Nakata Hiroki
Department of Health Sciences, Faculty of Human Life and Environment, Nara Women's University, Kitauoya-Nishi Machi, Nara city, 630-8506, Japan.
Sports Med Open. 2017 Dec;3(1):21. doi: 10.1186/s40798-017-0090-3. Epub 2017 Jun 2.
The mechanisms underlying the relative age effect in sport events have been investigated for more than two decades. The present study focused on the relationship between the relative age effect and lengths of professional careers among professional male Japanese baseball players.
The birth dates of players and lengths of professional careers were collected from an official publication, and data were divided into four quarters (Q1: April-June; Q2: July-September; Q3: October-December; Q4: January-March of the following year) grouped by 3 years. Based on the data for Q4, the expected numbers for the lengths of professional careers were calculated for Q1, Q2, and Q3.
The number of players with professional careers of more than 19 years was significantly smaller in Q4 than in Q1, Q2, and Q3.
The relative age effect among professional male Japanese baseball players was associated with the lengths of professional careers. Relative age appears to be a very important factor for the development of expertise among male Japanese baseball players and involves long-term disadvantages after becoming professional players.
二十多年来，人们一直在研究体育赛事中相对年龄效应的潜在机制。本研究聚焦于日本职业男性棒球运动员的相对年龄效应与职业生涯长度之间的关系。
从一份官方出版物中收集球员的出生日期和职业生涯长度数据，并按3年分组划分为四个季度（第一季度：4月至6月；第二季度：7月至9月；第三季度：10月至12月；第四季度：次年1月至3月）。根据第四季度的数据，计算第一季度、第二季度和第三季度职业生涯长度的预期人数。
职业生涯超过19年的球员数量在第四季度显著少于第一季度、第二季度和第三季度。
日本职业男性棒球运动员中的相对年龄效应与职业生涯长度相关。相对年龄似乎是日本男性棒球运动员专业技能发展的一个非常重要的因素，并且在成为职业球员后会带来长期的不利影响。
