My stress test was aborted when I hit 260/90.
I have alpha-1 antitrypsin deficiency. One of its effects is to increase the concentration of angiotensin converting enzyme in muscles, which means I'm supremely hypertensive when I give it full beans, so I'm not supposed to go flat out for too long.
I also get Raynaud's really bad in winter - the doc reckoned it's the same mechanism.
Generally speaking, walking and moderate cycling keeps my BP in check. If I go a few days totally immobile (like last week when I was in bed with a cold), it creeps up over the 140/90 limit, but only just.