My son grew four inches between March and September when he was thirteen. Four inches. His shoes went up two sizes, his forehand went into the next zip code, and his ranking fell off a cliff.
For about six months, he played like he’d never held a racquet. Shots he’d hit in his sleep at twelve were suddenly flying. His feet were always in the wrong place. He’d get angry, I’d get worried, and his coach just smiled and said: “He’s growing. This is normal.”
He was right. But nobody had warned us it would look like that.
The coordination dip is real (and temporary)
Here’s what’s happening inside a growing junior: bones grow first, fast. Muscles, tendons, and the brain’s map of the body catch up later. For a few months, your kid is operating levers that are longer than the ones their brain calibrated. The result is the teenage version of a puppy tripping over its own paws.
Youth development coaches have a name for it — adolescent awkwardness — and it’s one of the most well-documented phases in junior athletics. Timing goes. Balance wobbles. A kid who moved beautifully at twelve looks clumsy at thirteen and a half.
How long does it last? Typically a few months per growth spurt, sometimes up to a year for the big ones. It is not a technique problem. It is not a coaching problem. It is not your kid “losing it.” It’s physics and biology, and the only way through is through.
The single most important thing a parent can do during this phase: don’t panic about rankings. The kids who look great at thirteen are often the ones who grew early and finished. Your late bloomer isn’t behind — they’re mid-construction.
New power, new demands
Here’s the flip side: post-puberty, your kid is suddenly strong. The serve has real pop. The forehand has weight it never had. This feels like a breakthrough, and it is — but it comes with a technical bill.
Power without control is just errors. A thirteen-year-old who could get away with a flat, muscled forehand at twelve will start spraying balls when the new strength arrives. The swing that worked for a smaller body doesn’t automatically work for a bigger, stronger one.
This is the moment spin becomes more important, not less. Remember the topspin equation: more racquet speed + spin = controlled power. The kids who already hit with shape can pour on the new strength and keep the ball in. The kids who hit flat just hit their misses harder. Growth spurts are where the flat-hitter’s cliff starts — the technique debt comes due exactly when the body changes.
Footwork changes too. Longer legs mean a different stride pattern, different spacing to the ball, different recovery steps. Juniors in growth spurts need footwork drilling more than ever — not less. The feet have to learn the new body before the hands can trust it.
The awkward phase: what’s normal
Normal during a growth spurt:
- Timing that’s inexplicably off for weeks or months
- Balls flying long (new levers, same old swing calibration)
- Tripping, stumbling, looking uncoordinated doing things that used to be automatic
- Frustration and confidence dips — this is genuinely hard on kids
- A temporary ranking slide
Not normal — talk to someone:
- Sharp, persistent joint pain (not muscle soreness — joint pain)
- Pain that doesn’t fade with rest days
- Limping or visibly favoring one side
- One leg or arm suddenly much weaker than the other
Injury watch for growing bodies
Growing athletes get injured differently than adults, and parents should know the greatest-hits list:
Growth plate injuries. The ends of growing bones have cartilage growth plates — they’re softer and more vulnerable than adult bone. A fall or overload that would bruise an adult can injure a growth plate in a thirteen-year-old. Any significant joint injury in a growing kid deserves a doctor’s look, not a “walk it off.”
Osgood-Schlatter. The classic: a painful bump just below the kneecap in kids roughly 10–15. It’s the tendon pulling on the growth plate where it attaches to the shin. Extremely common in running and jumping sports — tennis included. Usually manageable with rest, ice, and activity modification, but get it diagnosed rather than guessing.
Sever’s disease. The heel version — pain at the back of the heel in kids roughly 8–15, where the Achilles pulls on the heel’s growth plate. Same story: common, usually manageable, worth a proper diagnosis.
The overuse trap. Here’s the one parents control: a kid who just grew four inches and suddenly serves 15 mph faster is putting new forces through new levers. This is not the time to add tournaments. Growth spurts are when smart coaches actually dial volume back slightly and focus on movement quality. More is not better when the body is rebuilding itself.
The rule that covers almost everything: soreness fades, pain persists. Muscle soreness after a hard week is normal. Joint pain that shows up every session, pain that changes how they move, or any sharp pain — that’s a sports medicine visit. Don’t negotiate with it.
What parents can actually do
Be patient out loud. Your kid knows they look terrible. They don’t need you confirming it. “Your body’s changing, the timing will come back” said calmly, repeatedly, matters more than any drill.
Protect the love of the game. Growth-spurt slumps end more tennis careers than injuries do — kids decide they’re “just not good anymore” and quit. Keep it fun. Play goofy games. Remind them (and yourself) that the thirteen-year-old ranking doesn’t determine anything.
Talk to the coach. A good junior coach has seen fifty growth spurts. Ask: “Are we adjusting anything while he’s growing?” The right answers involve footwork, patience, maybe slightly reduced volume. The wrong answer is “he just needs to toughen up.”
Don’t compare. The early developer dominating at thirteen and your kid struggling at thirteen are on different timelines, not different trajectories. Some of the best pros were late growers. The body arrives when it arrives.
The bottom line
Post-puberty tennis is a rebuild disguised as a slump. The body changes, the timing goes, the power arrives before the control does — and then, usually within a year, it all comes back better than before. The kids who survive this phase with their confidence and love of the game intact are the ones whose parents understood what was happening.
Your kid isn’t broken. They’re under construction.
We’re parents, not doctors or coaches — this is general information from our experience and research, not medical advice. If your kid has persistent pain, see a pediatrician or sports medicine doctor. When in doubt, get it checked.
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