Diaphragm Contractility in Individuals with Chronic Ankle Instability

Introduction/Purpose Previous investigations have identified impaired trunk and postural stability in individuals with chronic ankle instability (CAI). The diaphragm muscle contributes to trunk and postural stability by modulating the intra-abdominal pressure. A potential mechanism that could help to explain trunk and postural stability deficits may be related to altered diaphragm function due to supraspinal sensorimotor changes with CAI. The purpose of this study was to examine the diaphragm contractility in individuals with CAI and healthy controls. Methods Twenty-seven participants with self-reported CAI and 28 healthy control participants volunteered. A portable ultrasound unit was used to visualize and measure the right and left hemidiaphragm thickness at the end of resting inspiration and expiration in supine while breathing quietly. The diaphragm movement was imaged and recorded on B-mode ultrasonography. The degree of diaphragm contractility was calculated from the mean of three images from the end of resting inspiration and expiration. Independent t-tests were used to compare the degree of diaphragm thickness of right and left sides between the CAI and the control groups. Results The CAI group had a smaller degree of left hemidiaphragm contractility compared with the control group (P = 0.03). There was no between-group difference in other diaphragm variables. Conclusion Individuals with CAI appear to have altered diaphragm contractility, which may be an illustration of diaphragm dysfunction and central nervous system changes in CAI population. The association between CAI and altered diaphragm contractility provides clinicians a more comprehensive awareness of proximal impairments associated with CAI. Future investigation is needed to determine whether altered contractility of the diaphragm contributes to functional impairments, activity limitations, and participant restrictions commonly observed in patients with CAI.