The learning of isometric force time scales is differentially influenced by constant and variable practice

Abstract

This experiment was set up to investigate the influence of constant and variable practice on performance accuracy and the time- and frequency-dependent structure of the force output dynamics in the learning of an irregular isometric force pattern. Traditional approaches to the variability of practice hypothesis have demonstrated benefits of task-induced variability at the outcome level of behavior, but there have been limited investigations of the effect of practice conditions on movement execution and particularly the multiple time scale processes of force output. During the practice phase, variability was induced along the force-time dimension of the target pattern for the variable practice condition (different wave forms), but the wave forms exhibited the same distributional properties of the frequency content (1/f noise: β = -1.5) as the constant practice condition. The results showed that both practice conditions exhibited similar reductions in task error as a function of practice. However, constant practice produced greater changes in the time- and frequency-dependent properties of force output than variable practice, including a higher relative change in the contribution from faster (4-12 Hz) time scale mechanisms. Generalization tests to novel target patterns revealed that the task dynamics had a greater influence than the effect of practice conditions. Collectively, the findings support the adaptive nature of force output structure and the perspective that practice conditions can produce differential effects on the outcome and execution levels of motor behavior.

Effects of practice variability on spinal manipulation learning*

“…Differences between constant practice and variable practice could perhaps be observed after longer practice periods and/or with a longer interval between the posttest and the retention test. Furthermore, the present study only evaluated the effects of task-induced variability at the goal level on participants' capacity to achieve a preselected goal after a practice period, based on the fact that previous studies reported a deleterious effect of task-induced variability when the transfer situation 25,26 or execution level 23 was evaluated. Nevertheless, effects of task-induced variability at the execution level (variable ways to perform SM) or in a transfer task condition (eg, a different or variable peak force) can also be relevant in SM training.…”

“…These schemas consist in the development of relationships between a predefined goal and the parameters used to achieve this goal (retention situation) or a similar one (transfer situation). Consequently, effects of task-induced variability at the goal level (eg, varying force or velocity targets) or the execution level (ie, ways to achieve a given goal) have been studied in several motor skills, including tennis drive, 19 unimanual arm rotation, 20 manual aiming, 21,22 hand force production, 23,24 volleyball serve, 25 and shoulder adduction. 26 Although not consistent, 24 task-induced variability at the goal level typically results in lower accuracy and consistency, as measured by the absolute, 19,22 constant error, 19 or the root-mean-square jerk 20 immediately after the learning period.…”

Selective visual scaling of time-scale processes facilitates broadband learning of isometric force frequency tracking

“…The target pattern was characterized by a fractal dimension that consisted of frequency content from 0-12 Hz and exhibited a spectral slope (~1.5) between pink and brown noise. The wave form was constructed according to fractional Brownian motion (see King & Newell, 2013;). The target line mean was matched to 10 % of the participant's MVC, and the amplitude of the waveform was scaled to ±5 % of the participant's MVC.…”

“…During trials, participants were instructed to maintain a fixed position of the fingers, hand, and forearm against the table. The experimental setup was similar to King and Newell (2013).…”

“…With respect to motor learning, several investigations have shown a persistent change of isometric force structure as a function of practice (Newell, Broderick, Deutsch, & Slifkin, 2003;Sosnoff & Voudrie, 2009); however, only recently have studies explored the effect of different practice conditions on the learning and transfer of isometric force control (King & Newell, 2013;Studenka et al, 2014). The aim of present study was to examine the effect of different informational constraints on the learning and transfer of isometric force dynamics.…”