A lot of people think mobility and flexibility are the same thing, but that’s not quite accurate. Mobility refers to moving actively through a range of motion. Flexibility refers to passively lengthening through a range of motion. Flexibility is one piece of the mobility puzzle.
There are many components of mobility, including flexibility. If the muscles or passive structures (ligaments, joint capsules, etc.) can’t stretch enough to allow movement, then you will have limited flexibility and mobility. Important to note, if you have a stiff joint capsule, all the muscle stretching in the world won’t help improve your mobility. Strength and motor control are also key features of mobility, but we’ll discuss that later.
Joint range of motion is one of the most important parts of mobility. Every joint (except the scapulothoracic joint, but that’s not a real joint anyway) has a joint capsule. Think of the joint capsule as heat shrink surrounding your joints, except when it is not stretched and moved around it starts to shrink (as opposed to when heated). This is important because when you move, your bones don’t just roll in place, they actually glide as well and push into the joint capsule. If the capsule is tight and does not allow the bones to glide properly, movement will stop. This is fairly common and typically presents as a feeling of locking or pinching in a joint when you are attempting to feel a stretch in a muscle.
As I said earlier, mobility is the ability to actively move through a range of motion. This means we also have to take into account motor control and strength. Motor control is being able to control active movement throughout a range of motion. Think of someone who hasn’t been able to reach overhead fully for several months. If they only stretch their arm overhead passively they won’t have the strength end range to move into it actively. Their muscles and other structures might have the flexibility to get there, but the person doesn’t have access to the range actively because they don’t have the strength. They might be able to lay on the floor and have gravity pull their hands down to touch the ground overhead, but can’t get in the same position standing, when gravity is against them. This means their mobility is poor, even though they have the flexibility.
So how can you use this information? If you are unsure if you need to work on flexibility, mobility, motor control, or strength, then I would do a combination of them all. Flexibility is the bottom of the totem pole. You want to make sure you have the ability to passively move through motion. Start to add muscle contractions at each end of a movement. For example, if you are stretching your hamstrings you could use a door frame to aid in the stretch and you can isometrically push your leg into the door frame at the top of the stretch to activate your hamstrings. This is very similar to contract-relax PNF stretching commonly done in sports. To take things one step further, once you finish stretching your hamstrings you can perform several sets of leg raises where you slowly (and actively) move your leg through the full available range of motion. Combining passive stretches with motor control and active exercises, you are more likely to benefit from your mobility efforts and achieve your desired results.