# A New Flexometric Method to Evaluate Range of Movement: A Validity and Reliability Study
###### Abstract  
Hip range of movement (ROM) impairments could affect individuals' quality of life. The aim of this study is to describe a new flexometric method (FM) as a means to estimate hip ROM and to determine its concurrent validity and inter-rater and intra-rater reliability. Hip ROM was measured by performing the straight leg raise test (SLR) and hip abduction test (HA). The WIMU system is the gold standard. ROM was calculated in degrees using a trigonometric function based on values derived from measurements with a flexometer. The SLR and the HA showed high concurrent validity and good inter- and intra-rater reliability with an interclass correlation coefficient value that was at all times > 0.9. The minimal detectable change at the 90% confidence level for inter- and intra-rater reliability was equal to or greater than 5.7\({}^{\circ}\) in SLR-Right, 5.6\({}^{\circ}\) in SLR-Left, 5.1\({}^{\circ}\) in HA, 6.3\({}^{\circ}\) in SLR-Right, 4.9\({}^{\circ}\) in SLR-Left, and 5.4\({}^{\circ}\) in HA, respectively. This study suggests that the FM is a valid and reliable tool for assessing hip ROM. Due to its convenience and cost-effectiveness, this method could be widely used to measure the ROM of several joints in field-based tests.  
straight leg raise test; hip abduction test; flexometric method; tape measure method +
Footnote †: journal:  
0000-0001-9993-3399-3399-3399-3399-3399-39 given its high validity and reliability as a measure of ROM, the WIMU system (WI) is often used as the gold standard [19]. To assess the ROM, measurements of hip flexion, extension, abduction, adduction, and internal and external rotation can be performed using a goniometer [20]. This provides insights into joint mobility and potential limitations. Additionally, techniques for evaluating the range of motion in the hip and knee joints, as well as the length and flexibility of associated muscles, include the prone hip extension test, the Thomas test, the knee extension test, the Ober test, the modified Ober test, the gastrocnemius muscle length test, the straight leg raise test, and the abduction test [21]. The universal goniometer remains the most documented device for measuring ROM in these tests [22], although the reliability of the goniometric technique may be reduced when measuring hip ROM and may be highly variable depending on the movement assessed [23]. However, physical trainers and coaches commonly prioritize the capability to conduct widely accessible, cost-effective, and minimally invasive tests for analyzing athletes' performance [13; 24]. In this regard, field-based tests are generally used. Such tests are useful for measuring the distance between bony anatomical landmarks with a TM in centimeters [25; 26]. Although the tape measure method (TMM) is currently being used, non-negligible effects of individual differences in leg, trunk, and arm lengths and anatomical diameter are difficult to be considered by this method. Moreover, these differences between subjects frequently have a negative impact on the validity of the test scores [26; 27]. Several studies have assessed hip ROM by combining TM with trigonometric principles to provide reliable measures of joint angles [28; 29; 30; 31], yet no studies have found valid measures to avoid individual anthropometrical differences.  
As a consequence of the TMM's limitations, the aims of this study are (i) to propose a trigonometric equation that uses values obtained from the tape measurements of the flexometric method (FM) to assess the ROM from field-based tests and (ii) to assess the concurrent validity and intra- and inter-rater reliability when applied to the right and left straight leg raise test (SLR) and the hip abduction test (HA).