A Cross-Sectional Study of Gastrocnemius Medialis Muscle Fascicle Length and Anatomical Cross-Sectional Area in 8-to 18-Year-Old Female Volleyball Athletes

This cross-sectional study examined gastrocnemius medialis fascicle length (FL) and anatomical cross-sectional area (ACSA) in female volleyball athletes aged 8-18 years, in an attempt to investigate morphological growth changes during childhood and adolescence. Methods: Eighty-nine athletes were assigned to five groups: 8-10, 10-12, 12-14, 14-16 and 16-18 years old. Height, body mass, leg and calf length were measured, and maturity offset was calculated from anthropometrics. FL and ACSA were assessed using ultrasonography. Results: FL was longer and ACSA was larger in the 12-14 y group compared with the 8-10 y group (4.31 +/- 0.60 vs. 3.66 +/- 0.40 cm, p = 0.008 and 13.08 +/- 3.01 cm(2) vs. 9.98 +/- 2.07 cm(2), p = 0.018, respectively). However, there were no differences in FL or ACSA among the groups aged between 12 and 18 years (p > 0.573 and p > 0.352). Notably the percentage increase in ACSA between the youngest (8-10 y) and the oldest group (16-18 y) was twofold greater than the percentage increase in FL (49% vs. 24%). Significant correlations were found between anthropometric characteristics FL and ACSA (r = 0.366-760, p < 0.001). Conclusions: These data indicate that there is a rapid increase in FL and ACSA from the age of 8 y until the age of 14 y, which is a crucial time frame for muscle growth.