Katy:
If one were to be depressurized to altitude, I would definitely say that vigorous exercise is a bad idea with respect to decompression gas bubble formation. When it comes to scuba diving, we can only hazard a guess, since, to my knowledge, a study has not been performed.
The question is two fold. First, the musculoskeletal activity will definitely increase the number of tissue micronuclei. That is an experimental fact. These micronuclei will persist for about two to five hours again an experimental fact.
However, when one takes those nuclei and compresses them by diving, the answer becomes hazy since this has not been investigated. My guess would be that some nuclei would collapse by the pressure, but some would persist.
What is not known is the quantitative nature of the relationship. That is, just how much should the NDL be reduced, because one now has more than the normal concentration of nuclei present? The normal amount would be what we get from simply walking around. For us at NASA, part of our research involves this concentration since, in space, astronauts do not walk and the nuclei number is reduced.
The bottom line is that, I would avoid all strenuous activities for about four hours prior to scuba diving.:nono: