One of the many reasons for training is to improve how you move. A long standing method that has been employed in the past is standard static stretching. Many studies have shown that static stretching does nothing to actually improve actual movement or injury prevention. Often times flexibility can be improved without the strength to back up this new ROM, this ultimately makes the ROM useless.
This STUDY I found, but couldn't find the whole thing, showed that eccentric strengthening improved not only flexibility but strength and performance. I couldn't find what they were comparing, but this quote from the result.
"There was consistent strong evidence in all six trials in three different muscle groups that eccentric training improve lower limb flexibility, as assessed as using either ROM or muscle fascial length. "
Personal experience has shown that that static stretching doesn't change much as well. Getting stronger not just eccentrically, but isometrically tends to improve ROM. My two cents.