Norwegian University just released a study which analyzed exercise and it’s impact on fertility over a ten year span.  Researchers studied 3000 women and found that two factors were associated with increased likelihood of infertility:

1. Training every single day
2. Training to exhaustion (regardless of frequency and duration)

This turned out to hold true even after researchers adjusted for other infertility factors (body mass, smoking, previous pregnancies, etc.).

In fact, women who worked out every single day were a whopping 3.5 times more likely to have fertility problems.  Those who exercised everyday to exhaustion had the HIGHEST risk of fertility problems.

The good news is that these factors were reversible, so once training was reduced to more moderate levels (of frequency and intensity) fertility levels rose as well. 

Researchers believe that extreme energy expenditure of exhaustive exercise alters the body’s ability to maintain the normal hormone function essential to the fertility.

That said it’s important not to stop working out all together because good overall fitness is still important for general health, including fertility.  In fact, very low levels of fitness (and obesity) are also associated with conception problems.

Moderate exercise 3-5 times per week is probably fine and beneficial for most women, but every woman is different.  Women should be particularly concerned when their training is associated with missed periods, irregular periods or no periods at all.  Menstrual irregularities are a powerful indicator that hormone function is being negatively impacted by training.