Application of ultrasound elastography in the evaluation of muscle strength in a healthy population.

Background: To investigate the validity of shear wave elastography (SWE) for the evaluation of muscle strength compared with isokinetic muscle testing, and to assess the influence of demographic factors such as height, weight, and body mass index (BMI) on the shear wave velocity (SWV).

Methods: Sixty healthy volunteers were consecutively enrolled. SWE was used to measure the SWV of the right quadriceps femoris in a relaxed position, in a tensive position, and under loads of 1 and 2 kg. Muscle strength parameters including peak torque (PT), PT to body weight ratio (PT/BW), and total work (TW) were evaluated using isokinetic muscle testing. The SWV of the rectus femoris in different positions were compared using the Friedman test and the Kruskal-Wallis test, and the SWV and muscle strength parameters were compared between different genders and age groups using the Mann-Whitney U test. Additionally, Spearman's correlation coefficient was used to evaluate the correlation between SWV and muscle strength, as well as the possible effects of height, weight, and BMI on SWV.

Results: As the load increased, the SWV of the rectus femoris increased (P<0.001). In the relaxed position, there was no significant correlation between the SWV and the results of isokinetic muscle testing. With increasing load, the SWV and the results of isokinetic muscle testing were not significantly correlated (r=-0.256--0.392, P<0.05). In the 1 kg load position, height and weight were not significantly correlated with SWV (r=-0.261--0.393, P<0.05). In the relaxed position, there were no significant differences in the maximum, minimum, or mean SWV of the rectus femoris between different genders and age groups (P>0.05). However, under a 1 kg load, the maximum, minimum, and mean SWV of the females in this study were significantly higher than those of the males (4.49±0.60 3.98±0.68 m/s; 2.55±0.61 2.20±0.63 m/s; and 3.51±0.60 3.06±0.58 m/s; P=0.003, 0.028, and 0.004, respectively). Furthermore, there were significant differences in the maximum and mean velocities between the groups aged 20-34 and 35-60 years (4.11±0.62 4.47±0.70 m/s; 3.17±0.53 3.52±0.69 m/s; P=0.045 and 0.044, respectively).

Conclusions: Ultrasound elastography (UE) shows potential for the measurement of muscle strength. The SWV of muscles demonstrate an increasing trend with the increase of impedance. Additionally, age and gender have a significant effect on SWV, while the effects of height, weight, and BMI require further investigation.