Apologies for 'reviving' this old thread, but I figured I could just add my experience here without opening a brand new one.
I'm a 31yo man with Bthal minor. I live in the UK but I was born and brought up in Italy; I inherited the thal trait from my father (who was born in the Po' Valley - just about the only spot in northern Italy where you get a nice cluster of thal minors
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Like some of you, I have been pretty asymptomatic for most of my life. I couldn't do cross country training in high school as I would get sick and breathless very quickly, but I was into sprinting, jumping, discus throw etc. I did some competitive cycling in my teen years but I performed very poorly. So i stopped
Last year I developed a passion for running. I started off running 3/4k, then over several months increased the length and pace. I live in a hilly town, so every run is hill training. I had a couple of injuries but nothing serious; however, when my runs crossed the threashold of 12k (1h) I started having bizarre symptoms that none of my friends had. It would take me ages to recover from cramps and aches (sometimes a whole week); I would often feel the need to sleep straight after a long run and more in general I would feel so fatigued that the rest of the day was a struggle. As I had been training and increasing the miles very consistently and progressively, I couldn't get my head around it. When I ran 15k I started feeling incredibly sick at the end, even if the pace wasn't 'extreme'; I had a massive bellyache (but not nausea, and I was able to eat a two course meal without problems). A 10 miles race knocked me out for at least 8 hours (and it took me 5 days to return to a slow, short run).
What have I done? I followed the advice in this thread and started working on my dietary intake. I monitor how much proteins, carbohydrates, fibres, vitamins and nutrients I get each day. I'm taking vitamin supplements. I ditched nearly all junk food (no crisps, no fizzy drinks, nearly no alcohol, etc.)I went to my GP and aked for blood test and make sure my vitamin D, B12 and folates levels are up to scratch. I did that 2 months ago.
I am feeling better. If I run more than 12/13k I need to make extra sure the pace is easily manageable. I litteraly have to slow down even when I feel I could be pushing, and that frustrates me, but I can feel the difference. If I push now (and I occasionally do, especially during a race)I know I'm going to feel sick, although not as badly as before. There is absolutely nothing else wrong with me from a health point of view, so I figured it must be the oxygenation. Which is likely due to bthal.
For fellows runner - lots of proteins and running on grass rather than asphalt has drastically decreased aches and pains. I still get them but much, much less. Friends who train with me say they don't notice a big difference if they run on pavement or grass, but I certainly do.