Abstract Background There is a lack of of cross-sectional research that has investigated muscle morphology, function, and functional capability in all age-bands of healthy adults. The primary aim of this study was to evaluate age-related differences in indices of vastus lateralis (VL) muscle morphology, function and functional capability in a sample of healthy males and females aged 18-70yrs. Secondary aims were to evaluate relationships between age and VL muscle morphology and function and functional capability. Methods B mode Ultrasonography and Tensiomyography were used to measure VL muscle thickness, pennation angle, fascicle length, and contractile properties in 274 healthy adults aged 18-70yrs. Measurements of grip strength and functional capability (1-min chair rise test) were also taken. Data analysis included descriptive statistics, correlations, one-way ANOVAs, and multiple regressions. Results Negative correlations were found between age and muscle thickness (rs = -.56), pennation angle (rs = -.50), fascicle length (rs = -.30), maximal displacement (rs = -.24), grip strength (rs = -.27) and the 1-min chair rise test (rs = -.32). Positive correlations were observed between age and the echo intensity of the muscle (rs = .40) and total contraction time (rs = .20). Differences in the indices of muscle health were noticeable between the 18–29 age band and the 50–59 and 60–70 age bands (p