human biology - What causes feeling of feet falling asleep to be delayed?

This answer explains the sensation of extremities "falling asleep" as a result of sustained pressure on a nerve. The answer links to an external web page that says that the feeling "quickly goes away once the pressure is relieved."

In my experience, however, it doesn't usually go exactly like this. For me at least, usually what happens is I will start feeling a tingling sensation in my feet after sitting in an awkward position for an extended period of time. If I ignore the sensation for long enough, it continues to get worse until I finally do stand up. But after I stand up, rather than the sensation quickly disappearing, I find that usually it suddenly gets much worse for a period of time. What started as an annoying tingling when I was sitting quickly turns into something quite uncomfortable upon standing up, even to the point where I am not able to walk around properly until the sensation passes a few minutes later.

But once I am standing up, the nerve shouldn't be pinched anymore, so why does the sensation of my foot being "asleep" remain for a few minutes after standing up, and why does it actually seem to briefly get worse after I have already stood up and "unpinched" the nerve?

Answer

This paper, while mainly dealing with chronic nerve compression, appears to explain the effects of nerve compression on the blocking the transmission of neural impulses (causing the "sleeping limb" syndrome).

This paper describes how the application of pressure on a nerve causes a miniature case of compartment syndrome, where the pressure causes the intraneuron pressure to increase, leading to paresthesia. Edema also occurs within the neuron, causing pain signals to be sent out. In the experimental rats which were unable to relieve this pressure, permanent nerve damage resulted.

When the effects from the nerve compression exceeds a certain level, the pain/tingling will result in you releasing the pressure from the limb in order to prevent nerve damage.

However, the nerves are still blocked from transmitting their impulses due to the compression blockage described in Paper 1. When the blockage is resolved, the neurons are now capable of transmitting their pain signals, which continue for a period of time until the pressure within the limb falls sufficiently below the pain threshold.