The Effect of Protective Mat Thickness on the Upper Limb Strike Force Simulation in Combat Sports and Self Defense

The strike force in combat sports strongly depends on the protective material's mechanical properties and energy absorption capacity. Therefore, this study aimed to estimate the effect of the protective layer thickness and repeated loading on the net force in a falling weight impact test. A falling 8-kg weight dropped from 15 cm, 25 cm, and 50 cm was used to simulate impact peak forces in an upper limb strike. Transfer linear regression functions were identified for three layers of different thickness (1.8 cm, 3.6 cm, and 5.4 cm) between the measured force and undamped force that would be measured if no protective layer was used. A decrease in damping performance under repetitive loading was assessed for the same amount of energy (30 J) absorbed by the specimens. There were 36 specimens examined in 126 tests. When the measuring apparatus was covered with one, two or three layers of Trocellen foam, the undamped force was approximately 2.8, 6.1, and 11.1 times higher, respectively (p < 0.05, R² ≥ 0.95), than the force measured in the kinetic design. This allows researchers to select the number of layers according to the individual needs in terms of safety and injury prevention. A single layer of Trocellen foam used in this study may be insufficient to ensure the safety of athletes in upper limb strike experiments due to possible compaction of the foam structure for deformations exceeding 80% compression and forces exceeding 5 kN, although no injury was previously observed.