Different spatio-temporal strategies for controlling a striking gesture to slide an object toward a target distance

Humans never perform the same movement twice, and there is interindividual variability in the spatio-temporal regulation of movements. The objective of the present study was to investigate the relationship between spatio-temporal strategies and motor coordination strategies involved in controlling the impact speed during a striking gesture. The literature suggests three distinct strategies for spatio-temporal control of the ballistic strike to cope with task demand: varying strike amplitude while keeping duration constant; keeping amplitude constant while modulating duration; or adjusting both to change impact acceleration. In this study, participants (n = 33) struck a cube sliding toward a target distance under varying task demands. K-Means clustering and correlational analyses identified three distinct strategies, none of which matched the "constant amplitude" strategy. Regression analyses confirmed that strike duration was modulated differently by cluster as a function of impact speed. While clusters exploited strike amplitude and duration differently, impact speed was the common control variable across clusters, which did not differ in mean performance (spatial error). Hierarchical Multiple Factor Analysis validated these strategies ("Inverse Duration-Amplitude", "Temporal Invariance", and "Late-Impulse") by distinguishing between-cluster differences from within-cluster variability. Dimensions 1 and 2 differentiated strategies via mean amplitude and temporal scaling rules. Conversely, Dimensions 3 and 4 captured within-cluster variability in the combined magnitude of amplitude and duration, and impact speed intensity, respectively. Results show that, despite individual differences in movement scale, participants adopt robust strategies to regulate impact speed in response to task demands. Finally, we found that spatio-temporal strategies and motor coordination are independent.