From analysis of 10 years of data from the MEXT New Physical Fitness Test, we derived an answer to when physical fitness training should begin.
The current proposals using the Miyashita Model are based on 30 year-old data, and need to be substantially updated.
1) The current model's optimal time for physical fitness development is too late； following this model will result in missing the optimal period for training.
2) There is a large difference in the optimal training period between sexes. It is necessary to propose different models for boys and girls.
3) There is large potential for physical development in early childhood. Especially in endurance, agility, flexibility, etc., the optimal training period may occur during early childhood.
4) For strength training, the optimal age for boys is 12.6 years old, with a range of 10.6-14.9 years old. For girls, the optimal age is 10.6, with a range from 7.65-13.55 years old. Both girl's and boy's optimal age is significantly earlier than is suggested by current models.
5) Endurance training for both boys and girls should begin from 9 years of age.
