Dear Readers:
Post dive exercise
I might estimate the waiting time between a dive near the NDL limits and a climb up a big hill with gear as about 30 minutes to an hour. As with everything in diving (that concerns gas loading), conservative is better than liberal. Exercise and depress was studied as a part of NASA research concerning EVA (extravehicular activity), and the abstract is given at the bottom of this post.
How Much Exercise is Bad?
One problem with all of these recommendations is that they are hazy. In the laboratory, exercise is determined by oxygen uptake measurements. That is not possible in the field with the recreational diver. Additionally, every situation will be different. Gas loading and unloading is easy to estimate by calculation (Haldane did it one century ago). While the exact amount is not known for each diver, nitrogen loads can be guesstimated and a plan worked for maintaining safety in a multiplicity of dive scenarios. Stress-assisted nucleation (bubble formation) in supersaturated divers is difficult to judge. 
Microbubbles must be kept in check or the gas exchange situation runs amuck. The two-phase systems (gaseous nitrogen in bubbles plus dissolved nitrogen in tissues) are only manageable when gaseous nitrogen is kept at a minimum. That is why profuse bubbling is bad in multidiving situations. Bubbles in tissue modify off gassing and bubbles in capillaries modify off gassing AND blood flow.
The situation given above by Uncle Pug indicates that he believes that his initial dive started the down hill slide towards bubble formation
Gentle Exercise
Braunbehrens commented that he thought he heard that gentle exercise was harmful. Actually, research indicates that gentle exercise during the deco stops is a good activity to promote blood flow and washout.
Dr Deco :doctor:
Please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm
Dervay JP, Powell MR, Butler B, Fife CE. The effect of exercise and rest duration on the generation of venous gas bubbles at altitude. Aviat Space Environ Med 2002 Jan; 73(1):22-7
[Medical Operations Branch, NASA-Johnson Space Center, Houston, TX 77058, USA.]
BACKGROUND: Decompression, as occurs with aviators and astronauts undergoing high altitude operations or with deep-sea divers returning to surface, can cause gas bubbles to form within the organism. Pressure changes to evoke bubble formation in vivo during depressurization are several orders of magnitude less than those required for gas phase formation in vitro in quiescent liquids. Preformed micronuclei acting as "seeds" have been proposed, dating back to the 1940's. These tissue gas micronuclei have been attributed to a minute gas phase located in hydrophobic cavities, surfactant-stabilized microbubbles, or arising from musculoskeletal activity. The lifetimes of these micronuclei have been presumed to be from a few minutes to several weeks.
HYPOTHESIS: The greatest incidence of venous gas emboli (VGE) will be detected by precordial Doppler ultrasound with depressurization immediately following lower extremity exercise, with progressively reduced levels of VGE observed as the interval from exercise to depressurization lengthens.
METHODS: In a blinded cross-over design, 20 individuals (15 men, 5 women) at sea level exercised by performing knee-bend squats (150 knee flexes over 10 min, 235-kcal x h(-1)) either at the beginning, middle, or end of a 2-h chair-rest period without an oxygen prebreathe. Seated subjects were then depressurized to 6.2 psia (6,706 m or 22,000 ft altitude equivalent) for 120 min with no exercise performed at altitude.
RESULTS: Of the 20 subjects with VGE in the pulmonary artery, 10 demonstrated a greater incidence of bubbles with exercise performed just prior to depressurization, compared with decreasing bubble grades and incidence as the interval of rest increased prior to depressurization. No decompression illness was reported.
CONCLUSIONS: There is a significant increase in decompression-induced bubble formation at 6.2 psia when lower extremity exercise is performed just prior to depressurization as compared with longer rest intervals. Analysis indicated that
micronuclei half-life is on the order of an hour under these hypobaric conditions.
