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Growth and Maturity of Japanese Jockey Candidates
1
Shozo TAKAI Institute of Health and Sport
Sciences, University of Tsukuba, Japan takai@taiiku.tsukuba.ac.jp http://biking.taiiku.tsukuba.ac.jp/ XI International Congress of
Auxology, Tokyo, Sept. 9--12, 2007
Background
Jockeys are regulated to low weight about 50kg.
Jockey candidates need to 44.0kg to 46.5kg to admit the Horse Racing School, Japan Racing Association.
Jockey candidates need to 47.5kg to pass out the School.
2
Jockeys must keep their weight at low level.
Purpose
height and weight growth for students while in the Horse Racing School for 3 years.
skeletal maturity and predicted adult height for test-takers of the 2nd-stage exams of the school.
3
This study reports
Participant (1)
195 boys aged 15~18 yrsLongitudinal data
Attended the school 1982~2003
4
Participant (2)
5
22 boys aged 15~17 yrs
test-takers of the 2007 2nd-exams
6
Measurements Height & Weight
(students, test-takers) TW3 skeletal maturity
(test-takers)
Predict Adult Height by AUXAL3
7
Adult Heightat 25 yrs
data for 6 to 15 yrs(test-takers)
BTT
8
Height Growth for Students97
90
75
50
2510
3
10
011
01
20
13
01
40
15
01
60
17
01
80
19
0
6 7 8 9 10 11 12 13 14 15 16 17 18
cm
Age (years)
Height
Jpn_OgiBoys
JJ
JJ
Median values fell between 3rd and 10th centiles of the Japanese reference.
9
Weight Growth for Students97
90
75
50
25
10
3
10
20
30
40
50
60
70
80
6 7 8 9 10 11 12 13 14 15 16 17 18
kg
Age (years)
Weight
Jpn_OgiBoys
JJ
JJ
Median values fell below 3rd centile of the Japanese reference.
Correlation of Weight to Height for Students
10
r=0.42 r=0.37
r=0.39 r=0.30
(15.5 yrs) (16.5 yrs)
(17.5 yrs) (18.3 yrs)
Correlation was the lowest at graduation
Skeletal Maturity for Test-takers
11
3
10
2550
7590
97100
200
300
400
500
600
700
800
900
1000
6 7 8 9 10 11 12 13 14 15 16 17 18
Sco
re
Age (years)
RUS (TW3)Maturity Score
Jpn _OgiBoys
JJ
J
J
JJ
J
J
J
J
J
J
JJ
J
JJ
J
JJ
JJ Values fell below median of the Japanese reference.
Height for Test-takers
12
Values fell below 25th centile of the Japanese reference.
10
011
01
20
13
01
40
15
01
60
17
01
80
19
0
6 7 8 9 10 11 12 13 14 15 16 17 18
cm
Age (years)
JJ
J
J
J
JJ
J
J
J
J
JJJJJ
J
J
JJ
J
J
97
90
75
50
2510
3
Height
Jpn_OgiBoys
13
Weight for Test-takers
Values fell below 10th centile of the Japanese reference.
97
90
75
50
25
10
10
20
30
40
50
60
70
80
6 7 8 9 10 11 12 13 14 15 16 17 18
kg
Age (years)
3
JJJ
J
J
J J
J
JJ
JJ
J
J
JJJ
J
JJJJ
Weight
Jpn_OgiBoys
Predicted Adult Heightfor Test-takers
14
count
count
TW3
count
Jpn TW2 (Takai)Growth potential(Sato et al.)
count
BTTTW3 and BTT estimated taller adult height.
Conclusion
Small and immature boys took an exam. Growing status of the students was low
while in the school. The small was attributed to restricted
daily calorie intake (2,100 kcal) and exercising.
The selectivity and exclusivity of horse racing is related to the results.
15
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