Let’s be clear: kids need to exercise. Whether it be through play, sports, or more organised training, it is extremely beneficial for kids to be active. Not only will it benefit them health-wise in the moment, it will also set them up to have healthy habits for the rest of their lives.
We’ll look into specifically strength training in youth, which can be a bit of a taboo topic for some as many fear it’ll stunt growth, or some other myth. In reality, strength training is great for the body as well as the mind, in the old as well as the young.
Be on the look out for our next blog post concerning aerobic training in youth.
Does Lifting Weights Stunt Growth?
As a parent of a child under 18, you might be wondering if the weight lifting your child is doing in the gym with friends or with a sports team is stunting your child’s growth. This has been a concern that has bothered many parents, but not to worry, your child does not have to stop working out. There’s actually no evidence whatsoever showing lifting weights will stunt your growth if you’re young!1 In fact, research has shown that lifting weights actually has plenty of benefits in youth, such as:
Increased muscle and bone strength
Decreased fracture risk and sports injury risk
Better grades in school
Better self esteem
We’ll delve deeper into these benefits later in this post.
Where does this myth come from then? Most likely it comes from the idea that weight lifting will damage the growth plates in children and adolescents. Now, doing anything irresponsibly can result in injury, whether it be lifting weights improperly and that are too heavy for you to handle, to roughhousing around on the playground, or even accidentally falling off a bike.
The growth plates are found at the ends of long bones and are cartilaginous areas that are soft and more susceptible to injury. Around 15-30% of all childhood fractures involve the growth plates.2 These plates harden into stronger bone when one reaches physical maturity. For girls this tends to be around the mid- to late-teen years and for boys mid-teens to early twenties.
But just because the growth plates aren’t fully developed doesn’t mean that you should avoid physical activity and strength training. Properly done, strength training can be extremely beneficial for youths. We’ll give some recommendations below, so keep reading!
Getting Stronger
One of the most obvious benefits of strength training is that it’ll make you stronger. Most people think of your muscles getting stronger, which is true, but that’s not all! Bones and soft tissues will strengthen as well!
Muscles … and Nerves
Let’s take a look at how muscles are affected. Now the physiology between a prepubescent child, a pubescent or post-pubescent teen, and a fully mature adult differs. In prepubescent children, strength gains are attributed mainly to neural adaptations rather than muscle hypertrophy (growth)3,4,5. This is shown through increases in strength without a significant increase in muscle cross sectional area that would indicate muscle growth.8 However, strength training does increase muscle fibre length and pennation angles that are associated with increases in strength.8 In contrast to older teens where greater muscle hypertrophy is seen, namely due to the increase in androgen hormones that come with puberty.
Let’s dive deeper into these neural adaptations. During pre-pubescence, children experience heightened neural proliferation and central nervous system maturation.4 Meaning, more nerves are being formed and new connections are being made in the body. When a nerve connects to a muscle cell, this is called a motor unit. One nerve may connect to just one muscle cell, or it could connect to multiple. The more connections a motor unit makes, or the more motor units are activated, more muscle can be activated and used. The more muscle being used means the greater the force output that can be generated.
What’s interesting is that strength training has been shown to increase this nervous system proliferation even more! Compared to youth who don’t participate in strength training, youth who did saw increases in strength and speed that can be attributed to increases in neuromuscular activation of the trained muscles. More precisely, increases in firing frequency of active motor units or changes in the motor unit recruitment pattern.6,7 One study found that more motor units were activated in the elbow and knee extensors in youths who underwent a 20 week resistance training program compared to youths who didn’t.8 Not to mention, while the activation of the targeted muscles improved, the opposing muscles saw less activation, which means the targeted muscles can work with less resistance and greater output!
Children who undergo supervised strength training programs have been shown to increase their strength by 30-50% after just 8 to 12 weeks!10,11,12,13,14 For instance, in one specific study, boys and girls between the ages of 7 and 12 who underwent 2x a week strength training saw significant strength gains in the chest press compared to kids of the same age who didn’t exercise.10
Increased strength can help improve certain athletic movements and skills, such as:
Long jump12,15
Vertical jump14
Squat jump16
30 yard dash15,16
Agility runs15,16
Some other papers have shown improvement in certain sport specific movements after strength training as well, such as:
Increased handball throwing velocity in adolescents17
Improved swim times18
Improved gymnastic performance19
Tendons
An often overlooked area is the tendon, the tissue that connects muscle to bone. Tendons undergo changes in composition and thickness following a strength training program, allowing them to tolerate more stress. One study looked at mid-adolescent volleyball players and found that their quad muscle was comparable in size to adult athletes, but their patellar tendon size was still significantly smaller.20 After following this group of volleyball players for two years, the patellar tendon of those athletes showed a growth of 27%21, suggesting that perhaps the ability of the tendon to grow is hindered up until the point when overall body growth rate declines. Meaning, mid- to late adolescence could be the period where tendon tissue mass can be built up by training until tissue turnover rate greatly reduces.22,23
On the other hand, early- to mid- adolescence could be a critical period of time for the tendon, as adaptations to stress seem to occur at a slower rate compared to the adaptations in muscle seen. This imbalance in muscle strength and tendon stiffness puts extra stress on the tendon tissue that puts the athlete at increased risk of tendon overuse injury at the onset of adolescence.24,25,26 It should be noted that more research needs to be done to understand these mechanisms better.
Bone
People reach peak bone mass between the ages of 20-30, which means that childhood and adolescence is the time to build up bone size and strength.27,28 Strength training is perfect for that! The extra stress strength training gives to the skeleton causes an increase in bone mineral content which is correlated with an increase in bone strength. It’s been shown that the longer you strength train, the better the bone strength index (BSI). Youth soccer players who strength trained 4 hours per week showed greater gains in bone mineral content compared to players who strength trained only 2 hours per week, and those who strength trained for 2 hours per week fared better than the soccer players who did no strength training at all.8
Another interesting aspect to take into account is that these bone adaptations can also be bone-specific. For instance, gymnasts and waterpoloists have been found to have increased BSI in their radius (forearm) while track and field athletes in their tibias (shins).8 Not to mention, better BSI scores are correlated with a decreased risk of fracture as well.8
Reduces Injury Risk
Along with the benefits already mentioned above, such as increasing motor unit recruitment, strengthening tendons, and increasing bone strength index (BSI) and bone mineral content, strength training also greatly reduces the risk of injury by improving the strength of stabiliser muscles during activity. Using free weights allows for multidirectional exercises that mimic the movements that occur during play and competitive sports. These multidirectional exercises require accessory muscles to kick in and help with balance, so strengthening these muscles can help prevent injury during high levels of exertion.29
One of the most often heard about injuries for athletes is an ACL tear. A well thought out and effective strength training program can help decrease the risk of ACL injury.30 It’s even been found that strength training combined with plyometric training in adolescent girls can help reduce the incidence of sport-related ACL injuries as well.31
Overuse injuries are quite common in athletes who perform repetitive motions - think of a baseball player that pitches dozens of times a game. Preventative exercise (or prehab as some like to call it) focusing on the muscle groups that are subjected to these repetitive motions has been shown to help reduce the occurrence of these overuse injuries. For example, strengthening the rotator cuff, scapular muscles and delts may help reduce shoulder overuse injuries in overhead athletes such as swimmers.32 Likewise, strengthening the quads and hamstrings can help reduce lower extremity injuries in American football athletes.33
Improved Self-Esteem
Adolescence is a time where teens usually feel awkward, might battle with mood swings and go through lots of life changes. An added benefit of resistance training is that it’s been found to improve global self-esteem and physical self-worth as well.34,35
Better Grades
We all know the stereotype of the bumbling meathead that’s dumb as a rock, but what if I told you the data suggests otherwise? A recent meta-analysis found that strength training makes kids do better at school. It looked at 53 studies and found that strength training improved overall cognitive, academic, and on-task behaviours in school-aged youth.36 In associative studies, muscular fitness was also positively correlated with cognition and academic achievement.
Mathematics was actually the subject that had the strongest relationship with muscular fitness, while languages and other scores provided less evidence. This could be due to the fact that concepts in maths have been shown to be associated with working memory37 - the ability to temporarily store and manipulate information - which has already been shown to have a strong association with fitness.38 Considering working memory is one of the main components of executive function, improving working memory may benefit planning, reasoning, and problem solving, all in all improving learning outcomes.39
In regards to this, adding resistance training during learning activities might be beneficial! This could be in the form of classroom activity breaks (anyone remember QDF?), intra-murals, weight lifting lessons during gym class or clubs! Body weight exercises like squats would be a good example as they don’t require any equipment, they’re scalable, and they’re a basic movement that’s suitable for kids and teens.
Recommendations
So, where should one start? Here are some things to consider.
Consider the Individual
Deciding whether or not to start a strength training program should be determined on an individual basis rather than just by age. Being able to properly follow instructions in order to learn proper form in the early stages is crucial for future success.
2. Start with the Basics
Even if you don’t have access to equipment, squats, pushups, and planks are great examples of exercises that work the major muscle groups and are fundamental movement patterns. You don’t need to copy some wacky exercise you saw some fitness guru do on instagram, or spend a fortune on a niche machine. Focusing on basic movement patterns will help build coordination, strength, and confidence, and those patterns tend to be the ones you perform in activities anyway!
3. Form is Key
In order to build good movement patterns and to get the correct muscles firing, form should be a priority. Have you ever seen someone squat with their knees all wobbly and back hunched over? How do you think that would translate over into strength or performance? Not very well.
If you’re just starting out, your squat might look like what’s described above - and that’s OK! We all gotta start somewhere. Perhaps regressing an exercise to an easier variation would help here, or starting off with just body weight, or perhaps a reduced range of motion. All these things make the exercise a bit easier. On top of that, practice. Practising will help you get used to the motion more and develop a bit more of the needed strength to perform it. This is where a fitness pro would come in handy (just keep reading)!
4. Be Patient
Improvement takes time. Whether your goal is strength, speed, getting bigger, or mastering a motion better, it takes time and practice. Just be consistent and stay focused!
5. Consider a Professional
Proper programming is key to any fitness endeavour, and it can be extremely beneficial if someone is brand new to exercising. From determining what exercises would be best considering the experience level and needs of the individual, to teaching proper form, to the appropriate volume, to how one should progress, when to progress, when to change things up - there are SO many variables to consider that can be overwhelming to someone who’s new to the space. Hiring a fitness professional (i.e. a kinesiologist wink wink) would be a great choice. Not only programming, a professional can also help with the above points too: helping with goal setting, tailoring the program to the individual’s needs, supervising during the workouts, enforcing proper form, and setting realistic expectations.
Our Goal and How We Can Help
Our goal at Delta Kinesiology is to help women of all ages reach their health and fitness goals. We specialise in conditions and injuries that women are more likely to experience, and we tailor the sessions using evidence-based principles and methods to help you reach your goals. Whether that be getting stronger, building muscle, learning proper form, or feeling better about exercising in general, we are here to help!
Check out some of the ways we can help below!
References
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