Hi Laura01,

it always the same problem with stretching pre or post exercise. There are so many different opinions out there. I think, that as long as a joint has full ROM there is no need of stretching before exercise. Better is a proper warm-up regimen, where active stretching occurs, because joints are moved throughout a bigger range than in daily life. Often stretching is practised for a long time by an athlete, so kind of mental preparation might be a reason for stretching. And also you have to hold a stretch for approx. 30 sec to get any effect (better is up to 90 sec.) most athletes are stretching for a couple of seconds, which is more or less a mental thing.
But after exercise stretching is important regarding to cool down and injury prevention. During stretching a muscle relaxes (because Actin and myosin fillaments are pulled appart), during exercise it happens in eccentric action but not that much. It also helps the cardio-vascular system to calm down.
My advice would be to develop a good warm-up program, where joints are moved actively through there full ROM, sport specific moves etc. and also a good cool-down program including gentle jogging, stretching etc.
My own experience is, that i never stretch prior to exercise, but do a proper warm-up and also cool-down. And I never had any muscular injuries.
Good luck Wutti