Arm Swing and External Load Reorganize Force–Time Strategy in Collegiate Basketball Players: Associations with Force Production Capacity

Background: Vertical jump force–time strategy describes how force is organized in time. This strategy provides performance-relevant information that jump height alone does not capture in basketball players. Arm swing and external load are opposing conditions rarely imposed on the same athletes. However, little is known about how they reorganize jump strategy, or whether force production capacity is associated with the response. Methods: A within-participant, repeated-measures design was used. Seventeen collegiate male basketball players performed the countermovement jump (CMJ), the arm-swing countermovement jump (CMJA), and the 20 kg loaded countermovement jump (LCMJ) on force platforms in a fixed order within one session. The isometric mid-thigh pull provided relative peak force and the rate of force development (RFD250). Vastus lateralis and lateral gastrocnemius architecture were assessed by ultrasonography. Linear mixed-effects models examined condition effects and capacity associations, with a condition-mean sensitivity analysis. Results: Relative to CMJ, CMJA increased jump height and prolonged contact and concentric times. In contrast, LCMJ reduced jump height and increased mean concentric force. No significant overall condition effect was found for gross peak force, and equivalence was not established. Relative isometric peak force was not significantly associated with jump height. The trial-level CMJA-by-RFD250 interaction was significant, but the corresponding interaction was not significant in the condition-mean model. No architecture–RFD250 correlation remained significant after correction for multiple comparisons. Conclusions: In this exploratory fixed-order design, the arm-swing and loaded conditions were associated with divergent force–time responses. Evidence for an overall condition effect on gross peak force was inconclusive, and the capacity associations require confirmation in larger, counterbalanced samples.