"What's a good stretch for this?"
This usually comes from someone that's got a small niggle somewhere on their body.
My answer is always "first of all, what did you do to it?"
Stretching is not the magic pill that fixes all injuries. Sometimes it'll actually make the injury worse - especially if that injury occurred from overstretching in the first place.
One of the most common things I see is people trying to stretch their low back to reduce stiffness. This'll give you temporary relief from discomfort because you're stimulating the receptors deep inside the muscle. But that stiffness will come back with a vengeance because you haven't fixed the issue.
Side note: if your low back feels stiff. Stretch the hips instead. The low back is designed to be stable. When the hips are tight the low back will act more like a "mobile" joint. This can cause pain and stiffness. So next time you have low back tightness you could try these 3 stretches for 1-2 minutes (on each side - where appropriate). YouTube is your friend here. Obviously if you have a serious injury, don't do these stretches and speak to a physio/expert.
3-Seated figure 4
While stretching may be useful in some scenarios, you'll likely feel better with an active recovery. The soreness you're feeling is usually the result of inflammation. We need inflammation to help deal with the injury. The goal inflammation is to attack the injury site with a bunch of chemicals, white blood cells and immune cells. But we don't want inflammation to hang around for too long.
Creating a muscle