Test-retest reliability of a novel unilateral thoracic expansion measurement using stretchable strain sensors

[Purpose] We report here a new method for measuring unilateral thoracic expansion using stretchable strain sensors. In this study, we assessed the test-retest reliability of this method and compared left and right thoracic expansions in healthy males. [Participants and Methods] Thirty healthy males (mean age, 30.1 ± 7.4 years) participated in this study. Two strain sensors were placed on the lateral walls of the thorax at xiphoid process level. Participants were asked to take three deep breaths, and the change in sensor length from the position at maximal expiration to that at maximal inspiration was recorded. These measurements were simultaneously performed on left and right sides. Unilateral thoracic expansions were calculated to assess differences between the maximal expiratory and inspiratory positions for each deep breath. The test-retest reliability of the unilateral thoracic expansion was then examined. [Results] Test reliability was excellent for both first and second datasets. Retest reliability was also excellent. The minimum detectable change (MDC) in the retest was 3.31 mm. [Conclusion] This newly developed method for measuring thoracic expansion is sufficiently reliable. No differences in thoracic expansion were observed between left and right sides in healthy males.