Once the research overwhelmingly demonstrated that trying to improve an athletes flexibility was actually a net negative, that’s when mobility came to the forefront
Mobility is defined as the ability to move unimpeded through an intended range of motion
To perform mobility, you’re typically using body weight or very light loads to work on movement patterns
Athletes found that not only did mobility work help them to feel better, but also improved performance, to the point that a debate actually arose as to whether an athlete should focus their training around speed and power, or mobility
However it’s not binary. An athlete should be working on both strength and mobility.
In fact, mobility is heavily reliant upon strength, because when muscles that surround a joint are weak, they become hypertensive and they lock down the joint.
So often what an athlete needs to improve their mobility, is improving their strength.