Do teens need strength or flexibility?

The teenage years are a remarkable time for athletic development, with so much potential for growth. As Physiotherapists and S&C coaches, we often get asked whether it’s more important to build strength or flexibility. It’s a great question – the interaction between strength and flexibility is probably the most underestimated performance boost for almost every teenager.

Is it better to be flexible or strong?

Some teens are genetically geared to build strength easier, while others have a naturally flexible body type. So which attribute is a better option for performance?

In the battle of strength or flexibility, part of the requirement is dictated by the sport. Ballet dancers require a lot of flexibility while rugby players are more inclined to strength.

But the truth is that strength and flexibility go hand-in-hand – they complement and enhance each other. Strength without flexibility, or vice versa, is not only prone to injury but is also limited in its performance.

Do you need strength to be flexible?

Flexibility is how easy it is for the body to move through range. It’s a result of connective tissue and muscle stretch capacity.

But while flexibility is the body’s ability to stretch, you don’t gain flexibility by stretching!

What makes a person flexible is improving the stretch capacity of muscles and connective tissue (tendons, ligaments, etc) by lengthening under load. While stretching alone doesn’t cause the muscle to adapt, adding resistance in that lengthened position will improve performance and flexibility.

Strength is equally important once you’ve gained flexibility. Being able to move through large ranges is great but you’ll be very injury-prone if you don’t have the strength to control the movement.

Can a stiff person become flexible?

Teenagers, particularly boys, see a rapid loss of flexibility around 14 years of age as their body grows. In addition, some families are just genetically predisposed to a lack of flexibility.

So can you gain flexibility if you’re prone to stiffness? The answer is a “yes” with a “but”…

Almost all body types can gain flexibility with the right exercise approach, although some bodies will adapt faster and better than others. For stiffer body types, this can be an ongoing “work-in-progress” that requires constant maintenance and effort. But it’s definitely possible.

Between a well-designed gym program and regular practice of sports or activities that require flexibility, even the stiffest body type can gain flexibility. But stiff body types will also regress to their natural level of flexibility if that stimulus is taken away – it’s something we see after holidays or injury.

Is strength training bad for teenagers?

There’s been a persistent myth floating around since the early days of gyms that strength training is a bad idea for teenagers. “Lifting weights stunt their growth” or “It’ll cause pain and injury”.

We’re not quite sure where these rumours started but we do know that plenty of research studies over the last 20 years have found the exact opposite.

Strength training helps performance and reduces injury risk. And while that might sound like a side benefit of lifting, think about the implications.

Around 30% of teens quit their sport involvement due to injury. That’s 30% of growing adult bodies that are moving towards a less active lifestyle and all the health implications of being sedentary. 

How much strength training should a teenager do?

We typically get asked how often teens should be lifting weights each week. How much is too much and what are the pros and cons of weekly sessions?

There’s a number of considerations here – are there training sessions and games for other sports in the weekly schedule? What’s the goal of training – improving movement or building strength?

First point: if strength training is added to benefit their main sport, it makes no sense to train so frequently that it leaves you tired for your main pursuit. This is something that is best decided in consultation with our trainers to figure out how often, as well as when, training can be best utilised.

Next point relates to the goal of training. Different goals have different training frequencies. Let’s go through each goal.

What’s the benefit of strength training for a 12 year old?

From the age of 12, the body begins to adapt to its stimulus with greater effect. So lifting weight will begin to build strength…but this isn’t the main goal.

At 12, the biggest benefit of strength training is to learn the techniques associated with lifting. These techniques aren’t just for the sake of the gym – it’s the same movements we do in everyday life and in our sports. Learning how to move and lift for the safest and best output is a key skill that serves them well as they continue to grow.

Can you build muscle at 14?

The magic age of 14 is when the body starts to ramp up its capacity to build muscle. Don’t get that mixed up with bulk though.

Building muscle capacity isn’t always associated with increased muscle size. Strength relates to muscle output and optimising that is the key focus.

From the age of 14, there is a golden opportunity to get a head start on the process and capitalise on the teenage body’s new growth potential.

Should a 14 year old lift heavy weights?

Heavy weights aren’t necessary in a successful gym program. At the age of 14, the muscle adaptations we’re aiming for can be gained at lower resistance and with different exercises, without resorting to heavy weights.

That doesn’t limit all 14 year olds from lifting heavy weights. Some teens naturally have the body type that will respond best to heavy weights. Other sports require heavy weights as part of their demands.

In these circumstances, it’s about the right lifting coaches sending the right messages that will build a successful program.

How many times a week should a 16 year old lift weights?

16 year olds have an even greater potential to respond to the strength program. But that doesn’t mean that more is better.

In choosing the frequency of a program, we need to consider other sports as well as adequate recovery times. There’s no point hitting the gym if you don’t allow your body enough time to rebuild itself afterwards.

As a general rule, twice a week is the minimum number of sessions to achieve a noticeable improvement in lifting capacity and movement quality.

This can be ramped up to 4-5 sessions per week but careful attention and monitoring is needed to watch for overuse injuries and over-training issues.

How much should a 16 year old lift?

Just because a 16 year old can lift more doesn’t mean that they should. The temptation for many 16 year olds is to out-lift the next guy, or to lift more than they did last week.

But the program goals need to dictate the plan – for example, if your sport requires speed, then lifting heavier (and slower) won’t achieve that aim.

So a 16 year old should lift as much as they need to in order to tick off their goals and improve their performance at their chosen sport. Because the overall goal is to feel and move better, not just chasing some number on a barbell.

Written by

Tim O’Grady

Tim is a Physiotherapist who specialises in football/Rugby and golfing injuries. Tim doesn’t believe that rest will make you a better athlete and he focuses on performance-based rehab methods. Tim is also qualified in golf biomechanics and injuries.

Bioathletic logo