Concurrent Validity and Reliability of Ultrasound-based Muscle Thickness and Inclinometer-based Range of Motion Measurements in Assessing Stretching-induced Changes in Muscle Flexibility in Healthy Adults

Background: Muscle thickness (MT) measurement using ultrasound image is emerging as a useful method to assess muscle mass during stretching. Traditionally, range of motion (ROM) measurements assessed by digital inclinometer are considered reliable and valid parameter for monitoring muscle flexibility. The ultrasound-based measurement for MT to monitor muscle flexibility has yet to be validated. Objects: This study aimed to determine whether ultrasound measurement can serve as a valid alternative to a digital inclinometer for assessing muscle flexibility following stretching interventions. Methods: A randomized crossover design study was conducted with 20 healthy young participants. The stretching exercise program was carried out passive static and hold-relax proprioceptive neuromuscular facilitation stretching exercises applied on gastrocnemius-soleus muscle group with 3 times a week for 2 weeks. Data were collected 3 times for pre- and post-tests. Dorsiflexion ROM was measured by a digital inclinometer and the MT of gastrocnemius muscle by the ultrasound. Intraclass correlation coefficient (ICC) analysis for test-retest reliability, Wilcoxon sign rank test for stretching effects, and Spearman’s correlation analysis for determining the concurrent validity of two measurements. Results: ICC values of pre- and post-tests in both ROM and MT measurements were showed good to excellent intra rater reliabilities ranging from 0.782 to 0.968 (p < 0.001). A significant increase in the ROM measurements was observed following the stretching program (p < 0.01), whereas no significant change in the MT measurement was showed. Spearman’s correlations revealed weak relationships between the ROM and MT measurements (r = –0.217 for pre-test, r = –0.259 for post-test, r = –0.282, p < 0.05 for changes). Conclusion: These findings suggest that both the MT and ROM measurements were not compatible for monitoring muscle flexibility following stretching exercises regardless of their good reliabilities. Further investigations may be required to the MT measurement alone to be an alternative method. 키워드1 (원어) Muscle flexibility, Proprioceptive neuromuscular facilitation, Static stretching, Ultrasound imaging