Conventional weight training, we are all far too familiar with, is based upon the principle of isolating muscle groups. Think of sitting on a leg extension machine. You sit, stationary, with your hamstrings (muscles on the back of your legs), glutes (rear end) and core (torso and back) supported by a bench. When you perform the exercise you move one isolated joint (the knee) along one plane of movement (forward and back) and activate a single muscle group (the quadriceps). The problem with that is you don’t move like that in the real world.
Imagine getting out of your car, sitting down at your desk, or bending over to pick up your child. You are going to activate that same muscle group you did while performing that leg extension. However, that muscle group is not going to be isolated and you are going to be moving more than a single joint on a single plane of movement. Muscles throughout your entire legs, feet, abdominals, back, shoulders, arms and neck are going to activate. Your ankles, knees, hips and spine are going to flex and your joints are going to move up and down and side to side in addition to forward and back.

Teaching your muscles to work together rather than isolating them is the principle behind functional fitness. Functional fitness exercises are designed to train and develop your muscles to make it easier and safer to perform everyday activities, such as carrying groceries, walking up a flight of stairs or even sitting at your desk. Functional training emphasizes getting more of the body involved in motions which includes multiple muscles and joint activities. If your muscle groups are not fully integrated and working in synergy strong muscles will stay strong and weak muscles will stay weak and you will create a pattern of compensation that can lead to a myriad of health issues, such as pack pain, muscle stiffness and joint issues. Functional fitness can not only make your daily activities easier but reduce your risk of injury and improve your quality of life in both the long and short term.