Figure 4. The time coefficient patterns and activation regions of each principal component across the two shooting phases in the elite and amateur groups. (a) and (b) represent Phase 1 and Phase 2 of the instep kick, respectively. Solid lines indicate positive time coefficients, whereas dashed lines indicate negative time coefficients. Red arcs denote the primary activation region of PC1, orange arcs denote the primary activation region of PC2, light yellow arcs denote the primary activation region of PC3, light blue arcs denote the primary activation region of PC4, sky blue arcs denote the primary activation region of PC5, and dark blue arcs denote the primary activation region of PC6. Black arcs highlight regions with significant activation differences between the elite and amateur groups.