The purpose of this study was to evaluate the test-retest reliability of Closed Kinetic Chain Upper Extremity Stability Test- CKCUES test scores. Results showed excellent values of ICC for intersession reliability of number of touches score. Intrasession reliability of test also showed excellent (ICC ≥ 0.75) values scores for all samples. The results support the reliability of CKCUES Test as a complementary outcome measure for evaluating shoulder functional condition in healthy sedentary, healthy active and SIS subjects.
Results of intrasession reliability of this research are in accordance to Goldbeck & Davies, the only study found in the literature about CKCUES Test reliability. However, Goldbeck & Davies assessed just reliability of number of touches score in a sample of male recreational athletes. Moreover, there were not found studies about CKCUES Test reliability in females, sedentary subjects and in a sample with shoulder injury. Thus, some results of this study were not possible to be compared with other researches.
There was found in the literature other research that has determined reliability of other closed kinetic chain performance tests for upper extremity, with excellent values of test-retest reliability . However, that research also has not evaluated subjects with shoulder dysfunctions or injuries. Moreover, that test includes an equipment to sample quantitative data. Thus, we believe our results could be important for sportive and clinical assessment for two reasons. First because CKCUES Test is a low cost test with no need of an equipment to measure the scores, and second because the reliability of the test was determined for samples with different levels of physical conditioning and also in sample with SIS. Thus, we believe clinicians and athletic trainers can choice this test to first evaluations and to follow-ups of upper extremity performance.
Number of touches and normalized score values obtained in this research were greater than the reference values for CKCUES Test . However, it is important to consider that from the original reference there is not a range of values, but only a unique value for each score that could be considered as reference. Thus if a person has his/her score lower than reference values, scores of test can be improved. Otherwise, if scores are greater than references values, a comparison of those score could be done before and after a specific training as parameter of evaluation. Anthropometric characteristics of samples could have influenced these results, mainly because height and weight are used in the formulas for calculating normalized score and power score, respectively.
A possible justification regarding wider confidence interval of intersession reliability values of ICC of recreational athletic samples and SIS samples for all scores could be the variability of weight and height among subjects at the same group. Despite the excellent reliability for number of touches, it is important to consider that power and normalized score are dependent of the subject’s anthropometric variable. As adults composed the samples those variations is more likely to be from their body weight changes.
Moreover, considering the difference in the subject’s wingspan, i.e. the distance between fingertip to fingertip of middle fingers with the arms spread, the fact of this test consider a unique value of 36-inches (91,44 cm) distance between hands, independent of subject’s height , could limit the comparisons of performance among subjects. For example, a taller person could perform the test faster than one smaller due the larger wingspan, which could result in a greater score of number of touches, and consequently, in a greater value of normalized score and power score. Thus, when normalized score and power score are analyzed, anthropometric variables are considered in the score estimates.
On the other hand, there is another possibility to diminish the influence from the anthropometric characteristics of the subject’s height on the number of touches score by setting the distance between hands as a percentage of the total size of the subject’s wingspan or as a distance between scapular acromions. However, further studies are necessary to analyze if those changes in the CKC test are feasible, create reliable scores and safety biomechanics for patients with shoulder dysfunctions.
To date, no studies analyzing the SEM and MDC of scores of CKCUES Test were found. However, it is important to have knowledge about what is the minimal difference in the scores of an evaluation tool between revaluation sessions that could be considered as a real improvement with no error [13, 14]. Thus, our results could guide clinicians and athletic trainers with these values for subjects with and without SIS and with different levels of physical activity lifestyle.
Considering values of SEM and MDC for females groups, changes between sessions could be considered as a true change when number of touches score exceeds 4 touches for a sedentary, 4 touches for a active and 3 for a SIS person. In groups of males, changes between sessions could be considered as a true change when number of touches score exceeds 2 touches for a sedentary, 3 for active and 3 for a SIS person. With those number of touches changes, normalized score and power score also will be changed. Thus, those number of touches values could be considered as the minimal change between CKCUES Test evaluations that could be considered as a real change of improvement.
Some healthy subjects reported shoulder pain after test, even with no pain reporting before the test. A possible justification could be the fact that CKCUES Test is a high level performance test, which can cause a high demand over shoulders. Lastly, based on reliability results from samples with SIS, shoulder pain was not an impediment to those subjects performs the test, independently of rating level. In samples with SIS, a greater level of pain post test compared to pre test was expected before by the same justification. Thus, clinicians should have care when the test is considered in the initial clinical evaluation of a subject with shoulder injury. Care also should be taken when the test is being performed. If a subject shows an incorrect body positioning or some compensatory movements, or if the subject report pain during the test, an interruption might be necessary, since the axial load applied to the arm 90 degrees elevate in anterior flexion is close to body weight when the subject is touching hands in the end of the swing phase.
Results showed that CKCUES Test is a reliable tool to evaluate upper extremity function in sedentary and young male or female recreationally active subjects and also in subjects with SIS. However, this study has some limitations, such as subjects without shoulder injury are from a young population, elite athletes were not included, and only with SIS participants represented shoulder dysfunction in our sample. This way, the results of this study should be carefully analyzed when extended to other populations.