Introduction:
This study aimed to establish normative values for stiffness, tone, and elasticity of lower extremity muscles and to determine age and sex differences.

Methods:
Overall, 389 participants (199 females, 190 males) were included. The mechanical properties of the tibialis anterior (TA), rectus femoris (RF), vastus lateralis (VL), vastus medialis obliquus (VMO), gastrocnemius lateralis (GL), and gastrocnemius medialis (GM) muscles were assessed bilaterally with the MyotonPRO device. The data were compared with respect to sex and age.

Results:
The mechanical properties were significantly higher bilaterally in males than females in all parameters (p < 0.05). Right TA stiffness and elasticity, GM tone and stiffness were higher than left in females (p < 0.05). Greater VMO elasticity and RF tone were found in left vs. right (p < 0.05). Right GL-VL stiffness and elasticity were greater than left in males (p < 0.05). VMO-RF tones were bigger in left compared with right (p < 0.05). Among age groups, right-left TA tone and stiffness were greater in group 1 (18–28 years old) (p < 0.05). Right-left VL-VMO tones, and left RF stiffness and tone were lower in group 2 (29–39 years old) (p < 0.05). Right GM-VMO stiffness, right-left TA-GL-GM-VMO and RF elasticity were greater in group 3 (40–50 years old) compared with others (p < 0.05).

Conclusions:
The mechanical properties of leg muscles were bilaterally higher in males. Different characteristics were observed of different muscles for both sexes. GL-GM-VMO-RF elasticity decreased, and TA stiffness and VMO tone increased with advancing age in both legs