Author(s): KOKUDO, S., Institution: CHUKYO UNIVERSITY, Country: JAPAN, Abstract-ID: 1149

INTRODUCTION:
Beunen and Malina (1986) reported that 25% of boys exhibit a temporary decrease in running speed during the growth spurt period. Furthermore, Philippaerts et al. (2006) found that 30m dash speed decreased by -0.6 seconds/year 12 months before the age of peak height velocity (APHV) in junior soccer players. Kokudo (2019) indicated that there may be a temporary stagnation in running speed development and a deterioration of running movement due to adolescent awkwardness (AK) just before or after the APHV. He also highlighted the difficulty in treating the occurrence of AK as a group phenomenon due to significant individual differences in the timing of rapid developmental stages and motor skills, underscoring the necessity of meticulously tracking individual changes.
The purpose of this study was to investigate methods for clarifying the appearance of AK and the characteristics of its subsequent development. Additionally, it aimed to elucidate the process of onset and offset of AK through a case study targeting individuals who have undergone continuous training and have long-term records of height and athletic performance.
METHODS:
We hypothesized that the emergence of AK would be more likely in exercises that involve moving ones body weight, and that this feature would be more pronounced with ongoing training. The subject was a Japanese male who continuously performed the high jump from primary school until adulthood, with a final height of 180.5 cm and a best high jump record of 2.15m. Growth data were collected from school health checkup records. Due to the rarity of individuals recording all their performances, records equaling or surpassing previous personal bests and the ages at which these records were achieved were used as data. A modified BTT model, including two logistic functions with the infant growth period defined as constant, was used for growth data. For the high jump record, the BTT model, characterized by three logistic functions, was employed to analyze performance development (Bock et al., 1990).
RESULTS:
The goodness of curve fitting was R^2 = 0.999 for growth and R^2 = 0.994 for high jump performance development, indicating excellent fits. The peak height velocity (PHV) was 10.66 cm/year at age 12.25 years. Performance development speed was less than 5.0 cm/year from ages 10.9 to 12.7 years. A rapid development speed was observed shortly thereafter, from 13.0 to 13.8 years of age, reaching 126.8 cm/year at 13.4 years of age, 1.15 years after APHV. At this time, the height velocity was 6.74 cm/year, which was 63.2% of the PHV. The growth rate remained above 7 cm/year until around 17 years of age.
CONCLUSION:
The BTT model, with three combined logistic functions, adequately explained the growth in height and development of performance. In this sample, performance stagnation was observed during the period corresponding to the adolescent surge phase, but the end of the growth surge phase represented an explosive period of rapid developmental progression.