For my kids to be good at sport, should we plan to give birth within the 1st 3 months of the year?


In a recent review published in Sports Medicine, leaders in the area Nick Wattie, Jorg Schorer and Joe Baker discuss how birth date cannot determine sport participation and success. At least on it’s own that is.

The relationship between birth date (usually based on month) relative to peers in an age-grouping year and the attainment of sporting success is known as the Relative Age Effect. The typical explanation for this phenomenon is that children who are relatively older within an age-grouping year are physically more mature. This physical maturity is then mistaken for ability.

Wattie, Schorer and Baker argue however, that sport participation and sporting success is not that simple, but rather a product of the interaction of a number of factors – birth date being just one.

To help us understand this complex issue, our colleagues apply what is known as the constraints-based model. The model basically describes and categorises factors (or constraints) that govern our actions. These categories are individual constraints (for example, height, weight, birth date, etc), task constraints (for example, demands of the sport, goals, performance context, etc) and environmental constraints (for example, policies, family, coach influence etc). These constraints can both restrict or facilitate. Think about driving a car to get from point A to point B. The car represents the individual constraints; we can only go as fast as the car allows us to go. The task constraints represent the driver of the car; his goal is to get from point A to B. And environment = the road, its rules and other obstacles.

The key point though is that all these constraints need to interact with each other to produce its effects. In our driving analogy, we won’t get to our destination if the car, driver or roads are not functional. Therefore, birth date (an individual constraint) itself is meaningless in terms of predicting sporting success. Birth date gives rise to the effects of relative age however, when it interacts with an age-grouping policy for sport (an environmental constraint). Add to this the physical demands of the sport (a task constraint), and boom, children born in the earlier part of the year seem to emerge as having an advantage.


If anything changes during our trip from A to B, the tyres on the car, or the road is bumpier than anticipated, it will affect the other constraints (for example the driver) along the way. Likewise, if we change anything at the individual, task or environmental level, it will affect the other constraints. Lets not also forget that things will change over the journey, and every journey from point A to B is different – this speaks to the plasticity and diversity of the Wattie, Schorer and Baker model.

Although theoretical for now, the proposed model invites us to think differently about the Relative Age Effect phenomenon. This has implications for the way we collect, analyse and interpret the relationship between birth date and sporting success. And of course, no need to plan giving birth within the 1st 3 months of the year for your kids to be good at sport.

For the full article, go to –

Wattie, N., Schorer, J., & Baker, J. (2015). The relative age effect in sport: A developmental systems model. Sports Medicine45(1), 83-94.

Sharief Hendricks

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