Random, Timed, and Self-Paced: How Preparation Time Affects the Loading of the Body Prior to Flight in a Two-Footed Forward Jump
Although numerous studies have replicated Fitts speed-accuracy trade-off relationship in reciprocal and discrete tasks, little research to date has examined the applicability of this lawful assessment on whole body ballistic tasks, such as jumping. A study by Juras et al., (2009) suggests that the lawful relationship is violated in ballistic jumping by showing no differences in movement time when target width decreased. Additionally, the authors suggest that the kinematics of the jump are pre-programmed prior to the execution of the movement. A recent study by Boyle and colleagues (2016) furthered this idea by showing an inverse relationship between the height of the participant’s center of mass (Hcom) and the index of difficulty (ID). As the ID increased, the Hcom decreased. The authors suggest the self-paced nature of the task may be causing the effect. In the current study, three conditions involved participants making two footed forward jumps to targets of 6 in. and 3in. in width, at 30% and 60% maximal horizontal distance (MHD) of a maximal jump. Additional categories regarding the control characteristics of the “go” signal were divided in to: Self-paced, Timed and Random. Three kinematic variables (jump initiation, flight, and total time) were recorded, as well as participant center of mass height (Hcom) and maximum flight trajectory height of Hcom. The results agree with the previous studies, showing a decrease in Hcom as ID increases. Self-paced displayed the lowest Hcom between all groups but also performed the movement the slowest where participants in the timed condition produced the fastest movement times followed by random and then self-paced.^
Stewart, Dorothy Marie, "Random, Timed, and Self-Paced: How Preparation Time Affects the Loading of the Body Prior to Flight in a Two-Footed Forward Jump" (2018). ETD Collection for University of Texas, El Paso. AAI10822472.