It's probably the first question that crosses your mind when you hear about CrossFit for children. A gym, barbells, weights, and your eight-year-old in the middle of it all. The concern is fair and deserves a calm answer, because the idea that strength training stunts growth has been around for decades and has never had any science behind it.
This article does three things. It explains where the myth came from, shows what paediatric and sports medicine organisations say today, and describes what your child actually does in a class at Revolution, by age group. By the end you'll have what you need to decide, not a sales pitch.
If you're not quite sure what the programme is yet, start with the benefits of CrossFit Kids. Here we go straight to the safety question.
Where the idea that strength training stunts growth came from
The fear centres on one specific part of the bone: the growth plate, the cartilage at the ends of the long bones that closes at the end of adolescence. The reasoning seems logical. If the area is cartilage, and cartilage is more fragile than bone, then putting load on it must be a bad idea.
What fuelled the belief were old reports of injuries in that area in young people. When you look at those cases closely, the same pattern almost always appears: maximal loads, no supervision, technique nobody corrected, often at home or in a gym with no coaching. It wasn't strength training that was the problem. It was strength training done in the worst possible way, which you wouldn't do to an adult either.
From there, the myth went the usual way: it was repeated so many times that it started to sound like common sense.
What paediatric and sports medicine organisations say today
The current position is clear and comes from three independent sources.
The American College of Sports Medicine puts it plainly: there is no scientific evidence that taking part in a well-designed strength training programme slows children's growth or harms the developing skeleton. More than that, it notes that strength activity at this stage of life can increase bone mineral content and density, in other words, the documented effect goes in the opposite direction to the fear.
In 2020 the American Academy of Pediatrics published the clinical report Resistance Training for Children and Adolescents, which revises its 2008 position and was reaffirmed in November 2024. It considers strength training safe for children and adolescents as long as there is proper supervision and correct technique, and recommends starting with low resistance until the movement is well learned, only then adding load in small increments.
And there is a 2014 international consensus, published in the British Journal of Sports Medicine (Lloyd, Faigenbaum and colleagues, 48(7):498-505), adapted from the UK Strength and Conditioning Association position statement and reviewed and endorsed by sports medicine, exercise science and paediatric organisations.
Notice what these three sources have in common. None of them says “weights are safe for children, full stop”. They all make the answer depend on the same thing: qualified supervision, the right dose and technique before load. That's the real question you should be asking a gym.
The right question isn't “weights or no weights”, it's “who's coaching”
A child alone at home trying to copy a video with a dumbbell is at risk. The same child in a structured class, with a coach who knows what stage of development they're at, corrects their posture and decides when to add load, faces a risk comparable to any organised sport, and lower than many.
It's also worth saying what's rarely said: the alternative to coached training isn't “no risk”. It's a child who spends the afternoon sitting down, who never learned to fall, jump or stop, and who reaches fourteen with poor movement patterns. That has a cost too, it just doesn't show up as an injury on a particular date.
What your child actually does in a class, by age
This is the part that clears up most doubts, because many people picture a miniature version of adult training. It isn't that. At Revolution there are three separate programmes, from 5 to 16 years old, and the content changes completely between them. The sessions don't use heavy Olympic barbells.
Kids, 5 to 8 years old
There are no weights here. The work is the child's own body and a PVC pipe, which weighs practically nothing and is used to learn hand position and the path of the movement. Running, forward rolls, jumps, press-ups and games. The goal is for them to learn to move well and to enjoy the hour they spend here.
This fits exactly with the American Academy of Pediatrics guidance that at 5 years old strength is built with jumping and bodyweight work, not with external load.
Preteens, 9 to 12 years old
This is the bridge between playing and training properly. Lifts come in, but the word that matters is the one that follows: with technique. Gymnastics and teamwork are added. Intensity goes up, load is still a detail and not the focus of the class.
Teens, 13 to 16 years old
Structured training, with strength and conditioning, cardiovascular work and close coaching. At this age the body already responds to training much like a young adult's, and what sets them apart is the care taken with progression and volume, not a lack of challenge.
How many times a week, and how it fits around school
Two sessions during the week plus the Saturday one is the pattern for most kids who train at Revolution, and it's enough. Weekday classes are in the late afternoon, after school.
| Group | Ages | Weekdays | Saturday |
|---|---|---|---|
| CF Kids and CF Pre-Teens | 5 to 12 years old | Monday and Wednesday, 17h20 | 11h15 |
| CF Teens | 13 to 16 years old | Tuesday and Thursday, 17h45 | 11h50 |
The full timetable, with the adult classes at the same time, is on the timetable page. And yes, that's on purpose: while your child trains, you can train too.
The signs that it is going well, and the signs that it is not
You don't need to know about training to judge. Three things tell you almost everything.
He wants to go back. A child who enjoys what they do turns up the following week without being dragged. If you have to negotiate every single session, something isn't working, and it's worth talking to the coach before giving up.
Talk about what they learned, not who won. At this age what matters is the new movement, the forward roll that finally worked, the jump that now reaches the box. If what comes home is always comparison with others, the environment isn't the right one.
They sleep and eat normally. Healthy tiredness goes away after a night's sleep. Pain that lasts for days, or a complaint that keeps coming back in the same spot, is something to tell the coach and, if it persists, the paediatrician.
Questions parents ask
My child isn't sporty at all. Can they do it?
Yes, and it's often those who start from a low base who see the biggest difference. As every class has several options for the same exercise, kids with different starting points train together without it being obvious.
What if they already play football?
It works well alongside it, and it's one of the most common uses. One session a week working on what their sport doesn't, coordination, mobility and general strength, is usually more useful than more training of the same thing. Talk to the coach to match the volume to their training sessions and matches.
Will they lift weights alongside adults?
No. The younger ones' classes are in their own group, with their own timetable and a dedicated coach.
How much does it cost?
The plan for under-16s is 50 € a month with direct debit. When you join there's the registration fee and the annual insurance, one-off amounts that aren't repeated. You'll find everything under prices, with no hidden fees and no contract.
The first class is free, and that's how you decide
Nothing written here replaces seeing it. Bring your child to a class, stay and watch, look at their face at the end and talk to the coach. The first class is free and commits you to nothing.
You can book on the CrossFit Kids page or talk directly to the team on contacts. If you're comparing places in the area, the CrossFit Kids in Figueira da Foz page has the practical info on where we are and how to get here.
One last note, said honestly: we will not promise you that your child will get taller, stronger or more focused by training here. What the evidence supports is more modest and more useful than that. Supervised strength training does not stunt growth, and a child who learns early to enjoy moving takes that habit into adult life. The rest is the Saturday class at 11h15.
If the question you're left with is how much exercise a child needs in total, we explain the 60 minutes a day the WHO recommends, and what counts towards it.
