Age- and athletic event-related differences in trunk muscularity in junior athletes: A comparison with the results for the senior athletes / 体力科学

<p>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.</p>

CROSS-SECTIONAL AREA OF PSOAS MAJOR MUSCLE IN HIGH SCHOOL ATHLETES / 体力科学

The aim of the study was to measure the cross-sectional area of the psoas major muscle (P-ACSA) in high school athletes and to produce a P-ACSA index independent of body size using an allometric modeling approach to examine the differences in gender and sport specialization. The subjects were 254 female (16.8±0.8 yrs) and 540 male (16.9±0.8 yrs) high-level high school athletes from 17 different sports. Fat-free mass (FFM) was measured by the Bod Pod system (LMI) and P-ACSA was determined by magnetic resonance imaging at the center of the L4-L5 transverse level. Since the power function model fit the data better than a simple linear model in the correlation between FFM and P-ACSA, and the power exponent parameter was almost equal to the theoretically anticipated 2/3 in both genders, the P-ACSA per FFM^2/3 as well as the absolute P-ACSA was calculated. Both of the absolute P-ACSA and P-ACSA per FFM^2/3 were significantly different according to gender and the sport specialization. While volleyball and badminton players and canoeists showed smaller P-ACSA, in accordance with the previous studies on senior sprinters, high school sprinters also showed predominant development of P-ACSA regardless of gender. These results suggested that regular involvement in sprinting activity could affect the size of the psoas major muscle in high school athletes.