As you perform daily life activities like squatting, walking, running, and jumping, muscles work together in coordinated movement allowing you to perform these tasks with ease.
The coordinated activation of muscles happens at a subconscious level. Movement, on the other hand, can be brought under our conscious control. Therefore, conscious retraining of dysfunctional movement patterns is a great starting place in improving functional strength or the strength that supports these whole-body movements outlined above.
What is strength?
Strength is the ability to apply a force to oppose or support a load. It is a function of how muscles and tissues work together rather than just the contraction of one. It requires precise timing and grading of muscle activity, both in terms of the percentage of maximal contraction and how the muscle is working.
A muscle has several ways that it can perform. Here are three types of muscle activation.
1) Contracting or Shortening
A type we're most familiar with and the one we're most likely to do at the gym (e.g. lifting a load). Since it involves shortening, the muscle will increase in size -- something many people train for in the first place.
2) Isometric Contraction
While being able to lift things is essential, other types of muscle performance are equally as important. A muscle can also work to hold a position, which is called an isometric contraction. An isometric contraction is useful in applying tension to the fascial net and helps to provide support.
Active lengthening activates a muscle to lower a load or, more commonly, support us relative to gravity. This type of training is often associated with long, lean muscle development.
While discussing the different ways a muscle works is simple, it's a very complex and unconscious process that is impossible to control consciously.
How we gain control.
We can start by supporting our bodies as we move through various functional positions, progressing to loading the body by adding some weight. Furthermore, we can break more complex functional activities, like walking, down into their component movements. In doing so, we can train to ensure the proper support of those movements and gradually integrate them into the whole-body movement.
Ultimately, we need to emphasize the development of proper movement strategy to establish appropriate muscle development. Improving your functional strength will broaden the activities that you can safely participate in and optimize your performance in those activities.
Increasing the mass of one muscle will not ensure that it's working in coordination with other muscles. Likewise, the volitional activation of a muscle resulting from a cue to "pull the navel in" or "engage your core" doesn't ensure the proper activation. Neither option guarantees functional support in terms of intensity and timing (Women's health, the Pelvic Floor Paradox and a Naturopathic Approach).