Energy flow differences in throwing arm joints between javelin and weighted balls in male javelin throwers.

Introduction: To enhance release velocity during competition, javelin throwers incorporate implements of varying mass into their training regimens. Previous research has demonstrated that, although velocity contributes quadratically to the computation of kinetic energy, heavier implements generate substantially greater kinetic energy at the moment of release, despite markedly lower release velocities. The primary objective of the present investigation was to analyze energy transfer within the throwing arm to gain deeper insight into the biomechanical mechanisms underlying the use of implements with different masses. Methods: The three-dimensional coordinates of 16 reflective markers were recorded for 6 athletes during throws using 6 different implement masses, using 12 infrared cameras. Based on this kinematic data, segmental energy transfer was estimated via inverse dynamics using a multi-body modeling approach. Subsequent comparisons were conducted using nonlinear temporal registration and statistical non-parametric mapping. Results: The results indicate that energy flow at the shoulder joint remains largely consistent across implements of varying mass. However, significant differences in energy transfer were observed at the more distal joints. Discussion: The findings suggest that the increased kinetic energy observed with heavier implements arises from an internal redistribution of energy within the throwing arm, rather than from greater overall energy input. Consequently, improvements in release velocity associated with lighter or heavier implements are likely attributable to mechanisms other than modifications in energy flow dynamics.