Warm up and preactivity stretching is done to alleviate tightness that might inhibit performance or movement. It is not done to improve ROM (range of motion).
Post exercise stretching can be done to improve ROM or just maintain current ROM. Individuals with good ROM stretch to maintain it and those lacking ROM stretch to improve it. Current ROM can be assess using a goniometer and compared to average or desirable ROM for each specific joint and movement of that joint.
Some activities require greater than normal ROM. Stretching to achieve this ROM can improve performance. But progressing ROM too quickly can be as dangerous as progressing weight training too quickly. And increased ROM often increases the likelihood of injury. This is one of the reasons that shoulder injuries are more likely than elbow injuries.
But the notion that “not stretching is OK” is becoming an “opinion” of many in the fitness industry based on limited research and often lacking scientific methods. If you have good ROM and live a lifestyle that includes movements that are essentially stretching which maintain this ROM, then no you do not necessarily need to stretch in addition to this. But if you find your ROM often makes it difficult or impossible to accomplish movements or tasks that you need to be able to do, then you would be wise to include stretching in your life.
Dynamic stretching as a PART of the warm-up process before active type exercise such as cardio classes, athletic events etc. has been shown to help reduce the risk of injury. I always have my clients perform some dynamic stretching before we workout since their sessions will include some dynamic movements.
I hope that this helps.
I too am old school when it comes to warming up and stretching. In aerobic/cardio dance classes the warm up is used to introduce any new choreography that you might be using and to increase blood and oxygen flow to the major muscle groups and joints. I also incorporate dynamic stretching in the beginning and then immediately after the cardio workout. I work with multiple generations and this sytem has served to avoid injury and to help participants understand the benefits of including flexibilty in their workout regime.
Static stretches do not increase core body temperature in and of themselves, so they don’t “warm” the body anyway, but having them in the warmup after you’ve done some rhythmic limbering, movement rehearsal, and perhaps some dynamic (not ballistic) stretching would be fine. Static stretches performed before a cardio workout aren’t going to be the problem that they would be prior to a strength or power workout, so no worries on that score. Static stretches done before power/strength exercise have been shown to reduce quadriceps strength by as much as 12%, and to negate the elastic energy created during the stretch-shorten cycle (this cycle is known to potentiate the body’s ability to perform at its best in activities such as vertical jump, etc.).