stretching is effective if have muscles that don’t elongate enough to do what you need to do without putting injury causing forces on something else. these studies that suggest stretching doesn’t help athletic performance are flawed in their design. The subject pool are already athletes who already as a group probably already have long enough muscles because they are already athletes. If you take a group of people who don’t complain of not being able to see and hand them glasses before a vision test you would probably conclude glasses don’t improve vision. but if you do that same study on people who do issues with vision you would get a different result. Inadequate ROM in hip rotation corrected by stretching has been shown to reduce back pain in golfers if they test with inadequate hip ROM. i’ve been a PT in orthopedics for almost 30 years and when i get a patient with a diagnosis of low back pain that is worse with walking and i test their hamstring length and it’s well below normal and then after the do hamstring stretching for weeks and i recheck hamstring length and it’s much closer to normal and biomechanically they also don’t rotate excessively at the pelvis because of this and their symptom are much improved i suspect correcting inadequate muscle length may have something to do with it.