It is a myth that it is a rumor, and there are perfectly good physiological reasons to feel better after a Nitrox dive....but not everyone may be sensitive to the differences. The key to understanding the positive effect is that you are attempting to offgas during your ascent phase, even on a gradual, multilevel ascent. That offgassing is MORE efficient if you are breathing Nitrox, because each breath has less Nitrogen in it than it would have if it were air, so the offgassing gradient is more favorable. The tables do not take this into account; they assume the only effect of Nitrox is less on-gassing compared to air. The off-gassing advantages of Nitrox are just not part of the calculations. It is a small effect, most apparent after a series of dive, especially deeper, longer ones, and manifests itself as keeping you farther away from "subclinical DCS," a.k.a. a feeling of tiredness after a dive. I can provide no citations to this explanation, but I am confident they will appear in time. There are just too many people experiencing the effect for it to be ignored.@Francesea that rumour has evolved from people diving nitrox as if they were on air so they have less nitrogen loading. If you dive nitrox to the NDL's then if you feel different it's a placebo since you have the same theoretical nitrogen loading in your tissues