This is just one study of many looking at sports and injury prevention. With every study the findings are slightly different and since each study examines a different segment of the population, my advice is to always take each piece of new information in stride.
This study, for example, examined 3,000 long-distance runners and found that they were more likely to get hurt if they were overweight or switched routines, but stretching before or after exercise didn’t appear to matter. This group, overweight or not, was obviously very active and in decent shape, since they were all categorized as “long distance runners.” Regular exercise naturally stretches your tendons and muscles and gets them used to moving and extending.
However, if you are a weekend warrior who has never seen a yoga matt and you do no exercise all week long then that Saturday morning run is more likely to result in injury. If you are a weekend warrior, then you would likely benefit from a warm up and a good stretch before you embark and after you return.
And everyone, whether you are in great shape or not, participating in activities that require a lot of sudden stops and starts like soccer or basketball would also benefit from a warm up and a stretch.
Stretching is an important component of overall health and flexibility. People typically start to lose flexibility and become more prone to injury as they age simply because they become less active and more sedentary.
The good news is that flexibility lost can be regained. Yoga is surprisingly not difficult and people of all ages, activity levels, and flexibility can participate and benefit from this type of stretching activity. But, if you work out regularly and incorporate activities like yoga into your fitness routine, then stretching before or after running or other aerobic exercise likely will not make you more prone to injury.