Test-retest reliability of a newly developed instrument for measurement of force production and speed in closed kinetic chain for upper extremity : Measurements on a group of athletes with cerebral palsy and a reference group

Abstract: Aim and research questions: The aim of this master thesis was to test for test-retest reliability for a newly developed force instrument (FI) and determine if a combined effect of trial, speed and resistance exist on the variable fraction effective force (FEF) for a group of athletes with cerebral palsy (CP-group) and a reference group (AB-group).  1. What is the intraclass correlation coefficient on maximum velocity measured on two occasions with the FI for a CP-group and an AB-group? 2. What is the intraclass correlation coefficient on FEF for a flexion movement measured on two occasions for an AB-group? 3. Is there an interaction effect of; a) trial and group, b) trial, speed and group, c) trial, resistance and group and d) trial, speed, resistance and group, on the variable FEF for a flexion movement for a CP-group and an AB-group?   Method: This master thesis was an experimental cross-sectional study with a test-retest design. Data collection took place in Stockholm and in Elche (Spain), 2022. Participants visited the BMC laboratory at two occasions. Participants completed tasks with their least impaired arm (CP-group) or dominant arm (AB-group) in a horizonal movement at different resistances and speeds on the FI. Maximum velocity together with force in 3 directions was registered. FEF was calculated from the three forces. ICC on Vmax for both groups and FEF for the AB-group was conducted together with a mixed-design ANOVA on de independent variables trial, group, speed and resistance on the dependent variable FEF.    Results: 18 participants in the CP-group and 20 participants in the AB-group was included for statistical analysis. The ICC on Vmax was .944 for the CP-group and .804 for the AB-group. The mean ICC for FEF was .644 for the AB-group. Using a mixed-design ANOVA concluded that there was no significant interaction effect on trial, group, speed and resistance, F(4) =2.069, p=.088, nor in any of the other combinations.    Conclusion: The newly developed FI shows good test-retest reliability for both groups and could be used for measurements of arm coordination. Further studies are needed to further evaluate reliability of the instrument.