Reliability of ultrasonographic measurement of the architecture of the vastus lateralis and gastrocnemius medialis muscles in older adults

Objective: To determine the test-retest reliability of measurements of thickness, fascicle length (L f) and pennation angle (8) of the vastus lateralis (VL) and gastrocnemius medialis (GM) muscles in older adults. Participants: Twenty-one healthy older adults (11 men and ten women; average age 68·1±5·2years) participated in this study. Methods: Ultrasound images (probe frequency 10MHz) of the VL at two sites (VL site 1 and 2) were obtained with participants seated with knee at 90 o flexion. For GM measures, participants lay prone with ankle fixed at 15 o dorsiflexion. Measures were taken on two separate occasions, 7days apart (T1 and T2). Results: The ICCs (95% CI) were: VL site 1 thickness=0·96(0·90-0·98); VL site 2 thickness=0·96(0·90-0·98), VL ?=0·87(0·68-0·95), VL L f=0·80(0·50-0·92), GM thickness=0·97(0·92-0·99), GM ?=0·85(0·62-0·94) and GM L f=0·90(0·75-0·96). The 95% ratio limits of agreement (LOAs) for all measures, calculated by multiplying the standard deviation of the ratio of the results between T1 and T2 by 1·96, ranged from 10·59 to 38·01%. Conclusion: The ability of these tests to determine a real change in VL and GM muscle architecture is good on a group level but problematic on an individual level as the relatively large 95% ratio LOAs in the current study may encompass the changes in architecture observed in other training studies. Therefore, the current findings suggest that B-mode ultrasonography can be used with confidence by researchers when investigating changes in muscle architecture in groups of older adults, but its use is limited in showing changes in individuals over time.