Growth Spurts and Slower Swim Times: a Parent's Guide

The Saturday that doesn't add up

I grew up racing in Ireland, and I still remember the quiet in the car when a teammate who had been dropping all winter suddenly looked lost in a 100 free. Same work. Same coach. New legs. The balcony only had one sentence: they had gone backwards.

Parents get this job because the number is so clean. When it is slower than the one on the fridge, every other explanation feels like an excuse. It is not. Rapid height gain changes the machine: entry a few centimetres late, a catch that slips, a turn that feels behind. This is not a diagnosis or a reason to pile on extra kilometres. It is a pattern coaches have watched for decades — the body stretches, the stroke has to be relearned, the clock can stall.

What growth actually does in the water

Sports science talks about peak height velocity (PHV): the months when a child is growing up fastest. Before that window, average height gain is often around six centimetres a year. Through the spurt it can rise towards nine in girls and ten in boys — research averages, not a promise for your child. Legs often lengthen before the trunk. Muscle and tendon catch up later, so the segments get longer and heavier before the swimmer has the strength and the feel to move them the old way.

That mismatch is nicknamed adolescent awkwardness. Coordination can wobble during the steep stretch and, for some, for months afterwards. The stroke that used to be automatic — entry, kick, wall, breakout — is suddenly a slightly different job. Height and arm span still help speed in the long run. The awkward bit is the transition: new levers, old timing.

That is why “just swim more” is a poor balcony prescription. Extra kilometres on a child who is already growing hard and sleeping badly are rarely the missing piece. Sleep, food, and patience are. Technique that fits the new body — the coach’s call — beats a set of race-pace 50s invented in the gallery.

Typical ages — girls often earlier than boys

PHV is a range, not a birthday. Reviews of youth athletes often put the steepest stretch around 11.5 to 12 in girls and around 13.5 to 14 in boys, with a couple of years either side still ordinary. That is why the same 13–14 heat can hold a child who finished growing last year and a child who has barely started.

Those are population averages, not a test you run at home. Early-maturing boys can look like a different sport for a year, which is why talent talk gets noisy at 13. Late-maturing girls may keep a more linear shape for longer. None of that is a verdict on who will be fast at 18 — only a reason not to crown or write off a child from one winter of adds.

This is not the same as mid-season times looking worse

We already wrote the training-load version: why mid-season times look worse. Read that if Saturday was a tired gala in a heavy block and the whole squad looked flat. This page is the other story — the one child whose body is rewriting the stroke. Both can be true in the same month. Tell them apart instead of stacking every add into one panic.

Patterns, not diagnoses. A child can sit in both columns. Pain, a sudden drop with injury signs, or a lasting collapse in mood or sleep is never “just growth.”

Irish age groups, 31 December, and the 13-year-old question

The search that lands families here is often “why is my 13-year-old adding time.” Thirteen is a crowded year: many girls have already been through the steepest stretch, many boys are heading into it, and some have just aged up.

Swim Ireland usually sets competition age as age on 31 December of the year of the meet. A January 2013 birthday and a December 2013 birthday can both race as “13” in 2026 — almost a year of extra growing between them. Schools meets may use 31 August; some club galas still use age on the day. The heat sheet prints the band, not biological age.

Aging up into 13–14 can look like going backwards even when their own time has barely moved. Placings fall because the field got older. Watch their times, not month-one rank. Relative age — January versus December — is real in Irish and UK age-group swimming, and it usually matters less by the late teens.

An illustrative dip — then the clock comes back

There is no official PHV time-loss chart for Irish club swimming. Families describe a shape: honest work, a messy patch, then a return once the new proportions stop fighting the stroke. Treat the graph as a sketch, not data.

What it looks like at home

The clock is one column. The house is the other. Parents often notice the growth story first — the coach sees a lane; you see the shoes.

• ✓Kit and trainers jumping a size — sleeves short, the old racing suit suddenly modest.
• ✓Sleep they still need: often nine hours, and they are getting seven.
• ✓Hunger that looks theatrical until you remember they are building a new skeleton.
• ✓A stroke that feels late or slippy — the water feels different, not that they did not try.
• ✓Adds that survive an easier week, unlike a whole-squad mid-season slump.
• ✓No sharp pain. Tired and awkward is one thing; a shoulder, knee, heel, or back that hurts is another.

What parents can actually do

You cannot timetable puberty. You can stop the car-park inquest from becoming the main set of the weekend.

Lead with the child. “How did that feel?” beats “you were two seconds slower” before the kit bag is in the boot. They already know the clock. They need to know they are not in trouble for growing.

Keep one list — same event, same course, including the ugly galas. How to organise that is how to track swimming times. Do not mix 25-metre and 50-metre clocks into one “best 100.”

Write how they felt — tired, clumsy, strong, hungry, sore. Protect sleep and food the way you would a taper week. Let the coach handle technique on the new body. Yours is the lift home, and not turning one heat into a referendum on whether they still have it.

When to talk to the coach — or a GP

Most growth-related adds belong here: awkward, hungry, still turning up. The right-hand list is not “they missed a PB.” It is a reason to stop guessing.

If you are in the right column, talk to the coach with facts — last few meets, the course, what you see at home. If pain is in the picture, a GP or physio is not overreacting. Take pain seriously, and do not diagnose it from a website. This page is not medical advice. Finzy does not diagnose or treat injury. We keep the numbers and the notes so a qualified human can see the winter in one place.

Log the time and the feel

I built Finzy so a family can keep race times without a spreadsheet argument. The clock tells you what happened. The note — tired, clumsy, grand — tells you why Saturday felt like a different sport. Together they stop one heat from becoming a 13-year-old’s whole personality. When the stroke catches the new limbs, you will want the ugly months still on the page.

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