Abstract
Intentional and reactive movements are dissimilar in terms of execution time. Previous studies reported that reactive movements are faster than intentional movements (“Bohr’s law” or “Gunslinger effect”), however, these studies focused only on hand-reaching tasks, such as pressing buttons. No studies assessed whole-body movements involving movement of the center of mass (CoM). This movement is characterized by many degrees of freedom because it involves many joints and requires more force than the hand-reaching movement. In this study, we determined the differences in the patterns of temporal structure and force exertion to elucidate the mechanism of “Bohr’s law” in whole-body movement involving movement of the CoM. Ten participants performed a sidestepping task, which requires at least two steps: (1) an intentional movement, in which the movement started with the participants’ own timing; and (2) a reactive movement, in which the movement started the moment a light-emitting diode bulb in front of the participants lit up. We collected data on the ground reaction forces and coordinates of 20 body points. The time of movement onset was calculated and defined based on the ground reaction force, which has the earliest onset compared with velocity and position. The execution time was significantly shorter in the reactive movement condition than in the intentional movement condition (772 vs. 715 ms, p = 2.9 × 10–4). We confirmed that Bohr’s law was applicable not only in hand-reaching tasks but also in whole-body movement. Moreover, we identified three phases, including the velocity reversal phenomenon associated with the produced mechanism of Bohr’s law, and provided the temporal structure. The difference in the pattern of force exertion accompanying the two styles of motor planning with different accuracies was strongly associated with this motor characteristic. These findings may serve as important basic data to scientifically clarify the mechanism of complex physical tactics implemented in one-on-one dueling in various sports.
Highlights
One-on-one dueling in sports involves complex physical tactics that rely upon cognitive factors such as decision-making (CañalBruland, 2009; Tsutsui et al, 2019), deception (Brault et al, 2010, 2012), and anticipation (Savelsbergh et al, 2005; Fujii et al, 2014a)
The unique study by Welchman et al (2010) on gunfight scenarios in cowboy films is a representative study of successful simplification of one-on-one dueling. These confrontations are differentiated from those of an attacker and a defender based on who initiates motions. Applying these roles to Welchman et al.’s study, the attacker engages in intentional movement and the defender engages in reactive movement
The differences in the neural basis lead to asymmetry in the time taken to execute a movement
Summary
One-on-one dueling in sports involves complex physical tactics that rely upon cognitive factors such as decision-making (CañalBruland, 2009; Tsutsui et al, 2019), deception (Brault et al, 2010, 2012), and anticipation (Savelsbergh et al, 2005; Fujii et al, 2014a). All studies relevant to Bohr’s law have adopted a relative motion against the center of mass (hand-reaching task), as in cases of pressing buttons (Welchman et al, 2010; Pinto et al, 2011; La Delfa et al, 2013; Roberts et al, 2017; Weller et al, 2018) and throwing karate punches (Martinez de Quel and Bennet, 2014) These tasks have few degrees of freedom because there are only a few joints involved in the movement. We considered it to be more specialized and characterized by a more difficult level of motor control than a karate punch because the subject controls the right and left legs separately, and there is an aerial phase in which both feet are off the ground
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