Shunting aside, exertion can lead to growth of bubbles from bubble seeds in the joints.
As the caps (ends) of two long bones flex hinge-like, or as one cap rotates in a socket, there are minute areas which momentarily* experience much lower pressure than the surrounding tissue. These low-pressure transients can allow microbubbles to expand to a size that triggers the inflammatory response that is thought to be part of the chain of events leading to DCS pain. This explains why joint pain is a common symptom.
The principle involved is "tribonucleation" which is also what causes cavitation on ship's screws when they're turned too fast. And it explains why strenuous exercise after diving is generally discouraged.
Compared to just sitting, some light exertion (walking, for instance) can increase blood flow throughout your tissues. Increased blood flow (perfusion) is good because it speeds up transfer of dissolved nitrogen from tissues to the lungs, where it's offgassed.
-Bryan
* using the word in its traditional sense of "for just a moment" rather than the airlines' sense of "very soon."