When muscles are tight we have a natural impulse to stretch. But did you know that tight muscles are usually weak? They lock in place (tighten, shorten) to either meet the demands we place on them or if, like our buttock muscles, we sit on them all day and never use them, they will weaken (shorten) from underuse. Try as we might, stretching will only have a temporary effect on them.
Let’s look at the hamstrings, the muscles at the back of the thighs, as an example. People I see with low back pain are often tight in the hamstrings and weak in the glutes (buttock muscles). Studies show that the brain inhibits the use of the gluteal muscles with back pain. So the hamstrings compensate for them and become overworked. They lock in place to meet the demand.
No amount of stretching is going to change that; instead we need to strengthen the gluteal muscles (the buttock) and mobilize the hips. Then the hamstrings will start to relax and stretch.