The objective of this study was to examine biological growth and development in skating performance by focusing on thigh muscle thickness and anaerobic power output capacity in Japanese speed skaters. One hundred thirty-three male and 96 female skaters aged from 10 to 22 years old were tested in this study. The anterior (MTA) and posterior (MTP) thicknesses of the thigh muscles were measured by the B-mode ultrasonic method. Maximal anaerobic power output capacity (MAP) was determined using a bicycle ergometer. The mean 500 m skating velocity (SV), calculated from recently attained individual best times, was used as a measure of skating performance. These parameters, along with height, were plotted on a logarithmic graph to obtain the allometric equation y=bx^a, where “a” is a growth index.There were two sharp bends in the graph showing the relationships between MTA, MTP, MAP, SV and body height in both males and females. The growth indexes “a” between the first and second changing points in all the above relationships were observed to be larger than the other phases. Ranges of body height between the first and second changing point in muscle thicknesses (MTA, MTP) ranged from 152.2-154.8 cm to 168.1-168.3 cm in males, and from 142.8-144.9 cm to 154.4-157.6 cm in females. The ranges of MAP were from 139.8 cm to 166.8 cm in males, and from 138.8 cm to 157.8 cm in females. However, the height ranges of SV were from 147.4 cm to 167.8 cm in males, and from 142.2 cm to 153.2 cm in females.From these results, it was suggested that accelerated development of skating performance and anaerobic power output capacity begins earlier than muscle structural development in speed skaters.

The purpose of this study was to examine the age- and athletic event-related differences in trunk muscularity among junior and senior athletes. The cross-sectional areas (CSAs) of the rectus abdominis, lateral abdominal muscle group, psoas major and erector spinae were determined on magnetic resonance imaging for 188 junior athletes aged 12-18 years and 164 senior athletes aged ≥ 19 years in six different athletic events (male: archery, table tennis, Nordic combined, basketball, and wrestling; female: archery, table tennis, and gymnastics). To examine the age-related differences for each athletic event and sex, the subjects were classified into the following age groups: 12-15 years, 16-18 years and senior (≥ 19 years). The main results were as follows. 1) The magnitude relationships of trunk muscle CSA/height² differed among the age groups by athletic event and muscle. 2) The values of CSA/height² of the lateral abdominal muscle group and erector spinae were significantly larger in female gymnasts aged 12-15 years than in female athletes from the other athletic events. These results respectively indicated that 1) each trunk muscle has the potential to specifically develop according to the athletic events and 2) selective hypertrophy of the trunk muscles can be induced by training reflecting athletic event-specific characteristics in female junior high school athletes.