I would have to concur with Andy. I also crash after a certain point unless I am in good aerobic shape which is no longer the case. I used to bike for hours but the first 45 minutes were terrible. After that, as long as I could stay hydrated and shove carbs down my throat, I was able to go for longer than others. Oxygen carrying ability is altered in thal minor so it is possible to figure out how to optimize things. These days, I work out one day per week doing Pilates with a personal trainer for one hour and although my muscles get targeted and worked hard, I don't feel dead. If I don't eat a small snack that has some carbs and protein withing an hour of my workout, I get the shakes halfway through my session and that sucks. Thankfully this has really helped my injuries and the overall definition of my body is an added plus. I can't afford time or money for more right now. It also makes a huge difference for me to take my iron+b's and c's syrup (Floradix) right after my workout. You lose iron with exercise, the b's help the blood regenerate and the c's keep my immune system level which can drop from exercise for a short period during the workout. Also, I workout in the afternoon/evening because if I do morning, I feel totally flat mentally for the rest of the day.
If I go to the gym, I seem to get perky when everyone else gets pooped but when my crash comes, it is bad. I frankly don't think that is necessary. After all, longevity depends upon a slow and economic metabolism. I find that many fitness plans emphasize jump starting your metabolism and all that, but in reality you just need to cut the bad fats and carbs when you won't be using them right away and add more activity that doesn't have to be super vigorous. If you add a simple muscle building plan with light resistance training instead of heavy weights that bulk you up, your body will burn more calories. But exhausting yourself to burn calories is not a viable strategy for thals. Maybe for someone with an HB of 14-16 and nice fat blood cells...someone like my boyfriend who can kill himself at the gym and still get up the next day and not feel like he needs 15 more hours of sleep...
And then there is the terrible thing that I have that if I manage to survive a long day and catch my seconf wind, I can work several 16 hour days with 6 hours of sleep in between and not crash for awhile. I can pull that off for about a week and then my brain turns to mush, but in times of crunch at work, the Marientina-stealth mode seems to still work although I attribute my increasing gray hairs to the increasing frequency of the long work days...