Abstract
Background Adequate muscle strength, power, and endurance are important in children's daily activities and sports. Various instruments have been developed for the assessment of muscle function; each measures different aspects. The Functional Strength Measurement (FSM) was developed to measure performance in activities in which strength is required.
Objective The study objective was to establish the test-retest reliability and structural and construct validity of the FSM.
Design A cross-sectional descriptive study was conducted.
Methods The performance of 474 children with typical development on the FSM was examined. Test-retest reliability (n=47) was calculated with the intraclass correlation coefficient (2.1A) for agreement. Structural validity was examined with exploratory factor analysis, and internal consistency was established with the Cronbach alpha. Construct validity was determined by calculating correlations between FSM scores and scores obtained with a handheld dynamometer (HHD) (n=252) (convergent validity) and between FSM scores and scores on the Movement Assessment Battery for Children–2 (MABC-2) (n=77) (discriminant validity).
Results The test-retest reliability of the FSM total score ranged from .91 to .94. The structural validity revealed one dimension, containing all 8 FSM items. The Cronbach alpha was .74. The convergent validity with the HHD ranged from .42 to .74. The discriminant validity with MABC-2 items revealed correlations that were generally lower than .39, and most of the correlations were not significant. Exploratory factor analysis of a combined data set (FSM, HHD, and MABC-2; n=77) revealed 2 factors: muscle strength/power and muscle endurance with an agility component.
Limitations Discriminant validity was measured only in children aged 4 to 6 years.
Conclusions The FSM, a norm-referenced test for measuring functional strength in children aged 4 to 10 years, has good test-retest reliability and good construct validity.
Footnotes
Mrs Aertssen and Professor Smits-Engelsman provided concept/idea/research design, data analysis, project management, participants, and facilities/equipment. All authors provided writing. Mrs Aertssen provided data collection. Professor Smits-Engelsman provided institutional liaisons and consultation (including review of manuscript before submission). The authors thank all of the schools, children, and parents for participating in this study and the students of AvansPlus for their help with collecting the data.
The study was approved by the Dutch Medical Ethics Committee (CCMO).
- Received January 20, 2014.
- Accepted November 5, 2015.
- © 2016 American Physical Therapy Association
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