The terms flexibility and mobility may sound like they’re the same but they’re actually different which means that there are different ways to work on these aspects in an exercise program.
When you work on flexibility, you are working on stretching your muscles. This means that working on flexibility works on creating length in a muscle. The act of stretching and working on flexibility is passive.
The term mobility refers to how your joints are moving; it’s about the ability of a joint to actively move through it’s full range of motion. Mobility is more dynamic meaning it takes into account everything, so to have good “mobility,” you need to have adequate flexibility, strength, and stability. You need adequate flexibility so your muscles can lengthen enough for your joint to move easily through it's full motion and you need adequate strength and stability to keep your joint stable so it can move smoothly.
Flexibility is more passively working on motion and mobility is more actively working on motion.
Here's an example of the difference between the two:
If you lay down on your back and hug one knee into your chest, you're working on flexibility. This is because you are using your hands to pull your leg into your chest so this is passive. If you perform the same movement but leave your hands out of it and just work on using your muscles to bring the leg in towards your chest, you’re working on mobility. So even though both examples are moving your hip joint in the same direction, one is more passive so it works on flexibility and one is more active so it works on mobility.
Poses found in a vinyasa yoga class can work on both flexibility and mobility. This is what makes movement based yoga practices so beneficial for the body. Just by practicing vinyasa yoga, you can work on strength, flexibility, and mobility which are all important to keeping the body in balance.