The Bit Nobody Warns You About: What the Summer Holidays Actually Do to Your Child's Body — and Why It Sometimes Ends Their Sport
The summer holidays are about to start, and most British parents are currently thinking about logistics. Childcare gaps. Holiday clubs. Days with grandparents. The two weeks abroad. The bit that almost nobody is thinking about, because nobody has told them to, is what the six weeks ahead will quietly do to their child's body — and what some of that quiet change means for their child's relationship with sport, fitness, and movement well into adolescence.
I want to write about it now, in mid-June, because the choices that matter for how a child's September goes are mostly choices made between now and the end of August. The good news is that the things that help are mostly straightforward. The point of this piece is to make sure you know what they are before the holidays start, not after.
Every September, children walk into our dojos in Knaphill and Merrow Village showing a pattern that I and most experienced coaches recognise immediately: a temporary loss of coordination, a subtle drop in balance, a body that doesn't quite move the way the child's parents tell me it usually does. It's most visible in children — particularly in the eight-to-thirteen bracket — who haven't done much structured physical activity across the summer.
The September pattern is not random, it isn't bad luck, and it isn't just about getting out of practice. It's a window of genuine biological vulnerability that the research has only properly understood in the last fifteen years, and that has implications well beyond the start of the school year. A proportion of the children who quietly fall out of love with sport between the ages of nine and fourteen do so because of something that happened in this window — something that nobody around them recognised as a window at the time it was happening.
This isn't a piece designed to make any parent feel guilty about giving their child a proper break. Children need rest. Families need holidays. Nobody's child needs a summer training schedule. It's a piece designed to give the parent who cares about their child's long-term relationship with movement the information their GP probably hasn't given them, and that most school PE teachers don't have time to explain. If that's you, this is for you.
What the Research Has Been Showing
There's a body of academic research, going back about fifteen years, on a phenomenon sports scientists call adolescent awkwardness. It's been studied most intensely in football academies, but the underlying mechanism applies across youth sport.
The basic finding is this: during periods of rapid growth, children can temporarily lose coordination. Their motor skills regress. Their balance gets worse. Their spatial awareness — the unconscious sense of where their body is in space — fragments. They become more prone to tripping, dropping things, mistiming movements, and getting injured. The most thorough academic review of the field, published in 2025, summarises the consensus: rapid growth and coordination loss are linked, though the researchers themselves note that the field is still working out the precise relationship.
I want to be honest about one thing the same review flags, because the research isn't quite as tidy as it's sometimes made to sound. There is no single accepted definition of adolescent awkwardness. There's no standardised test for it. Some researchers question whether the coordination loss is genuinely universal or whether it's a phenomenon that affects some children much more than others. The strongest finding is that some children, during some growth phases, show measurable coordination regression and elevated injury risk. The strongest finding is not that every child going through a growth phase becomes uncoordinated. So I'll try not to overclaim.
But the underlying mechanism, where it does occur, is well understood. When a child grows, the bones lengthen first. The muscles, tendons and the nervous system that controls them all have to catch up. There is a window — sometimes a few weeks, sometimes a few months — where the child is, in a literal mechanical sense, working a new body with a brain that still has the old body's internal map. They reach for a glass and their hand goes slightly past it. They go to step up onto a kerb and their foot clips the edge. They try a movement that they used to do without thinking and the timing is off because their arms are now slightly longer than their brain thinks they are.
Researchers call this internal recalibration the body schema update. Children call it being clumsy. Parents call it that strange phase where their kid suddenly seems to be tripping over everything.
The vast majority of academic writing on this focuses on full adolescence — the proper growth spurt around ages eleven to fourteen, where peak height velocity hits and the effects are most dramatic. But the same underlying mechanism, in milder form, can play out every time a younger child grows quickly over a short period. Including, in many cases, over a six-week summer holiday.
Why the Summer Specifically
Children don't grow at a steady rate. They grow in bursts — sometimes overnight, sometimes over a few weeks, sometimes in concentrated runs over a season. And the long summer holiday turns out to be one of those concentrated runs for a lot of children.
There are a few reasons why. They sleep more during the holidays. They eat more, because they're not in school routine and meals get bigger. They spend more time outdoors and get more sunlight, which affects growth hormone release. And — significantly — they typically do less hard physical activity than during term time, which means the muscular and tendon adaptations that usually keep pace with bone growth fall behind.
The activity data on this is genuinely sobering. A UK study using accelerometers — actual movement sensors, not parental self-report — found that children's moderate-to-vigorous activity drops by around 45% over the summer holidays compared to term time, and doesn't fully recover until the following spring. Another UK study found children spent 70 extra minutes a day on screens during the summer break and lost 12 minutes a day of moderate-to-vigorous activity.
I should add — because the research deserves it — that not every study agrees on the same scale of effect. Some studies find smaller activity drops, particularly in families that prioritise outdoor holiday activity. And some studies find that more affluent families show less of a summer activity decline than less affluent families, which suggests the summer-loss phenomenon is partly about access to facilities and structured activity rather than about something universal in children. The point is not that every British child loses 45% of their activity over six weeks. The point is that a great many do, and that the children who do are the ones we tend to see arrive at the dojo in September showing the pattern this piece is about.
So picture what's happening to many children between mid-July and early September. They grow — a centimetre, maybe two, maybe more. Their bones lengthen. Their muscles, tendons and motor control don't keep pace because the daily movement that drives those adaptations has dropped sharply. By the time they walk through the school gates — or the dojo doors — in September, they are, biomechanically, a slightly different child than the one who finished the summer term. Taller. Less conditioned. With a nervous system that hasn't had recent practice updating its internal map of where their limbs now are.
And Here's the Bit Nobody Tells You
This is where the story takes a turn that I think every parent needs to hear, because it's the bit that determines what your child's relationship with sport looks like in five, ten, twenty years.
Researchers have known for some time that previous injury is one of the strongest predictors of premature drop-out from sport. Children who get injured don't always come back. The ones who do come back are at a meaningfully higher risk of getting injured again, which then makes another drop-out more likely.
Layer that onto the September scenario and you can see the shape of the problem. A child who comes back to sport after a summer growth burst may be at higher risk of injury exactly when they're most likely to feel demoralised by their temporary loss of coordination. If they pick up an injury — even a small one, like a strain or a rolled ankle — they may be off for two to four weeks. They come back to find their team-mates or training partners further ahead. They feel behind. They feel clumsy. The brain quietly starts to make the connection: sport hurts. Sport makes me feel bad. Sport isn't for me.
A small but meaningful proportion of children who quit sport between the ages of nine and fourteen are, on the data, quitting because of an injury that happened in a window of growth-related vulnerability that nobody around them — parents, coaches, teachers — recognised as a vulnerability.
This is the piece I find most uncomfortable to write, because it means that the September moment isn't just about a child being a bit slower than they were in July. It's about an unrecognised risk window in which the wrong injury, at the wrong time, can shape a child's relationship with their own physicality for life.
The good news — and there is good news — is that the research has now identified what to do about it. And it's not what most parents would assume.
What the Research Says Actually Works
A major piece of research published in 2023 looked at male academy footballers going through the adolescent growth spurt — the moment of maximum awkwardness and injury risk. The researchers identified which players were in the risk window and put them through a specific intervention: modified training load, targeted balance work, coordination drills, and an individualised strength programme.
The result was extraordinary. For the highest-risk players, injury incidence dropped by 86% and injury burden dropped by 92% compared to the previous season.
I'll add the necessary caveat: this was a study of elite male academy footballers, not ordinary recreational children. It's reasonable to assume the same direction of effect at the community level — the underlying biomechanics don't change because a child is at a smaller club — but it would be wrong to assume the size of the effect translates directly. The honest claim from the research is that targeted balance, coordination and strength work during growth phases substantially reduces injury risk in young athletes. The size of the protection varies with the population and the intervention. We can be confident the direction is right; we shouldn't pretend the exact numbers transfer to every child.
But the principle is what matters, and the principle is clear. A child going through a growth phase is not destined to get hurt. They are not destined to lose confidence. They are not destined to fall out of love with sport. They are, however, in a window where the kind of activity they're doing matters enormously. The wrong kind of activity — high-load, high-impact, repetitive, with no attention paid to coordination and balance — is what produces the injuries that drive drop-out. The right kind of activity — varied, balance-focused, coordination-rich, allowing the body to rebuild its map of itself in safe conditions — is what protects them.
And here is the piece I want every parent reading this to take seriously:
The summer holidays are, for many children, the worst possible moment to take them out of structured movement — because they are the moment a child most needs it.
The instinct most parents have — that the summer is a break, and the child will be fine going back to their sport in September — is, biomechanically, often backwards. The summer is when their body is changing most. It's when their nervous system most needs the steady drip of varied movement that keeps the internal map updated. It's when a six-week pause in regular structured activity does the most cumulative damage, because every week away can be a week of bone growth without the matching muscular and neural adaptation that would have happened in term time.
What You Can Actually Do About It
I want to be practical here. I'm not telling any parent that their child needs to train through the entire summer. Children need rest. Families need holidays. Routines need to break. None of that is in dispute.
What I am saying is that the worst-case version of the summer — six weeks of no structured physical activity, lots of screen time, lots of growth, no rebuilding of the coordination map — is what produces the September problem. And there are plenty of ways to avoid that without ruining the holiday.
One. Don't pull your child entirely out of their sport for the full holidays.
Even one session a week through August is meaningfully different from six weeks of nothing. The child's nervous system stays in conversation with the activity. The coordination doesn't deteriorate to the same degree. When September comes, they're not coming back to a new body from cold — they're picking up where they left off.
Two. Watch for the visible signs of a growth phase.
Trousers suddenly too short. Shoes that fitted in June pinching by August. A child who seems to be tripping or dropping things more than usual. Increased complaints of leg or knee aches at the end of the day. Any of these are signs your child is in a growth window, and during such a window, more varied movement helps and less hurts.
Three. Prefer varied, coordination-rich activities over repetitive, high-impact ones during growth phases.
Swimming is excellent during a growth phase because it's full-body, varied, and low-impact. Climbing is excellent because it requires constant proprioceptive feedback — the body is always telling the brain where it is. Judo, in case I haven't been obvious about why I'm writing this, is excellent because the entire activity is built around controlled falling, balance, and learning to use a new body in space. Repetitive high-impact activities — long-distance running, intensive jumping sports, heavy weight training — are the activities to be most careful about during growth phases.
Four. If your child does get a small injury, don't let them disappear from the sport.
This is the one most parents get wrong, and I say it gently. A child who picks up an ankle sprain or a strain and is then off the sport for a month often doesn't come back. The momentum is broken, the team-mates have moved on, the confidence wobbles. Even if they can't train at full intensity, get them back in the room. Let them watch. Let them help out. Let them do the warm-up. The relationship to the sport — and to the people in it — matters more than the lost training time.
Five. Take the September return seriously.
The first two or three weeks back are when injuries are most likely. They're also when confidence is most fragile. The right approach in that window is patience, varied work, lots of balance and coordination drills, and reduced expectations about technical performance. The wrong approach is to push hard to "catch up" — which is when the injuries happen and the disengagement starts.
The Longer View
I want to close by widening the lens, because the September moment isn't really the point of this piece. The point is what the September moment can do to a child's whole life.
A child who has a bad September — who comes back clumsy, gets hurt, loses confidence, and disengages — is, on the research, meaningfully less likely to be physically active as an adolescent. A physically inactive adolescent is, on the research, much less likely to be a physically active adult. And a physically inactive adult is, on the research, statistically at the start of a long line that includes worse mental health, worse physical health, worse social connection, and a shorter life.
That sounds dramatic. But the data is clear: the body habits a child has at fourteen are, for most people, the body habits they have at forty. And those habits get set, partly, in moments like September — moments where a child's relationship with their own body is fragile, where the right kind of support keeps them in the room, and where the wrong kind of pause sends them out of it.
The summer holidays are not the cause of this. Lots of factors are. But the summer holidays are one of the moments in a child's year where parents have unusually high leverage — and where the decisions about what to do, or not do, with their child's body have unusually long-term consequences.
We run weekly Tigers, SuperKids, Juniors and Teens classes at our clubs in Knaphill, Woking and Merrow Village, Guildford throughout the summer holidays, with only a two-week closure in August.
If you'd like to keep your child moving through the summer — or if you've been thinking about getting them into judo and the September moment in this piece has made you pause — we offer a FREE 14-day VIP pass. Three or four sessions, no commitment, no pressure. Long enough to know whether judo is something they'd love.
— Vince