I guess you could say I workout about 5 days a week. (I coach gymnastics everyday for 5 hrs per day) I usually straighten my hair every two weeks with the blowdryer using the pinkskates method or airdry using curlformers and then flatiron. I would say make sure that you take your time and flatiron in very small sections. That's pretty much key for me in keeping my bsl hair from reverting.
I'm not a "straight natural" but my hair is flat ironed right now. I keep it in 2 french braids while I work out and take it out in the morning. The waves hide some of the reversion at the roots. I work out about 1.5 hours everyday and I'm keeping my hair flat ironed for about 2 weeks.