Weight training is not a one size fits all, there are many different ways you can train your body to achieve different goals. Your goal could be strictly aesthetic, it could be rehabbing from an injury or simply trying to move better.

 The way you train will dictate the results you get. For example, running marathons will most likely never make your legs look like tree trunks. The same way, doing leg extensions on a machine will help you get those huge legs but it won’t teach you how to perform a super deep squat. 

Every style of training is geared towards achieving a specific goal. Bodybuilding is the art of training with the only goal of achieving a certain aesthetic, namely big muscles with a minimal body fat percentage.

 On the opposite functional training is the art of training your body to perform movements and improve its mechanics.

Bodybuilding focuses on training muscles. That means when a bodybuilder needs his biceps to be bigger, to achieve his ideal physique, he will go on and specifically train his biceps by performing isolation exercises targeting his biceps only. Performing a wide variety of bicep curls will without a doubt stimulate your biceps to grow and get stronger but it won’t help you improve your motor capabilities much. Apart from using isolation exercises, bodybuilders also use a lot of machines to perform their exercises. The advantage you get when using a machine is that it removes all the challenge of stabilising the weight. The load being totally stable enables you to generate more force on the load. This is a principle in training, the more stable you are the more force you are able to generate. Imagine performing a squat on a level floor compared to doing it standing on a bosu or an uneven surface, it’s pretty safe to say that you would lift a lot less standing on a bosu. The other advantage of reducing the stabilisation demand of an exercise is to target a muscle better. When I'm training with free weights, my whole body might be working to stabilise the load while I'm performing the movement. This can make it difficult to feel the muscle I want to target, making it hard to push that targeted muscle to its limit. We can see now why bodybuilders train that way, they want to create the biggest muscle growth stimulus in the most efficient way. This way to train is great to become more muscular but has many drawbacks in term of improving other areas of your fitness.

On the other hand, functional training’s goal is to teach your body to perform movements. This means that you are gonna measure your progress with more than the mirror or the scale. If for example I'm unable to perform a bodyweight squat, the goal of my training would be to improve my ability to squat. Depending on the reason why I can’t squat, I could use mobility drills, technique work, or use an exercise modification that will eventually get me to squatting. The muscle mass you can gain by training functional is more of a byproduct of you getting better and stronger with the movements. Those movements will normally be challenging your coordination and ask the muscles to work as a team. Machines are not really used in functional training for that reason : it doesn’t challenge your coordination enough. The equipment used is normally either free weights or your own bodyweight. Functional training sees fitness as something with several dimensions that all need to be developed. It has much less drawbacks when it comes to improving your general health but at the same time will give less specific results. Given that most people that go to the gym do it primarily to exercise and to get healthier, this way of training is perfect for the general population.

Are those two ways of training mutually exclusive? Not at all. Functional training won’t make you look like a pro bodybuilder but it will certainly help you build all the muscle mass you want and get an athletic physique. Same thing for bodybuilding, most bodybuilders include functional exercises in their training, it’s those that don’t that are caught lacking in the department of coordination and body control. Chasing aesthetic gains before learning how to move is like repainting a car that needs a new engine. That wouldn’t make sense right? Well the same goes for your body.