respect to time t (J = d3x/dt'), and the integruled jerk ( = J IJJ dt) averages this over the whole movement segment [3]; to correct for differences in duration we calculate the normalised uueruge rectified jerk = J IJI dt x duration* [3]. We also measured the force delivered by the pen over the digitizer.…”

Restoration of occlusal and proximal contacts by a single molar crown improves the smoothness of the masticatory movement

“…The smoothness of the movement is related to the regularity in the movement jerk, where the jerk is the rate of change in movement acceleration/ deceleration. Quantifications of the irregularities or tremors of movement trajectory in terms of the movement jerk have allowed not only valid discrimination between the movement characteristics for individuals with/without motor dysfunctions [12][13][14][15][16][17] but also the detection of the movements under development or in an adaptive process. [18][19][20] Therefore, the jerk-cost, defined as a time integral of the squared jerk during motion, has been universally accepted as the specific movement objective.…”