Using training age to gauge athlete experience

Training age provides an indirect measure of an athlete's experience in sport

A few weeks ago I wrote about how retention and training age are important metrics that national sport governing bodies (NGBs) can use to gauge the strength of their athlete population. In this edition of the newsletter I want to dive a little deeper into training age because I think it's one of those things that sounds obvious but turns out to be a bit more complicated once you start thinking about it. (If you do your own taxes then you know the feeling.)

We deal with several different 'ages' of the athletes we work with. Chronological age is calculated from an athlete's date of birth to the current day. It's useful in sport because when combined with sex it becomes our primary method of categorizing athletes -- maybe not the best way but certainly the easiest.

Though easy it's not the most accurate way because it does not adjust for maturational differences. For example, two 13-year-olds might be wildly different in height, weight, strength, and speed due simply to different rates of growth. We know these differences will narrow or even disappear with age but while they exist using chronological age to group these athletes together is not very useful. For a number of months or even years the bigger athlete will almost always outperform the smaller one.

The point is that while chronological age is the most common way to group athletes it does have limitations. Calculating maturity offsets can identify differences in maturity levels and help mitigate limitations.

We also use relative age, which is not really an age at all but a general assessment used to gauge maturational differences between athletes of the same chronological age. I'll be writing about relative age in a few weeks.

Training age (TA) is not widely used and may have different meanings depending on who is using it as well as different ways of calculating it. At the high performance level TA usually represents how much of a specific kind of training an athlete has done (speed, resistance, etc.) and for how long.

At the developmental level tracking the specific type of training isn't important nor is it practical. Sportkid Metrics treats TA as a general measure of how long individual athletes have been involved in sports. It's not widely used because although it's easy to calculate -- it's just counting really -- the data to count from is not readily available. NGBs could easily calculate this metric if they wanted to from their membership databases. This doesn't happen for some reason though. (I’ve never seen training age reported by NGBs. If you have please let me know.)

Average training age is an aggregate metric of athlete TAs overall or athlete TAs separated into various categories such as sex or chronological age.

How is training age measured?

TA is measured simply by counting the number of years that an athlete has been involved in a sport. The clock starts running when a child is first registered (TA=0) and continues with each subsequent year of participation.

TA is a proxy for experience so all sport participation is counted. Youngsters sampling sports are counted in the same way as those specializing, since it doesn't make any difference if experience is gained in one sport or several. Note that current youth sport recommendations support sampling at young ages rather than specializing in one. In the lingo this is known as the generalization to specialization pathway. The benefits of sampling over specialization will be covered in a future letter.

How is it used?

TA and average TA can be used by coaches at game or training level, or by NGBs for management of the athlete population.

Average TAs represent the overall performance strength of the NGB. Rising average TAs are good news. At a more granular level average TAs can be calculated for age groups (Table 1). When used in conjunction with retention numbers, average TA can be a powerful analysis tool for administrators.

At the competition level, experience can often be a strategic factor. Knowing the experience level of their athletes coaches can make informed decisions about tactics, replacements, relay exchanges, etc. In some cases the average TA of the athletes on the floor is important; in other situations the actual TA of individuals is more relevant. For example, in relay exchanges actual TA has more influence on the result than the average would. TA is probably not the critical factor but it gives coaches another tool to work with.

Tracking training age: What it looks like

In developmental sport we're always dealing with age groups of some kind, so it makes sense to analyze the interaction between TA and chronological age. Doing this illustrates the effectiveness of retention efforts. Average TAs that rise with chronological age indicate good retention of athletes. Stagnant or declining average TAs indicate a loss of experience from the sport and retention metrics heading in the wrong direction.

Table 1 shows what tracking average TA across single-year age groups looks like. As expected, the average TA is low in the younger ages and rises as athletes get older. Many of you may be surprised that while average TA does rise as athletes age, it doesn't ever reach very high values. In Table 1, for example, the average TA for 18-year-olds is just slightly over three years. To understand these numbers let's run through how they are calculated:

  • Averages: These numbers are averages, so each chronological age group consists of athletes who have been registered for x years as well as new athletes (TA=0).
  • TAs increase naturally with age: Many athletes in younger ages are new (TA=0) or have been involved for a single year (TA=1). Only a small number of 7-, 8-, or 9-year-olds have TAs over 1 year. As a result, the youngest age groups have the lowest average TAs. Likewise, older age groups consist mostly of athletes who have been involved in sport for more than a year or two. Because of the way TA increases in individuals, lower ages always have lower average TAs compared to older ages, so overall average TA is not a very informative metric. In Table 1, for example, the overall average TA is 2.11 years but the range spans 0.24 to 3.06.
  • Dropout and replacement: A certain number of athletes dropout of the sport as they age. At younger ages the ones that dropout are replaced by new athletes (TA=0). At older ages TA increases slightly because fewer new athletes are joining. While new athletes join at all ages the largest number of these are in younger age groups.
  • Overall attrition: According to the National Alliance for Youth Sports 70% of children quit playing sports by age 13*, thus skewing the TA upward in older age groups.* As is shown in Figure 1, TAs for the 10- to 12-year-olds have a shallow but steady increase until about 12 years where there is a steep jump upward, which may account for some dropout without new (TA=0) replacements.


When is TA no longer useful?

Tracking training age vs. chronological age (Table 1) is useful up to a certain point, but eventually the TA metric loses its value. At some point it no longer makes sense to calculate it.

Recall that the importance of measuring retention is to see if NGBs are engaging athletes long enough for them to develop their own reasons for investment in the sport. Training age has a similar use. Up to a certain TA the experience gained by youngsters adds to their ability and performance. These improvements are closely tied to their experience level, their TA. After a certain age -- and no one has established a definitive number for this -- improvements due to experience alone diminish rapidly and substantially. Improvements are no longer the result of simply showing up but rather the components we typically associate with athletic training.

Simply showing up at young ages is often all it takes to develop skills enough to shine in youth sports. As we all know though this improvement from simply being there doesn't last but if youngsters can garner enough experience to where they enjoy the game, develop a bit of self-efficacy about their participation, and experience a little bit of success along the way then they are far more likely to stick with it long enough to make a difference. Training age is how this individual engagement is measured. And if you haven't heard me say this before I'll say it again: Time is the most important factor in developing sport ability.


Training age is another metric that sport practitioners can use to measure progress. It can help coaches understand what a young athlete may be bringing to the table in terms of experience, knowledge about training, and the sport overall. It’s valuable to NGBs as they attempt to understand and manage the developmental level of their sport.

  • Note: Even though you have probably seen this statistic in a number of places I have not been able to track down where it originated. Unfortunately, I have to say that the more I hear it without any substantive reference I think it is either just made up or it is just being repeated again and again because it's one of those things that just sounds like it could be right. The National Alliance for Youth Sports has not responded to my email regarding this matter.