So many interesting contributions!
Nightingale, I did HIIT a few times in the last couple of months (20 min of biking at the gym), but at the end I was so exhausted, and my heart was beating so fast (over 160), that I couldn't pursue on with my hour of weight lifting. Would you recommend that I sometimes do the HIIT for a longer period of time, without the subsequent weight lifting?... I read that HIIT was great for people who want to lose weight, though (that's not me), because of the high intensity and because you continue burning calories hours after the exercise is over. You seem to have had a different experience, however. BluesBrother, have you been losing or gaining weight with HIIT?
It's interesting to note that sports seem to have helped at least a few of us with their POIS. BluesBrother, from what you said I understand that your POIS symptoms appeared after you stopped doing sports at a semiprofessional level. Several in this forum have reported that their symptoms started at around age 16-17 (I think it was around 20 for me), though, which is the age you quit semiprofessional-level sports... So, I would say that it was probably just a coincidence, but I guess I could be wrong.
Now that we have established that sports help at least a few of us in a significant, positive way, I would be very curious to know why and how! Is POIS weaker if your heart is stronger? Does it have to do with oxygen circulation, or the release of hormones or other substances during physical activities that would prevent the symptoms to appear? In my case, the combination sports/fenugreek has been a good one. What do fenugreek (or niacin) and sports have in common in terms of physiological effects?
To those who have said POIS tire them too much to engage in physical activities, I would suggest to try to sleep better (as Prancer noted, sleep is also important!) while refraining from ejaculating for a while. Then start doing some cardio 15 min a day. You will feel definitely better. After 2-3 weeks of that you can try having an O and see if the cardio has had a beneficial impact over your symptoms. It much harder to do the cardio when in POIS, so you have to initiate a virtuous circle, first. Also, don't forget to drink a lot of water! it enables your body to function better at all levels.
Cheers