# Reproducibility and Accuracy of a New Method for Measuring the Range of Dart-Throwing Motion

## TL;DR

This study evaluates a new method for measuring dart-throwing motion range, finding it reliable and accurate with minimal bias.

## Contribution

A novel, reproducible method for measuring dart-throwing motion using a bubble inclinometer and repeated trials.

## Key findings

- Intra-class correlation coefficients showed moderate to good reproducibility for both dominant and non-dominant sides.
- Measurement reproducibility improved with increased number of trials.
- Bland–Altman analysis revealed proportional bias of 30.7% to 35.9% compared to motion capture as gold standard.

## Abstract

To evaluate the reproducibility and the accuracy of our technique to measure the range of dart-throwing motion.

Two raters measured the range of dart-throwing motion of 42 healthy participants. The participants performed a simulated hammering action with a wooden mallet, and the inclination angle of the mallet on the vertical plane was measured using an attached bubble inclinometer at the maximal position of radial extension and ulnar flexion. The sum of these angles was defined as the range of the dart-throwing motion. Each rater performed three measurement trials for each participant. To determine inter-rater reproducibility, intra-class correlation coefficients were calculated for the value of one trial, mean value of two trials, and mean value of three trials. In the first test session, wrist kinematics during measurement was recorded simultaneously using a three-dimensional optical motion capture system.

Intra-class correlation coefficients for the dominant and nondominant sides ranged from 0.67 to 0.75 and 0.68 to 0.79, respectively. The reproducibility of the measurements was improved by adopting the mean value as the number of repetitions of the measurements increased. Bland–Altman analysis revealed that our measurement contained a proportional bias of 30.7% to 35.9% compared with the values of the motion capture analysis as the gold standard.

The reproducibility of the measurements was either good or moderate. The revealed biases can provide valuable data for estimating the true range of wrist motion.

Our technique would be useful for reliable measurement of the range of dart-throwing motion, as it is easy to perform repeated measurements. Our method avoids observer bias even by a single examiner and can be carried out with readily available materials.