I would guess a bit of both. Less coincidence than that’s just how starting a new exercise program works, combined with PTSD reacting to stress the way it does.
Exercising after not having done so? Creates a LOT of low-level pain/soreness/toxins that need to be flushed out, that our body isn’t used to flushing out, and mineral/salt deficits (Calcium & Potassium in particular) we’re not used to replacing.
So even if we drank twice as much water as usual, AND ate a banana (postassium for muscle relaxation), AND something calcium rich (for muscle flex, or be prepared to be exhausted, it takes way more energy to take calcium out of our bones to send to our muscles, than to take it out of our bloodstream), AND ate protein (for muscle repair)? We’ll still probably have a headache, sore muscles, and feel exhausted & crappy… for a couple of days. x1000 if we didn’t actually increase water, potassium, calcium, & protein intake.
Pain? At any level? Even low level “I’m not used to this” exercise soreness? Increases anxiety. Because that’s just how pain works.
Whilst exercise reduces stress (in no small part by burning off all the chemicals swirling around in our blood saying fight/flight), the sudden LACK of that normal high stress living? Plus Pain? Creates a lurch, a gap, where the sudden lack of OMG! creates a rebound OMFG!!!
AKA
Drink water, hit up the potassium & calcium rich food sources (or drink a Gatorade), up your protein, drink MORE water… and keep exercising. Even “just” stretching and moving around… And I would expect you to feel better very shortly. As in better than before you started jogging.
Beginnings? Can be rough.
Even just taking a few days off, or trying something new in the middle pf an established routine, nearly always creates the “I feel AWFUL!” for a few days, up to a few weeks. But as long as we’re supporting our bodies (giving them the increased nutrients and water they need), it’s usually very short lived. Just not as short lived as anyone I’ve ever met (from pro athlete to couch-to-5k) would like!