Do you stretch? Do you have mobility exercises?
Stretching has it’s place, but most mobility is determined by the nervous system.
Sometimes, sensory input HOLDS the body in its desired position, even if that position is a compensation or suboptimal for biomechanics; the brain evaluates it as optimal given every input.
For example, my teeth look straight, but I have to shift my jaw to maximize my jaw stability. This demands extra tone in my head and neck, which then leads to my hips shifting to the right and recurring headaches.
Once I got fitted for a dental orthotic to help fix my jaw shifting, my headaches decreased from 1-3 / week to 1-2 / month.
Any sensory system can hold you in these compensatory positions. Most of the time, the people I train are used to lifting or moving a certain way. They just need to be reminded of another way to move, then they need to reinforce those movements. This can increase mobility instantly.
Resources
Stop Stretching, You’re Wasting Your Time – Here’s What to do Instead
Here's an example of joint positions restricting mobility. I walk through some exercises with my friend Jess and his hip flexor tightness goes away.
Kettlebell Pullover
Watch Cody's shoulder mobility increase after a relatively simple ab exercise.
Auditory Influences on Joint Mobility
The ears can restrict you, too. Watch Brandon's hip mobility increase after putting in one earplug.