Reliability and validity of ultrasound to estimate muscles: A comparison between different transducers and parameters.

BACKGROUND AND AIMS: We aimed to investigate the test-retest reliability and validity of ultrasound for two commonly used types of transducer, using different methods for the estimation of muscle size and echo intensity (EI). METHODS: Fourteen healthy adults were included in this study. Ultrasound images of the rectus femoris size (thickness in cm and cross-sectional area [CSA] in cm2), obtained at the mid-thigh, were validated against MRI. Both a linear and a curved array transducer were used to assess rectus femoris size and EI (values 0-255, higher scores indicating increased intramuscular fat and interstitial fibrous tissue). To assess test-retest reliability of ultrasound, participants were tested twice, with a one-week interval. Validity and reliability were evaluated using paired sample t-tests, intraclass correlation coefficient (ICC), and Bland-Altman plots. RESULTS: No significant differences between the repeated evaluations of rectus femoris thickness, CSA and EI were found. Reliability for thickness and CSA evaluations was excellent for both transducers (ICC = 0.87-0.97) and moderate for EI (ICC = 0.42-0.44). Mean difference between MRI and ultrasound for CSA (curved = 0.59 cm2, p = 0.086; linear = 2.1 cm2, p = 0.002) and thickness (curved = 0.31 cm, p = 0.01; linear = 0.21 cm, p = 0.043) were small but significant, except for CSA using a curved transducer. Agreement between ultrasound and MRI ranged from moderate for thickness (ICC = 0.45) to excellent for CSA (ICC = 0.92). CONCLUSIONS: Our study demonstrates that the test-retest reliability and validity of muscle size estimation by ultrasound for both curved and linear array transducers seems to be adequate. Future studies should focus on the longitudinal evaluation of muscle size and EI by ultrasound.

Validation of the Fitbit One, Garmin Vivofit and Jawbone UP activity tracker in estimation of energy expenditure during treadmill walking and running.

OBJECTIVES: To determine the validity of energy expenditure estimation made by the Fitbit One, Garmin Vivofit and Jawbone UP activity trackers during treadmill walking and running. Determining validity of such trackers will inform the interpretation of the data they generate. DESIGN: Cross-sectional study. METHOD: Fourteen adults walked at 0.70, 1.25, 1.80 ms-1 and ran at 2.22, 2.78, 3.33 ms-1 on a treadmill wearing a Fitbit One, Garmin Vivofit and Jawbone UP. Estimation of energy expenditure from each tracker was compared to measurement from indirect calorimetry (criterion). Paired t-tests, correlation coefficients and Bland-Altman plots assessed agreement and proportional bias. Mean percentage difference assessed magnitude of difference between estimated and criterion energy expenditure for each speed. RESULTS: Energy expenditure estimates from the Fitbit One and Garmin Vivofit correlated significantly (p< 0.01; r= 0.702; 0.854) with criterion across all gait speeds (0.70-3.33 ms-1). Fitbit One, Garmin Vivofit and Jawbone UP correlated significantly (p < 0.05; r = 0.729; 0.711; 0.591) with criterion across all walking speeds (0.70-1.80 ms-1). However, only the Garmin Vivofit correlated significantly (p< 0.05; r = 0.346) with energy expenditure estimations from criterion across running speeds (2.22-3.33 ms-1). Bland-Altman plots showed proportional bias for the Fitbit One and Garmin Vivofit. Energy expenditure estimations of single speeds were overestimated by the Fitbit One and underestimated by the Garmin Vivofit. CONCLUSIONS: Energy expenditure reported by the devices distinguished between walking and running, with a general increase as exercise intensity increased. However, the reported energy expenditure from these devices should be interpreted with caution, given their potential bias and error. Practical implications Although devices report the same outcome of EE estimation, they are not equivalent to each other and differ from criterion measurements during walking and running. These devices are not suitable as research measurement tools for recording precise and accurate EE estimates but may be suitable for use in interventions of behaviour change as they provide feedback to user on trends in energy expenditure. If intending to use these devices in studies where precise measurements of energy expenditure are required, researchers need to undertake specific validation and reliability studies prior to interventions and the collection of cross-sectional data.

Light physical activity is positively associated with cognitive performance in older community dwelling adults.

OBJECTIVES: To evaluate the associations between an objective measure of different intensities of physical activity, upper- and lower-limb muscle strength and psychomotor performance and set-shifting domains of cognitive executive function in older adults. DESIGN: A cross-sectional study. METHODS: From the Tasmanian Older Adult Cohort Study, 188 community-dwelling older adults (53.7% female; mean age±SD 63.98±7.3 years) undertook 7-day physical activity behaviour monitoring using an accelerometer. Dynamometers were used to assess leg extension strength. The Trail Maker Tests were used to measure psychomotor processing speed and set-shifting performance. RESULTS: When controlling for age, smoking history, alcohol intake, educational achievement and neuropsychological functioning, higher levels of light physical activity, but not sedentary behaviour or moderate or vigorous physical activity, was found to be associated with better set-shifting performance. Neither physical activity behaviour or muscle strength were found to be associated with psychomotor performance. In addition, older age, greater alcohol intake, and lower levels of educational attainment, verbal learning and memory performance were significantly associated with lower scores on the set-shifting task; whereas older age and reduced neuropsychological functioning were associated with lower psychomotor processing speed scores. CONCLUSIONS: Light physical activity is associated with higher executive functioning in community-dwelling older adults and this strengthens the evidence supporting exercise as a neuroprotective agent. Further studies are needed to understand why light physical activity behaviour positively influences executive functioning, and how such physical activity can be implemented into the daily routine of older adults.

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 (θ) 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 ± 5·2 years) participated in this study. METHODS: Ultrasound images (probe frequency 10 MHz) of the VL at two sites (VL site 1 and 2) were obtained with participants seated with knee at 90º flexion. For GM measures, participants lay prone with ankle fixed at 15º dorsiflexion. Measures were taken on two separate occasions, 7 days 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 θ = 0·87 (0·68-0·95), VL L(f) = 0·80 (0·50-0·92), GM thickness = 0·97 (0·92-0·99), GM θ = 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.