This Month in Journals: Does Birthdate Matter in Winning, or Staying In, Youth Sports?

Chelsea LittleAugust 15, 20147
Born in November 1993, Lennart Metz of Germany was one of the oldest competitors at Junior World Championships in 2013. Did that help him win the classic sprint? Photo: Liberec2013.
Born in November 1993, Lennart Metz of Germany was one of the oldest competitors at Junior World Championships in 2013. Did that help him win the classic sprint? Photo: Liberec2013.

From children’s racing through Masters World Championships, athletes are divided into age classes in order to ensure fair competition and to identify the best racers at different developmental stages. In fact, only at the senior elite level is birthday a non-factor in determining what race you can win.

But how are these age groups defined? A group of researchers in Switzerland asked whether being born earlier or later in the year impacted athletic success and opportunity.

The concept is called “relative age effect” (RAE) and describes how within a given a give age class, for example J2 ski racers in the United States, birthdates might have a skewed distribution. For instance, being born earlier in the year might confer an advantage because young athletes might have developed further or simply grown taller.

At junior national championships, a skier who is 15 years and 11 months old, for instance, might be significantly stronger and have more developed ski technique than one who is 14 years and 3 months old. He or she might also be more mentally mature and have a better handle on high-pressure competition situations.

Looking at age distributions at championship events, you can see hints of this pattern. Look at 2013 World Junior Championships in skiing, for example. In the men’s classic sprint, half of the final heat comprised athletes born in the last five months of 1993, at the edge of the age eligibility window. It might have been because they were bigger, stronger, or faster – or that they’d had better development opportunities because as very young skiers, they were identified as talent earlier.

(In other sports, there is a “reverse RAE” where being younger is advantageous.)

Michael Romann and Jörg Fuchslocher applied these questions specifically to young female athletes in primarily individual sports. Both are areas lacking substantial research: across all sports science, male athletes are much better-represented as study subjects, and furthermore there is plenty of money and resources to investigate high-profile team sports with robust development structures, such as soccer.

Those previous studies found that young male soccer players were more likely to drop out of sport if they had late birthdays making them relatively younger than the rest of their age class, for instance. But with significant physiological differences between men and women, differences in the ages at which male and female athletes hit puberty and mature, and even in technique and ideal body type for men and women in some sports, the same wouldn’t necessarily be true for girls.

For instance, look back at that World Junior Championships in 2013: in the women’s sprint final, the second- and fourth-place finishers, Victoria Carl of Germany and Natalia Nepryaeva of Germany, were born in 1995 – they weren’t even the oldest classes of juniors at that point.

Romann and Fuchslocher used data from 301,428 young women (age 10-20) participating in Switzerland’s recreational “Youth and Sport” programs, and looked at a subset of 1,177 young women involved in the National Talent Development Program in several sports to look for RAE’s.

Among the greater dataset of women in the recreational program, athletes had earlier birthdays than would be predicted by the overall Swiss distribution in alpine skiing, tennis, track and field, snowboarding, and fencing.

Results were different among the most dedicated young athletes, though. In the National Talent Development program, where athletes train at least 400 hours per year, there were more early birthday for alpine skiing and tennis, but more late birthdays for snowboarding, table tennis, and fencing.

The authors noted that this represented considerably more variation in the strength and direction of relative age effects at the elite youth level than has previously been found for male athletes. One reason, the authors suggested, might be that societal pressure contributes in different ways to girls’ decisions to participate or stay in sports.

For instance, media and culture push the idea that being feminine means having a specific body type – a thin and delicate one. That is at odds with the idea body type for many sports, where size and muscle are advantageous. They argue that girls who mature earlier might be more cognizant of these pressures, drop out of sports where physicality is important, and switch, for example, from tennis to table tennis, which is more technical and where having a traditionally “feminine” body type might be less of a disadvantage.

Likewise, the combination of RAE’s and reverse RAE’s might be because girls initially enroll in the most high-profile sports (in Switzerland, alpine skiing and tennis), but the younger, less physically strong participants might drop out when they realize they don’t have as good a chance of success. If they then switch to sports like snowboarding and fencing, this could explain why there are a higher prevalence of late birthdays in these second-tier sports.

At the recreational level, though, it seems clear that girls at the younger end of the yearly age distributions are less likely to enroll or stay involved in sports. This presents two problems. One is elite- and woman-specific. In countries like Switzerland where women’s national teams are often quite small compared to the full rosters of men’s teams (for example, the country didn’t send a female biathlete to the Olympics until 2010), as many young female athletes as possible should be encouraged to continue in sports.

But at a more general level, for both girls and the previously-studied young male athletes, dropping out of sports represents an obstacle for those pushing the health and social benefits of lifelong recreational sports. If having a late birthday means that you are less active and less likely to develop sports-based social bonds with friends, there are potential public health consequences.

Several unwieldy solutions have been suggested, such as making competitive or weight classes rather than age classes, as is done in judo; making age classes narrower, for instance with 6-month spans to minimize the age differences between competitors; or changing what time of year the cutoff dates fall at each season so that athletes will always have a relative age advantage at least once in their career.

Instead, the authors suggest, perhaps a solution can begin with the attitudes of youth sports coaches. If youth teams prioritize long-term development and potential rather than immediate performance, they might be more likely to select or invest in a smaller, younger athlete who nevertheless might excel in a few years’ time. After all, schemes like Switzerland’s National Talent Development Program by definition should be thinking long-term.

The concept and consequences of relative age effects should be taught in coaching education programs, they added.

Chelsea Little

Chelsea Little is FasterSkier's Editor-At-Large. A former racer at Ford Sayre, Dartmouth College and the Craftsbury Green Racing Project, she is a PhD candidate in aquatic ecology in the @Altermatt_lab at Eawag, the Swiss Federal Institute of Aquatic Science and Technology in Zurich, Switzerland. You can follow her on twitter @ChelskiLittle.

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  • highstream

    August 16, 2014 at 11:47 am

    What a complex matter! Are the age groupings appropriate? Are coaches smart enough and sensitive enough to handle developmental issues? How much can they do given limited resources? How do adolescent physical maturation and peer, cultural and parental influences affect youth decision making? Etc., etc.

    Ross Tucker of The Science of Sports website discusses this issue generally in a British Medical Joural podcast at (question starts at 3:45 – follows discussion of the 10,000 hour myth. Also discussions of how much one needs to drink during exercise, exercise (and spectatoring) in heat, barefoot vs. shoed running.

  • Tim Kelley

    August 16, 2014 at 10:09 pm

    Highstream: When Northug won his first World Cup at 18, did it make a difference that his birthday was in January or December? Likely not (he was born in January and was just over 18 years old when he won his first WC). Birthdates might have a minor statistically significance for average competitors. But when it comes to greatness, it’s not complex … genetics trump what month you were born every time.

  • highstream

    August 17, 2014 at 11:45 am

    Tim, you seem to have missed the main point of Chelsea’s article. And if you listen to Tucker’s podcast, he speaks to the very issue you raise, how the birthdate difference disappears around 18-19. That doesn’t help those younger than that. In fact, it’s a sufficient issue that the international Little League has voted to change their age rules to Dec 31 as the marking date, instead of summer, effective 2018. While there still will be differences, it won’t be 13 year olds pitching to just-turned 12’s.

  • dougherty.andrew

    August 17, 2014 at 8:49 pm

    Interesting article on RAE, but this summary seems misleading. In skiing, athletes born at the beginning of the year are the oldest in their age groups. The caption suggesting that Metz was older because he was born in November would be the reverse RAE effect according to the study.

  • davord

    August 18, 2014 at 12:39 am

    Tim, it did make a difference, because Northug was actually 20 when he won his first world cup…You are also putting too much stock into genetics.

  • Chelsea Little

    August 18, 2014 at 5:01 am

    Good catch, Andrew – I really botched that one! There is little research on RAE’s in cross-country skiing; one study in males reportedly found “normal” RAE’s, which would probably be expected. For girls it has never been considered. Cross country skiers were not included in this Swiss study, I’m guessing because of small sample size: there are less than 100 women with FIS licenses in Switzerland in total, 47 of whom are under the age of 20. If that’s indicative of the number in the National Development Program, then that wouldn’t probably be enough to consider whether RAE’s are at work or if so in what direction.

  • skidog

    August 19, 2014 at 1:26 pm

    “…might drop out when they realize they don’t have as good a chance of success”
    I agree that it is a complex matter, but I can’t help feeling like success is the biggest factor: being successful is a huge motivator to carry on and work on developing your skills. My son has really taken to BMX racing and I’ve been very impressed with the programming. Kids race in the age group that coresponds with their age on the day of the race. On their birthday, they move up, regardless of the time of year. Any individual sport can use this system. Furthermore, proficiency classes are layered on top of age classes, so you have, for example, 3 six year old classes: 6 novice, 6 intermediate, and 6 expert. Kids who have won 10 races (ever) become intermediates. After 20 wins you become an expert. With this much breakdown, there is sometimes a problem filling classes, but each club is provided with software that optimizes the entries on race day so that classes are combined to ensure everyone gets to race: somtimes you might race older or more experience kids, other days you might race younger, less experienced kids, so it all evens out. This system affords a great deal of opportunity for kids to be successful as they age and as their winning peers are graduated out of their pool. I’ve really enjoyed watching it work.

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