Effort-dependent effects on uniform and diverse muscle activity features in skilled pitching.

How do skilled players change their motion patterns depending on motion effort? Pitchers commonly accelerate wrist and elbow joint rotations via proximal joint motions. Contrastingly, they show individually different pitching motions, such as in wind-up or follow-through. Despite the generality of the uniform and diverse features, effort-dependent effects on these features are unclear. Here, we reveal the effort dependence based on muscle activity data in natural three-dimensional pitching performed by skilled players. We extract motor modules and their effort dependence from the muscle activity data via tensor decomposition. Then, we reveal the unknown relations among motor modules, common features, unique features, and effort dependence. The current study clarifies that common features are obvious in distinguishing between low and high effort and that unique features are evident in differentiating high and highest efforts.

Precise force controls enhance loudness discrimination of self-generated sound.

Motor executions alter sensory processes. Studies have shown that loudness perception changes when a sound is generated by active movement. However, it is still unknown where and how the motor-related changes in loudness perception depend on the task demand of motor execution. We examined whether different levels of precision demands in motor control affects loudness perception. We carried out a loudness discrimination test, in which the sound stimulus was produced in conjunction with the force generation task. We tested three target force amplitude levels. The force target was presented on a monitor as a fixed visual target. The generated force was also presented on the same monitor as a movement of the visual cursor. Participants adjusted their force amplitude in a predetermined range without overshooting using these visual targets and moving cursor. In the control condition, the sound and visual stimuli were generated externally (without a force generation task). We found that the discrimination performance was significantly improved when the sound was produced by the force generation task compared to the control condition, in which the sound was produced externally, although we did not find that this improvement in discrimination performance changed depending on the different target force amplitude levels. The results suggest that the demand for precise control to produce a fixed amount of force may be key to obtaining the facilitatory effect of motor execution in auditory processes.

Cross-sectional comparison of the probabilistic structure in the distribution of pitching location among baseball pitchers of different ages.

The present study was a cross-sectional comparison of probabilistic structure in the distribution of pitching location among baseball pitchers of various age groups (25 elementary school (ES), 20 junior high school (JH), 15 high school (HS), and 18 college students (CL)). In the results, despite the general age-dependent variations in pitching precision, the difference was reflected not only in error 'size' but also in the 'shape' of error as it was shown by fitting 95% confidence ellipse to the two dimensional distribution of pitch location. While the precision measure as a reflection of trial-by-trial variability of release timing (major axis length of the ellipse) was constant, minor axis length of the ellipse as a reflection of variability in the pitching form of each participant demonstrated significant differences among the groups. In the ES group particularly, the trial-by-trial variability in the trajectory angle of the throwing arm was significantly correlated with the minor axis length; this correlation was far greater than those in older groups. The present study is the first to demonstrate the detailed structure of the variability of pitching location of baseball dependent on age.

Interpersonal variability in timing strategy and temporal accuracy in rapid interception task with variable time-to-contact.

In rapid interceptive actions such as hitting a baseball, cricket ball or tennis ball, ball speed varies between trials, and players have to compensate the time lag by controlling the moment of movement onset and movement duration. Previous studies have found that these two variables can flexibly co-vary and are robustly influenced by target speed (i.e. velocity-coupling effect: faster movement for faster target). However, some studies reported an interpersonal variability in the timing control strategy and the relationship between the strategy and temporal accuracy in rapid interception is unclear. We used a baseball-simulated rapid interceptive task to assess this issue. Under relatively easy time constraints, there was a large interpersonal variability, and participants were distinctively divided into two groups: those who mainly modulated their movement duration and those who mainly controlled their movement onset. When the time constraint became severe, the second strategy shifted to the first strategy in most of the second group participants. In the both cases, being able to mainly control movement onset resulted in higher temporal accuracy. These results suggest that minimising the velocity-coupling effect is an important factor to achieve high temporal accuracy in rapid interception.