Task constraints and stepping movement of fast-pitch softball hitting

This study aims to clarify the relationship between task constraints and the preparatory movement of fast-pitch softball batters in Japan for three different competition categories, namely high school, college, and league. As task constraints, we focused on the temporal and tool constraints and evaluated preparatory movements using initiation time and step duration of the stepping movement in a striking action. First, we confirmed the temporal constraints in each category and then examined the relationship between the temporal constraints and the stepping movements. The results demonstrated that the temporal constraints affected both initiation time and step duration of the stepping movements. Hierarchical cluster analysis was applied to the two variables. Consequently, the stepping movement of the softball players was classified into three types: “late initiation–short duration” (LS), “early initiation–short duration” (ES), and “early initiation–long duration” (EL) corresponding to the task constraints. Finally, the relationship between the task constraints of each category and the stepping movements was examined. The results revealed that high school players exhibited mostly the LS- or EL-type stepping movement; college players exhibited mostly the EL-type stepping movement; and league players exhibited all types. These results depict that the players in each category with each temporal and tool constraint exhibited particular types of stepping movements as a preparatory movement corresponding to each task constraint, thereby arguing that players use a not-to-lose strategy exploiting the redundancy in solutions under various task constraints.本研究旨在明确日本快投垒球击球手在三类不同赛事组别（高中组、大学组及联赛组）中的任务约束与预备动作间的关联。本研究聚焦于时间约束与工具约束两类任务约束指标，并通过击球动作中跨步动作的启动时机与跨步时长，对预备动作进行量化评估。首先，本研究验证了各赛事组别的时间约束特征，随后分析了时间约束与跨步动作间的关联。研究结果显示，时间约束对跨步动作的启动时机与跨步时长均存在显著影响。本研究对上述两项变量开展分层聚类分析（Hierarchical Cluster Analysis），最终根据任务约束将垒球运动员的跨步动作划分为三类："启动延迟-短时长（LS, Late Initiation–Short Duration）"、"启动提前-短时长（ES, Early Initiation–Short Duration）"以及"启动提前-长时长（EL, Early Initiation–Long Duration）"。最后，本研究进一步分析了各赛事组别任务约束与跨步动作间的关联。结果表明：高中组运动员多采用LS型或EL型跨步动作；大学组运动员主要采用EL型跨步动作；而联赛组运动员则覆盖全部三类动作类型。上述研究结果证实，不同赛事组别的运动员在匹配各自的时间与工具约束时，会呈现出与对应任务约束相符的特定跨步预备动作类型，由此表明运动员在多样的任务约束下，会通过利用解决方案的冗余性来采取不败策略。