# Estimating actual striking forces using attenuation properties of Taekwondo protectors

## TL;DR

This study develops a method to estimate real striking forces in Taekwondo by analyzing how body protectors reduce impact forces.

## Contribution

The study introduces a validated method to estimate original impact forces from attenuated data using a pendulum-based system and linear attenuation relationships.

## Key findings

- Impact attenuation ratios were highly consistent across a wide force range (300-5800 Newtons).
- Estimated striking forces from athletes ranged between 1300 to 1800 Newtons using derived attenuation factors.
- The predictive model achieved low error rates (nRMSE of 3.5%) in estimating input forces.

## Abstract

Background: Protectors significantly attenuate impact forces, yet their quantitative characteristics remain poorly understood. While accurately measuring actual striking force is essential for performance evaluation, practical and safety challenges prevent direct measurement on athletes. The protector’s attenuation obscures the true impact, necessitating a method to estimate the original force from the attenuated data.

Methods: A controllable pendulum-based impact testing apparatus was developed to evaluate force attenuation characteristics of Taekwondo body protectors. The system delivered repeatable impacts across varying magnitudes and contact durations to a mannequin equipped with a protector. Simultaneous measurements of input and transmitted forces through the protector enabled quantification of attenuation ratios under controlled conditions. To demonstrate practical application, five Taekwondo athletes performed standardized kicks on the instrumented protector setup, allowing estimation of their actual striking forces using the derived attenuation factor.

Results: Force attenuation ratios demonstrated high consistency across impact magnitudes ranging from 300 to 5800 Newtons, with impact duration variations showing minimal influence on attenuation performance. Linear attenuation relationships were established between input and transmitted forces (R2≥0.987), enabling derivation of a predictive attenuation factor. Validation testing with the pendulum system showed that the estimated input force trajectories achieved an nRMSE of 3.5%. Averaged across the entire force range, the MAPE was 4.7% for maximum force, 1.4% for impact duration, and 3.5% for impulse. Applying the attenuation factor to standardized kicks performed by five Taekwondo athletes yielded estimated maximum striking forces ranging from approximately 1300 to 1800 Newtons.

Conclusion: This study establishes the first quantitative characterization of impact attenuation in Taekwondo body protectors, providing a validated attenuation factor for estimating striking forces from transmitted forces. These findings demonstrate a practical methodology for quantifying striking forces that are otherwise difficult to measure.