The aim of the present study was to quantify changes in human skeletal muscle pennation angle (Fθ) values during growth and adult life. The human gastrocnemius medialis muscle of 162 subjects (96 males and 66 females) in the age range 0-70 years was scanned with ultrasonography. The subjects were laying prone, at rest, with the ankle maintained at 90° with all muscles relaxed. Fθ increased monotonically starting from birth (0 years) and reached a stable value after the adolescent growth spurt. There was a significant (p<0.05) linear relationship between Fθ and muscle thickness (TK). Fθ = 0.84 (± 0.09) * TK + 3.15 (± 1.13). Human gastrocnemius medialis F θ and TK data found in the literature seem to fit the Fθ-TK plot in a coherent manner, independent of the physiological or anatomical characteristics of the subject. The present findings indicate that Fθ is not a constant parameter but evolves, as is the case for bone length and height, as a function of age.
2001 Japan Society of Physiological Anthropology