I don’t train as many junior players now as I have in the past. It’s not that I don’t want to, it’s just that I’m in a position right now where older players - those that are playing professionally (either on a full-time or part-time basis) - take up a big chunk of my time.
That said, I still manage to coach a number of younger players (both in-person and remote). The ages range but generally fall between 9 and 15… and all of them are exposed to strength training in one form or another.
The reason I’m bringing this up is because I often get asked by parents… “is lifting weights dangerous?” or “will lifting weights stunt my child’s growth?”...
This post won’t be a long one as many in the fitness space have already written about this (think Cressey, Boyle and others) but I’ll impart some of my own evidence on the whole “is lifting weights bad for kids?” topic.
Before we get into the details, I want to first say that it’s completely normal for a parent to ask this question. I mean, most parents (unless they’ve been educated on the topic), probably should ask the question…so I’m not trying to belittle anyone here, I just want to bring up a few points that will hopefully add some clarity.
1 - The Scientific Evidence
Here’s an excerpt from Faigenbaum et al 2015 on the decline of physical literacy in today’s youth (note, Faigenbaum has been the lead researcher on youth strength training for decades)...
“Ten year secular trends in muscular fitness in English children indicate declines in bent arm hang, sit up performance and handgrip strength….similar trends were observed in selected measures of motor fitness (eg, shuttle run and plate tapping) in Dutch primary school children and muscular power (eg, long jump and vertical jump) in Spanish adolescents. Australian researchers reported low levels of motor skill competence in school-age youth, and noted a clear and consistent association between low competency in motor skills and inadequate levels of cardiorespiratory fitness.”
While youth that are involved in sport have a clear edge when it comes to physical literacy, beyond sport play, many aren’t being developed in other areas. For example, I coach a 15 year old that has gym class once every 9 school days!!! While he trains 5-6 days a week (tennis and/or fitness), it’s still a shocking realization… today’s youth just aren’t as active as they once were. Side note - at his age, I had physical education daily in high school...and I would go to the gym, play organized + unorganized sport on my own time (and most of my friends were in similar positions)...and this was just 20 years ago.
Faigenbaum on the benefits of strength training to performance and injury prevention...
“Regardless of sporting success, young athletes who do not address neuromuscular deficits early in life are less likely to sustain high-level performance and more likely to suffer a ‘preventable’ sports injury. For example, weakness in the hamstrings, supraspinatus and middle trapezius were associated with an increased risk of injury in, retrospectively, young female athletes, adolescent baseball pitchers and age-group swimmers.
The authors add...
“A certain level of force-production and force-attenuation is required to perform all athletic movements, and therefore the importance of enhancing muscular fitness should be considered foundational to athletic development.”
According to the literature, it appears that strength training has an impact on all other physical qualities (but more on that below).
2 - Practical Evidence
I’ve noted many training observations with youth over the years. While I am now working with older players, there was a time I coached primarily juniors…
First, you need to understand that we use a conjugate type system in our training programs (i.e. all - or most - qualities are trained all the time; with greater emphasis given to some instead of others...depending on time of year, athlete needs and so on). For instance, we might do more traditional acceleration/speed work early on in the training year and less of it once tournaments are on the horizon, but we’ll likely keep some of it all year round. The same is true for med ball training, plyometrics and yes, strength training.
But what I’ve noticed is that if I want an athlete to perform max effort med ball throws, for example, they have trouble doing so in a coordinated, sequenced and powerful manner, UNLESS, they have some strength work under their belt (or they are already strong to begin with...but that’s just luck of the draw). That doesn’t mean we don’t do med ball throws if an athlete isn’t strong, it just means that we probably can’t do max effort throws early on in their training cycle/career. The same is true when performing jumping activities, running and yes, even when doing technical work on the tennis court.
Like we saw in the image above, strength training will drive a lot of the other qualities forward. Think of it as a way to enhance those qualities to even higher levels, compared to what they would get to, without strength work.
As for as how early is early - I’ve started with 8 year olds in the past - a lot of isometric work at this age; but many of my mentors who have been in the field for decades have started Olympic lifting (and other lifting protocols) with kids that age (and some even younger than that…with no injuries to report).
3 - Will it Stunt Growth?
In some articulations, growth plates continue forming after an individual has passed puberty and has become a full-borne adult. Eric Cressey, in a previous article on this topic (which I will link at the bottom of this text), mentions that “the proximal humeral growth plate matures at about the age of 19, the distal (by the elbow) by the age of 10-14 and the clavicle (collar bone) matures between the ages of 22-25”! Given this, should we tell 21 year old seniors in college NOT to lift weights that may involve these joints? That would be silly wouldn’t it?
The reality is - and research has proven this time and again (see paper by Faigenbaum linked at the bottom of this text) - that strength training actually has a positive effect on bone maturation and development. We often forget that strength training doesn’t just affect muscles...it has an impact on many tissues...tendons, ligaments, fascia...and yes bones!
There has not been any longitudinal, retrospective and/or qualitative study which reported that strength training has affected bone maturation and growth in a negative capacity...not a single one.
Here’s Faigenbaum himself on skeletal growth/maturation...
“Traditional fears and misinformed concerns regarding the effects of resistance training on the immature skeleton have been replaced by scientific evidence that indicates childhood and adolescence may be the most opportune time for the bone remodelling process to respond to the tensile and compressive forces associated with resistance training. Weight-bearing activities, particularly resistance training, may actually be most beneficial during the growing years because the mechanical stress from this type of training may act synergistically with growth-related increases in bone mass. Adolescent weightlifters who regularly train with heavy loads have been found to have levels of bone mineral density and bone mineral content significantly greater than age-matched control participants.”
4 - Everything in Tennis is a Form of ‘Resistance' Training
Just so we’re clear, striking a tennis ball with a racquet is ALSO a form of resistance training. So is decelerating to a wide ball...and jumping + landing on one-leg when serving…
But we’re not concerned because the relative load is lighter (well kind of). In the case of a tennis racquet, yes, the racquet is much lighter than let’s say a 10lb dumbbell. Yet we might only do 20-25 total reps of a squat pattern with the 10lb dumbbell...compared to 300-500 strikes of a tennis ball…in one day! You see, weight training actually is a lot safer than playing tennis. In fact, I have not seen anyone get hurt from a strength program that was thought out properly and executed with safe progressions...but I have seen tons of players with shoulder, elbow, knee, hip, ankle, back pain (the list could go on) due to overuse.
5 - The Real Stress Parents Should Know About
Similar to point #4 above, parents often see their kids performing a bodyweight lunge, squat, push-up or pull-up, and they are totally fine with it. But did you know that there’s more load (and stress) placed on the body during a pull-up versus a dumbbell or pulley row for example? Think of it this way - a 12 year old might weigh 40kg, for instance - and when doing a pull-up, the majority of that weight is acting as the load during the exercise (both on the ascent and the descent). Now consider the alternative, a cable row with 20lbs - which one is heavier/more stressful on the body? I hope you answered pull-up! By the way, both are fine, just depends when and how they are implemented.
Here’s another example - I give a kid a 10lb medicine ball and ask them to perform goblet squats. I give that same child a 10lb dumbbell and parents are starting to ask questions. It’s the same load only presented differently! So why are we so concerned?
I could go on here...and even bring up some studies on force plate data (jumps elicit more force than loaded barbell activities in many cases...especially with the loads we use on kids during strength training).
Below is an Instagram post I shared a couple weeks back. This junior player performed what’s called a hang power snatch. It’s an activity that many athletes use to develop explosive/ballistic strength (an important quality in most sports...including tennis). I received a few messages asking why we were doing this and is it safe. Let’s take a closer look at this and present a few comments:
This was her 2nd time performing this activity, and considering that, her form was really really good
The bar is only 10lbs (yes you read that correctly). It’s specifically designed for kids!
We won’t go up in weight for a long time...but we can begin patterning the movement so that when she is ready, we can progressively add some resistance.
We don’t generally perform these movements with lots of load anyway - we perform them at loads that can be moved at certain velocities (but more on that in another post)
I have many years of experience both performing these lifts AND coaching them. I know what loads to use, how to progress the activity (or regress for that matter) and I know how to get an athlete to benefit from them.
Final Thoughts…
I was around 13-14 when I started getting interested in fitness. I was a good athlete but a late developer physically...and felt behind from that perspective as a youth. And I think the first time I read about a tennis player lifting weights was Pete Sampras - it was a feature in the Tennis Magazine (he was doing some lunges, presses etc...all under load). In any case, I still didn’t really know what I was doing as I didn’t have any coaching guidance but I’d still go to the gym regularly.
It wasn’t until university that I received my first strength & conditioning program...and my goodness did it make a difference in my game. Fitness became a strength of mine rather than a weakness. And as for my height...I was short for my age as a youth but a late bloomer on that front too. I had a growth spurt before university and actually continued to add some height to my frame until my early 20s. If anything, strength training perhaps helped with that rather than the opposite....but of course, I cannot be certain of that.
Lastly, there are many qualities that are important for an athlete to develop. So I’m not saying that strength should be prioritized over other abilities but I am saying that we shouldn’t be shied away from it. It can be an important part of a youth’s overall program.
For more on this topic, check out any/all of the articles below.
https://ericcressey.com/the-truth-about-kids-and-resistance-training
https://www.scienceforsport.com/youth-strength-training/
Citius, Altius, Fortius - Beneficial Effects of Resistance Training for Young Athletes
If you’re a parent, coach or player, check out my programs, HPP and HPS. On top of many qualities, players will gain strength/power...allowing them to track wide balls, hit with more speed and help stave off injuries in the process.