Echo intensity is weakly associated with muscular strength and endurance in young, healthy adults.

The purpose of this study was to evaluate the relationships between echo intensity (EI) and muscular strength (maximal voluntary isometric contraction [MVIC]) and endurance (time-to task-failure [TTF]) in young adults. Ultrasonography was used to examine the dominant vastus lateralis of 15 young men and 15 young women. The participants completed an MVIC to assess muscular strength and sustained a bilateral, leg extension at 45% MVIC to assess muscular endurance. There was a significant (r = -0.354, p = 0.028) correlation between EI and normalized MVIC force for the combined sample (n = 30). There was also a significant (r = -0.520, p = 0.002) correlation between EI and absolute MVIC force for the combined sample. The correlation between EI and TTE was significant for the men (r = -0.449, p = 0.047) and the combined sample (r = -0.477, p = 0.004). Overall, muscle quality as assessed by EI does not appear to be strongly related to muscular strength, but there may be a modest correlation with muscular endurance.