Fumio Ohtsuki

Secular changes in relative leg length in post-war Japan

Longitudinal secular changes of height and estimated leg length (ELL) or subischial leg length of Japanese boys and girls were investigated using data published in “The Statistical Report of the School Health Survey” of the Ministry of Education, Science, Sports and Culture, Japan. A significant trend towards greater relative leg length (long‐leggedness) among Japanese children and youth has occurred during the period of about four decades covered by this study. After showing a strikingly consistent trend at all age levels between 6 and 17 years and a dramatic trend during the birth‐year age period 1943–1963, the relative growth in leg length has been rapidly slowing or has stopped in both sexes. The relative growth of ELL seemed to be fixed after 11 years in boys and 9 years in girls. Maximum increment ages (MIA), both in height and ELL, were used as estimates of the timing of maximum growth during the adolescent spurt. Regression analysis was used to demonstrate the overall trend patterns of MIA in height and ELL. After removing autocorrelation effects, MIA for height is accelerated by 0.03 year in both sexes, while the MIA in ELL is accelerated by 0.03 year in boys and 0.01 year in girls. Thus, MIA in ELL in girls is occurring earlier but to a smaller extent than in boys. The average maturity difference between boys and girls is 2.07 years in height, but 2.83 years in lower extremity length. Am. J. Hum. Biol. 12:405–416, 2000.

The vertebral curvature of sportsmen

To characterize the vertebral curvature of individuals from a variety of sporting backgrounds, 380 Japanese males were categorized into 11 groups based on sport participation: rugby, soccer, kendo, swimming, sailing, four track and field events (sprinting, distance running, jumping and throwing), bodybuilding and no athletic engagement. The vertebral curvature of each subject was estimated from a Moire photograph. The vertebral curvature lines of the 11 groups were compared and classified into four types based on the shape of the vertebral curvature: (1) bodybuilders and swimmers; (2) rugby players, sailors, soccer players and non-athletes; (3) kendo participants, middle- and long-distance runners and sprinters; (4) throwers. The relationship between the shape of the vertebral curvature and the characteristics of the sport was determined. We found that posture was specific to the sport. Sprinters, middle- and long-distance runners, jumpers, kendo participants and throwers had a deeply curved vertebral col...

Secular trends for takeoff and maximum adolescent growth for eight decades of Japanese cohort data.

The presence of secular trends in the onset or takeoff of the adolescent growth spurt and subsequent adolescent growth of Japanese boys and girls were investigated using data published in “The Statistical Report of the School Health Survey” by the Ministry of Education, Science, Sports and Culture, Japan. An optimum kernel regression method was used to derive the biological parameters of the adolescent growth curve. An increasing trend in height at takeoff (i.e., height at the onset of the adolescent growth spurt) and height at peak height velocity (PHV) among Japanese children was evident during the 8 decades covered in this study. Age at PHV (i.e., the timing of the maximum adolescent growth) for each sex has decreased. Age at takeoff (i.e., the timing of the onset of the adolescent growth spurt) has decreased in boys during this century, but was almost constant in girls at about 7.8 years of age. Moreover, the interval between age at takeoff and age at PHV in girls has gradually decreased over this century. Since the birth year 1915, velocity at takeoff for girls was markedly greater than that for boys, whereas peak height velocity for girls was significantly less than that for boys (P < 0.05). Am. J. Hum. Biol. 12:702–712, 2000.

Estimation of maximum increment age in height and weight during adolescence and the effect of World War II.

An attempt was made to estimate the maximum increment age (MIA) in height and weight of Japanese boys and girls during the birth years 1893–1990 through the published data of the Ministry of Education, Science, Sports and Culture in Japan. In cases where the same maximum annual increment occurred in two or three successive age classes in a birth year cohort, a new formula (see Eq. 2) was developed to estimate the MIA. The existing formula for estimating MIA was modified to remove the mathematical deficiency (Eq. 1). Estimated MIA shows an overall declining trend, except in birth year cohorts 1934–1951. The effect of World War II on MIA was investigated by a dummy variable regression model. On average, during the birth years 1934–1951, MIA in height decelerated by 1.35 years in boys and 0.54 year in girls, while MIA in weight decelerated by 0.95 year in boys and 0.78 year in girls. Am. J. Hum. Biol. 12:363–370, 2000.