Construct Validity of the Trunk Impairment Classification System in Relation to Objective Measures of Trunk Impairment

ObjectiveTo determine the validity of the Trunk Impairment Classification system (TIC) with 4 possible scores (0, most impaired; 0.5; 1.0; 1.5, least impaired) in relation to objective, instrumented measures of impairment.DesignCross-sectional design.SettingNational wheelchair rugby and basketball competitions of The Netherlands and Belgium.ParticipantsVolunteer sample of athletes (N=34) with a minimum of 1-year experience in their sport.InterventionsStatic sitting balance tasks on a stable and unstable surface; dynamic sitting balance tasks in anterior-posterior, left-right, and oblique directions; and trunk muscle strength tasks in forward, left, right, and backward directions.Main Outcome MeasuresSway area of the center of pressure in static sitting balance, maximum excursion of center of pressure displacement in dynamic sitting balance, and maximum isometric force in trunk muscle strength.ResultsAthletes with TIC score 0 were not able to sit unsupported. The Kruskal-Wallis test showed a significant difference in trunk muscle strength (P<.001) and dynamic balance in the oblique direction forward to the left and backward to the right between the TIC scores (P=.012). Post hoc analysis showed a significant difference between TIC score 0 and the other TIC scores for trunk muscle strength in all directions. There was a significant difference between TIC score 1.5 on one hand and TIC scores 0.5 and 1.0 on the other hand for dynamic balance in the right oblique direction.ConclusionsThe TIC is a valid scale for trunk impairment, which measures neuromusculoskeletal trunk impairment, independent of the health condition causing the impairment. Additional research is needed for coordination impairment and to assess whether TIC scores 0.5 and 1.0 should continue as separate scores.