The responsiveness of muscle strength tests in adults with intellectual disabilities

Background Muscle strength is both a strong predictor for future negative health outcomes and a prerequisite for physical fitness and daily functioning of adults with ID. Therefore, it is important to be able to monitor the muscle strength of adults with ID over time. The aim of this study is to assess the responsiveness of five field tests that measure muscle strength and endurance (grip strength, hand-held dynamometry of leg extension and arm flexion, 10RM-test of the seated squat and the biceps curl, 30-s chair stand and the 5-times Chair stand) in adults with ID after a 24-week resistance-exercise training (RT) programme. Method The responsiveness of the five muscle strength and endurance tests was assessed by correlating the change scores of the five tests with the slope of the training progression of specific exercises within the RT-programme, namely, the step up, seated squat, biceps curl and triceps curl. Results The 10RM-test of the seated squat was significantly correlated with the step up (R = 0.53, P = 0.02) and the seated squat (R = 0.70 P = 0.00). None of change scores on the other tests was significantly correlated with the training progression of the exercises. Conclusion The 10RM test of the seated squat could potentially be used to evaluate the effects of an RT-programme in adults with ID. Responsiveness of the grip strength, hand held dynamometry, 10RM-test of the biceps curl, 30-s chair stand and the 5-times chair stand could not yet be confirmed.