Objective. This study aimed to describe the interrater and intrarater reliability of the flexicurve index, flexicurve angle, and manual inclinometer in swimmers. A secondary objective was to determine the level of agreement between the inclinometer angle and the flexicurve angle and to provide an equation to approximate one angle from the other. Methods. Thirty swimmers participated. Thoracic kyphosis was measured using the flexicurve and the manual inclinometer. Intraclass correlation coefficient, 95% confidence interval, and standard error of measurement were computed. Results. The flexicurve angle and index showed excellent intrarater (ICC = 0.94) and good interrater (ICC = 0.86) reliability. The inclinometer demonstrated excellent intrarater (ICC = 0.92) and interrater (ICC = 0.90) reliability. The flexicurve angle was systematically smaller and correlated poorly with the inclinometer angle ( ). The following equations can be used for approximate conversions: flexicurve angle = (0.275 × inclinometer angle) + 8.478; inclinometer angle = (1.396 × flexicurve angle) + 8.694. Conclusion. The inclinometer and flexicurve are both reliable instruments for thoracic kyphosis measurement in swimmers. Although the flexicurve and inclinometer angles are not directly comparable, the approximate conversion factors provided will permit translation of flexicurve angle to inclinometer angle and vice versa. 1. Introduction Thoracic kyphosis is the sagittal plane curvature between the T1 and T12 vertebral bodies [1]. Normal thoracic kyphosis ranges from 20° to 50° when assessed radiographically [2] and nonradiographically [2–4]. Excessive thoracic kyphosis, defined as a kyphosis > 50° [2, 5], has been linked with a range of musculoskeletal complaints including shoulder pain [6] and cervical pain [7–9]. Previous research has consistently reported high incidences of shoulder pain in competitive swimmers, with rates of 53% [10], 54% [11], and 80% [12] amongst those documented. The increased thoracic kyphosis of swimmers is a postural adaptation to altered spinal forces experienced in swim training [13] and is proposed as being a large contributing factor to the development of shoulder pain [14, 15]. The simple and safe assessment of thoracic kyphosis is therefore of value to physiotherapists involved in treating high-level swimmers. The gold standard for the measurement of thoracic kyphosis is a radiograph, which provides a Cobb angle [16, 17]. While this method is noted to reveal the true position of the vertebrae [18], it is not always accessible in a clinical setting,
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