Energy flow differences at the joints of the throwing arm between javelin and weighted balls in male javelin throwers

Hans-Peter Köhler^1*Kristof Kipp²Nikola Prvulović³Maren Witt¹

• ¹Leipzig University, Leipzig, Germany
• ²Marquette University, Milwaukee, United States
• ³Univerzitet u Beogradu, Belgrade, Serbia

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 exhibit substantially greater kinetic energy at the moment of release, despite markedly lower release velocities. The primary objective of the present investigation was to analyze the energy transfer within the throwing arm in order to gain deeper insight into the biomechanical mechanisms underlying the use of implements with different masses. For this purpose, the three-dimensional coordinates of 16 reflective markers were recorded for six athletes during throws using six different implement masses. The motion was recorded 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 non-linear temporal registration and statistical non-parametric mapping. 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 more distal joints. These 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 a 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.