Date of Birth and Development Birthdate, Relative Age and “Whoever wishes to investigate medicine Athlete Development properly, should proceed thus: in the first place to consider the seasons of the year, and what effects each of them produces Joe Baker for they are not at all alike, but differ much from themselves in regard to their Lifespan Health & Performance Laboratory York University, Toronto, Canada changes.” Hippocrates (400BC) Lifespan Health and Performance Laboratory Season of birth effects relate to seasonal Date of Birth and Development environments experienced during gestation which have the potential to Hippocrates (400BC) significantly influence healthy development. Season of Birth Research SOB related to: Thought to be driven by biological Schizophrenia/Bipolar Disorder processes. Anorexia Nervosa/Bulimia Obesity Myopia Longevity Lifespan Health and Performance Laboratory Lifespan Health and Performance Laboratory 1
Date of Birth and Development Relative age effects relate to differences perceived to exist among individuals due Relative Age refers to age compared to others in the same to differences in their age compared to cohort or age group. peers. September 2006 October 2006 November 2006 December 2006 Thought to be driven by socially-constructed processes. January 2007 February 2007 March 2007 April 2007 May 2007 June 2007 July 2007 August 2007 Lifespan Health and Performance Laboratory Relative Age Effects Relative Age Effects In education In education • Attainment scores (Bell et al., 1997; Cobley et al., in press) 5.5 • Gifted and talented (Cobley et al., in press; Sharp, 1995; 5.25 Thompson, 1971) 5 • Learning disabilities ( Bookbinder, 1967; Cobley et al., in Pupil Attainment 4.75 Physical Education press; Wilson, 2000) Mathematics 4.5 Science 4.25 Quartile 1 = Sep - Nov Quartile 2 = Dec - Feb 4 Quartile 3 = Mar - May 3.75 Quartile 4 = Jun - Aug 3.5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 School Year 7 School Year 8 School Year 9 Relative Age (Birth-Date Quartiles) Lifespan Health and Performance Laboratory (Cobley et al., in press) 2
Relative Age Effects Relative Age Effects In sports In sports NHL Draftees 400 (Canadian and American Data) 350 300 250 200 150 100 50 0 Jan-Mar Apr-Jun Jul-Sep Oct-Dec Baker & Logan (2007) BJSM Relative Age Effects Relative Age Effects In sports In sports Australian Data NBL 40% MLB Rugby League 300 35% (American Data) Rugby Union 250 30% AFL 200 25% 150 20% 100 15% 50 10% 5% 0 Jan-Mar Apr-Jun Jul-Sep Oct-Dec 0% 1 2 3 4 Cote, MacDonald, Baker & Abernethy (2006) JSS Abernethy & Farrow (2005) ISSP 3
Relative Age Effects Relative Age Effects In sports In sports Germany (Handball data) NBA (American Data) Q1 Q2 140 50 Q3 Q4 40 120 30 100 20 80 10 60 0 40 D-squad D/C-squad C-squad B-squad A-squad 20 0 Jan-Mar Apr-Jun Jul-Sep Oct-Dec Schorer, Cobley, Büsch, Bräutigam, & Baker (in prep.) Cote, MacDonald, Baker & Abernethy (2006) JSS Relative Age Effects Relative Age Effects In sports In sports PGA Women’s Hockey 35.0% 60 (American Data) (Canadian data) 30.0% 50 25.0% 40 20.0% 30 15.0% 20 10.0% 10 5.0% 0 0.0% Jan-Mar Apr-Jun Jul-Sep Oct-Dec Jan - Mar Apr - Jun Jul - Sep Oct - Dec Cote, MacDonald, Baker & Abernethy (2006) JSS Wattie, Baker, Cobley & Montelpare (2007) IJSP 4
Where do relative age effects come Relative Age Effects from? In sports • Historical examinations • Elite athlete status • Gifted and talented (Cobley, Abraham & Baker, in press) • Representative sport (Baker et al., under review) Lifespan Health and Performance Laboratory Lifespan Health and Performance Laboratory RAE History: Canadian NHL Players RAE History: German Soccer Players 140 ** ** ** 120 Jan - Mar 200 Apr - June Quartile 1 100 175 July - Sept Quartile 2 Oct - Dec 150 Quartile 3 80 Quartile 4 ** 125 60 100 ** 40 75 20 50 25 0 <1900 1901-1905 1906-1910 1911-1915 1916-1920 1921-1925 1926-1930 1931-1935 1936-1940 1941-1945 1946-1950 1951-1955 1956-1960 1961-1965 1966-1970 1971-1975 1976-1980 0 1935 and 1936- 1941- 1946- 1951- 1956- 1961- 1966- 1971- 1976- 1981 and below 1940 1945 1950 1955 1960 1965 1970 1975 1980 above* Wattie, Baker, Cobley & Montelpare (2007) IJSP Cobley, Schorer & Baker (2007) Under Review 5
Where do relative age effects come Where do relative age effects come from? from? •Historical examinations •Historical examinations •Causal hypotheses •Causal hypotheses 1) Maturational Factors 1) Maturational Factors – Baker et al., under review 2) Psychological Factors – Positive appraisal from parents & coaches (Pygmalion Effect) – Relatively younger players dropout early (Barnsley & Thompson, 1988) Lifespan Health and Performance Laboratory Lifespan Health and Performance Laboratory Where do relative age effects come Relative Age Implications from? •Historical examinations • Achievement and attainment in education and sport •Causal hypotheses • Overall physical activity participation – Dropout (Barnsley & Thompson 1988; Helsen et al., 1998) 1) Maturational Factors • Impact on self-perceptions, self-appraisals and motivation 2) Psychological Factors – Self-esteem (Barnsley et al., 2004) 3) Experiential Factors – School Attendance (Carroll, 1992; Cobley et al., in press) – Cf. Vaeyens et al. (2005) and Baker et al. (under • Adolescent mortality review) – Youth Suicide (Thompson, Barnsley & Dyck, 1999) Lifespan Health and Performance Laboratory 6
Is it always an advantage to be relatively older? Wattie et al. Pediatrics, 2007 • Relative age and injury 45.0% 40.0% 35.0% 30.0% 25.0% Q1 Q4 20.0% 15.0% 10.0% 5.0% 0.0% House Intermediate A AA AAA Is it always an advantage to be Solutions? relatively older? • Re-adjustment of age ranges • Relative age and injury • Teacher/Coach Education • Relative age and draft order – Cobley et al (2007) – Relatively younger athletes were more sought after in the NHL draft (Baker & Logan, 2007) Attainment 1 2 3 4 7
Solutions? On-going Research – Relative age and PA/obesity? • Re-adjustment of age ranges – Relative age in talent identification? • Teacher/Coach Education – Relative age and psychological development? – Moderators of the relative age effect? – Cobley et al (2007) – Causes/Solutions? Attainment 1 2 3 4 8
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