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  • Writer's pictureGary Moller

When is it Appropriate for Your Child to Focus on One Sport? A Guide for Parents

So: when should a child specialise in sport?

"It's Allometry Dear Watson"

(Sherlock Holmes)


Lorraine and Dad, running through Pinedale Forest

I started athletic training at around 16 years old, following my younger sister, Lorraine. I ran with her as she developed as a runner and went on to have an incredible 28-year career as an internationally ranked athlete. For some 55 years now, I've rubbed shoulders with many great athletes, including Olympians, world champions, and world record holders. I've learned what it takes to be the best.

The harsh truth is that only a minuscule percentage of those promising child athletes training hard several times a week will ever be great and enduring athletes. The reality is that winning the national lottery might be a better bet than a child making their fame and fortune on the sports field.

I'm not meaning to be a killjoy, but a realist and to caution parents not to put all of their child's eggs in the "sporting" basket.

I'm now in my 70's and still as competitive in sport as I was in my 20's and I'm loving every minute of it. Done right — planned well — sport is for life. I'm proud to add that my four children, all now adults, are continuing their love of being physically fit and strong, and still enjoying the cut and thrust of sporting competition.

The best strategy, one that worked very well for me, the much less talented child of the Moller siblings, was and is to do the following:

  • Expose your child to many different sporting activities, and outdoor pursuits.

  • Develop an intrinsic enjoyment of the mere act of being physically fit and active.

  • Develop a love and joy of being in the Great Outdoors.

  • Focus attention on the process, such as the satisfaction of hitting the ball in the "sweet spot", rather than the outcome.

  • Make sure there's plenty of healthy, enjoyable socialisation, within and outside of sport.

  • Even for those at the top, realise sport is still just a game and not to be taken too seriously.

  • Losing isn't the end of the world!

  • Emphasise the golden rule in sport: "Humble in victory while gracious in defeat".

  • For the vast majority, few athletes will ever be able to make a living from their sport, and for those who manage, this may be only for a few years.

  • Make sure the child athlete doesn't sacrifice their academic education and the attainment of marketable skills such as a trade.

Summary for busy people:

  1. This article discusses the concept of "allometric scaling" and how it relates to child athletes and their potential for success.

  2. Allometric scaling states that if an organism doubles in size, its power increases by only about 2/3rds.

  3. This principle is why children have a greater power-to-weight ratio than adults, making them better suited for sports requiring quick acceleration and changes in direction.

  4. As a result, children can achieve impressive athletic feats, but it doesn't guarantee future success.

  5. Most precocious child athletes (90 percent or more) never reach their full potential and fade into obscurity after puberty.

  6. Early specialisation in a single sport before reaching physical maturity can be detrimental, as the power-to-weight ratio naturally decreases with age.

  7. Instead, children should engage in a variety of sports and activities to develop all-around physical and mental skills.

  8. Overspecialisation and early success can lead to frustration and disappointment when athletes face natural declines in performance due to physical changes.

  9. Parents and coaches should prioritise the child's well-being, education, and enjoyment over short-term athletic success.

  10. Coaches should create a safe, supportive environment, focusing on long-term development while avoiding injury or burnout.

  11. Child athletes should have a backup career plan as the chances of earning substantial wealth through sports are slim, and many athletes face financial struggles after retirement.

  12. Allometric scaling is a scientific principle that describes how organisms' characteristics change with size and has implications for understanding the physical capabilities of children versus adults.


With the exception of a small number of sports, such as gymnastics, it's strongly advised that parents and coaches don't encourage children, including teenagers, to specialise before they've reached physical maturity. This caution is based on the scientific concept of "allometric scaling," which lies at the core of this issue. I'm disappointed that the principles of allometric scaling aren't widely understood and are seldom taught to exercise scientists and coaches. Even when it's taught, it's often disregarded in pursuit of immediate success and the praise and recognition that comes with it.

What is Allometric Scaling?

The science of allometric scaling dictates that if an organism doubles in size, power increases only by a factor of about 2/3rds.

This is why an ant can jump many times its height, whereas an elephant can't jump at all. The larger the organism, the less its power to weight ratio. This is why an ant would collapse under its own weight if it were scaled to elephant size and why the elephant must have very thick, short legs and can't jump. The same maths applies to accelerating and decelerating a body: The more the object's mass, disproportionally more energy is required to accelerate and decelerate it.

Examples to illustrate the point:

The clean-and-jerk world record for the featherweight (under 61 KG) weight category is 175 KG, whereas, for the super-heavyweight (+109 KG) it's 263 KG.

The super-heavyweight weighed in at 168 kilograms at the time of setting this world record, whereas the featherweight was less than 61 kilograms.

Ratio: Featherweight​=5.21 kg/kg

Ratio: Super Heavyweight​=2.88 kg/kg

So, the percent difference between Featherweight and Super-Heavyweight ratios is an astonishing 57.6 percent.

So a 61 KG weight lifter can lift more per kg body weight that a 168 KG one. In addition, the athlete having the smaller mass, and thus the greater power-to-weight ratio, can quickly accelerate quicker than a larger opponent, and to quickly change direction. This is why a small rugby player tends to be able to out-manoeuvre a larger opponent.

Size is an advantage in sports that don't require lifting and lowering body weight. Therefore, a big rower or kayaker will have an advantage over a smaller opponent. The same applies to cycling — a big rider will have an advantage on a flat course, or in a velodrome, whereas the lighter rider will have it over a larger, heavier rider on the hills. When running, a small runner has the advantage over a larger one in any event longer than about 200m. This is because each stride raises and lowers the body weight by several centimetres. Power-to-weight ratio outweighs total power. This is principally why extremely slightly-built runners dominate world distance running.

Let's do some more mathematics:

The importance of power-to-weight ratio in sport

Calculating power-to-weight ratios is easy, and here's an example for cycling:

For calculating power-to-weight ratios, we can use the formula:

Power-to-weight ratio=Body weight (in kg). Oxygen uptake (in mL)​

Since oxygen uptake is typically measured in litres per minute, and the power-to-weight ratio is in millilitres of oxygen per kilogramme per minute, we need to convert litres to millilitres by multiplying by 1,000.

For the 65-kg cyclist with a maximum oxygen uptake of four litres per minute:

Power-to-weight ratio=65 kg4 L×1000 mL/L​

Power-to-weight ratio=65 kg4000 mL​

Power-to-weight ratio=61.54 ml O2​/kg

For the 85-kg cyclist with a maximum oxygen uptake of five litres:

Power-to-weight ratio=85 kg5 L×1000 mL/L​

Power-to-weight ratio=85 kg5000 mL​

Power-to-weight ratio=58.82 ml O2​/kg

So, the power-to-weight ratio for the 65 kg cyclist is about 61.54 ML O2/kg/minute, and for the 85 kg cyclist, it's about 58.82 ML O2/kg/minute.

The difference in percentage between the power-to-weight ratios for the two cyclists is 4.52 percent. This is significant in a sport where the winner may be determined by a difference of less than a second.

On flat terrain, the 85 KG cyclist has a 4.5 percent advantage over the 65 kg cyclist due to sheer horsepower. However, on hilly courses or those requiring constant acceleration, deceleration, and changes of direction, the 65 KG cyclist should have the edge. The steeper and larger the hills, the better it is for the lighter cyclist. This advantage holds true except on long descents, where the heavier cyclist's momentum can be an advantage.

We see these principles in action in races like the Tour de France. Riders under 60 KG dominate the mountain passes, while heavier riders tend to dominate the flat sections, including the time trials. If the lighter riders haven't burned them out on the hills, the heavier riders often win the sprint finishes.

In sports like swimming and rowing, where there's minimal raising and lowering of bodyweight, sheer horsepower dominates. To compensate, some sports like rowing, have lightweight divisions.

A sport like female gymnastics, favours the light pre-pubescant physique, and it's rare to see a physically matured female gymnast able to compete at the higher levels of the sport.

Winning comes too easy for the Precocious Child Athlete

Thanks to our knowledge of allometric scaling, we can now understand why children who undergo intense training can achieve incredible levels of physical performance. These are activities such as running, mountain biking, and gymnastics, which require a strong power-to-weight ratio to excel.

It's not uncommon to hear about the child athlete who breaks age-group records and is then announced to the world that they are compared to super athletes such as Peter Snell, destined for sporting greatness. However, history tells us that 90 percent or more of these precocious athletes are destined never to reach their full potential. Instead, they'll fade into obscurity after puberty.

Let's face it, physical maturity isn't fully achieved until around the age of 28 years. Although total power will naturally increase as an athlete matures, the power-to-weight ratio will decrease unless deliberate measures are taken to mitigate this decline. We'll explore these measures in more detail shortly. In a sport like running, or cycling, other than on flat ground, their performance may fail to improve all that much and may even go backwards.

While winning may come easy for the child athlete who undertakes "adult" training, they may never learn how to handle losing. As a child athlete matures, despite rigorous training, they'll naturally encounter an allometric decline in their power-to-weight ratio. This decline can lead to frustration and doubt, as the athlete may struggle to maintain their previous level of performance. All they've known until then, during influential developmental years is the dopamine shot that comes from winning, and the acclaim of peers, parents — everyone — thus tying their identity with being the glorious "forever winner"!

As a young athlete growing up during the 1970's, our wise parents and coaches insisted on this:

Be it a game of rugby, or a running race, the winners and losers were always expected to shake their opponent's hand afterwards and congratulate each other with positive words and a smile.

"Always humble in victory, while gracious in defeat".

Words of caution:

When a precocious child athlete starts losing instead of winning, as is inevitable, it threatens their singular definition of self. This can lead the athlete to resort to extreme measures, such as cheating, using performance-enhancing drugs, taking puberty blockers, developing anorexia or bulimia, or, in the case of a male athlete, even declaring themselves transgender. After all, if winning with ease is the goal, and the only thing that matters in life, why not take any means necessary to achieve it, including changing one's sexual identity!

You are your Mother and your Father:

As a young person goes through puberty, body changes can be dramatic and one can't defy physical laws such as those to do with allometric scaling. One can get an idea of what that skinny little kid might grow into by looking at his or her parents and close relatives. A child who demonstrates talent shouldn't over-specialise in one particular discipline, or role within a team until they are well on the way to physical maturity — about 18–24 years. This gives them the option to switch to the event and role that their body and interests best suit and also to find out what they really enjoy doing. Of course, there are always exceptions to the rules of physics, but these people are rare.

Are parents vicariously projecting their unfulfilled dreams of glory through their child?

Are parents who were disappointed with their own relentless quest for fulfilment by athletic glory, unwittingly projecting their lost dreams onto and through their unsuspecting and innocent children? Are they thereby burdening their child with the weight of their unrealised aspirations?

There are arguments to be made for encouraging children of athlete parents to participate in sports other than those their parents excelled in, particularly for the sake of their mental health. I've observed numerous instances over the years where the children of gifted athletes have instinctively resisted following in their parents' footsteps, instead choosing completely different pursuits, not necessarily related to sports.

Sporting Glory - The unattainable Holy Grail for most child athletes

The sad fact is, ninety-nine percent of those thousands of children around the country engaging in athletic training most days of the week will have given up by the time they're 18 years old. For girls, it's more like 14 or 15 years. For those that continue with serious training, it's still inevitable that fewer than five percent of those remaining will ever win an olympic or world championships medal. Nor will they be able to make a living, and if they do, this will be only for a few short years.

Be wary of the ambitious coach!

There are only two kinds of coaches:

Those that have been fired and those that are about to be fired.

A coach is judged by just one thing: winning this season! If they don't produce winners right away, they're fired, or ambitious parents take their precocious children elsewhere. If the athlete is in a high-performance programme, the additional pressure this places upon them and their coach to produce winning performances this year and not in ten years can be extreme.

So, here's the problem: The child athlete is typically pushed and thrashed several times a week, while having fun, socialisation and their academic achievement takes a back seat. Taking a developmental approach with the child is either not understood or it's ignored. Short-term gains and glory are favoured over nurturing the physical and psychological skills needed for a productive, happy, and satifying life. When there's true physical and emotional maturity in their mid-to late 20's, then is the time to begin the Olympic-level of training and intense competition!

Though shalt not injure, or burnout!

When coaching young and talented athletes, it's important to remember

"First, do no harm!"

Coaches must create a safe and nurturing environment that puts the athlete's physical and mental well-being first. Young athletes often face a lot of pressure to perform beyond their age. This can lead to physical injuries and mental exhaustion.

Coaches need to balance the athlete's athletic development with their overall well-being. This means making sure they get enough rest and recovery and avoiding training or competition that could put their future performance at risk. For example, a knee injury during their teenage years could have long-term consequences, forever limiting their peak potential performance. The coach should adopt a strategy that focuses on long-term growth and development, while also considering the physical and mental capacity of the young athlete at their current stage of maturation.

Coaches should also create a supportive, fun-filled atmosphere that values personal growth, including socialisation and academic achievement as much as athletic success. The young athlete needs to understand the love of the process and not the adulation of winning is most important. Winning, while it's still important, is the bonus that comes from loving and enjoying the process.

By following these principles, coaches can help their athletes reach their full potential without the risk of injury or burnout.

Where's the career backup plan for athletes?

Throughout my life, I've been surrounded by great athletes, including world and Olympic champions from many sports. I've seen many examples of truly remarkable athletes who, upon reaching the end of their sporting careers, discovered they had no backup plan. While this was especially a crisis during the amateur years, when even a world champion retired as a pauper, the problem still exists today.

The reality of sporting life, even in today's professional era, is that only a tiny fraction of those precocious young athletes will ever earn enough money to retire comfortably in their 30s. In fact, they're more likely to retire broke and without a trade or qualification to fall back on. If they've managed to save some money, they're often pressured to invest it in risky schemes, risking losing everything due to their business and financial naivety.

Linking achievement in sports with a child's sense of value is a risky notion, as it results in them solely focusing on athletic success and neglecting the opportunity to prepare for an alternative career path.

Parents and coaches, take note: It's crucial that precocious athletes don't sacrifice their education for the sake of chasing often unattainable sporting glory. They need to have a practical career to turn to when the inevitable time for retirement comes around.

End of article


For Nerds who want to know more about allometric scaling

Allometric scaling is a scientific concept that describes how the characteristics of living organisms change with size. It's based on the observation that the biological form and function of organisms don't scale proportionally with body size. This phenomenon can be seen in various biological aspects, such as metabolic rates, lifespan, growth rates, and the size of body parts.

The science behind allometric scaling often involves the relationship between the size of a body part and the size of the body, especially as they grow during development. For example, the size of an animal's heart doesn't increase linearly with its body size; instead, it follows a specific scaling law. These scaling laws are typically characterised by a power-law relationship of the form:

Y = Y_0 M^bY=Y0​Mb

Here, ( Y) is the biological variable of interest. (M) is the body mass. (b) is the scaling exponent, and (Y_0) is a constant. The exponent (b) is often a simple multiple of one-quarter or three-quarters, rather than one-third, which would be expected if the relationships were purely linear. The idea in the science of allometric scaling is fractal network theory, which I've still yet to get my head around.

This theory says that allometric scaling laws, like the 3/4 power law for metabolic rates, happen because essential materials move through branching tube networks, like blood vessels, that fill space like a fractal. This theory says that these networks are set up to move things around in the best way possible. They use the least amount of energy to deliver nutrients and take away waste products. Allometric scaling is important in biology, ecology, and evolution.

It explains how organisms of different sizes work and interact with their environment. Understanding these scaling relationships is crucial for predicting the behaviour of biological systems and for applying this knowledge in fields like conservation, medicine, and environmental management.

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