I found this to be a really interesting question, so I googled, because I now wanted to know! It's OK to exercise while TTC but dont over stress yourself like Mrs WKJ said, because it could delay ovulation since your body may be telling itself "oh no, i'm stressed, not optimal time for conception". BUT the study also said that if your BMI is 25 or under, vigorously exercising could delay conception, while if your BMI is above 25, vigorous exercise could help conception. Very interesting.