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.

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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.

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This study reports

Participant (1)

195 boys aged 15~18 yrsLongitudinal data

Attended the school 1982～2003

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Participant (2)

5

22 boys aged 15~17 yrs

test-takers of the 2007 2nd-exams

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Measurements Height & Weight

(students, test-takers) TW3 skeletal maturity

(test-takers)

Predict Adult Height by AUXAL3

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Adult Heightat 25 yrs

data for 6 to 15 yrs(test-takers)

BTT

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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

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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

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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

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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

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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.

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