I have been wondering why I have felt sluggish and tired lately. Why my longs runs seem hard and my legs like lead. Then it hit me. I am Women. And just like this site states, we have different needs. After some surfing, here are some things that made me go "hmmmm"
http://www.runtheplanet.com/trainingracing/training/women/menstruation.asp
http://jogging-running-guide-tips.blogspot.com/2009/02/running-and-menstrual-cycle.html
http://www.articlesnatch.com/Article/How-Does-My-Monthly-Menstrual-Cycle-Affect-My-Running-/641687
http://www.runnersworld.co.uk/staying-healthy/30-things-every-woman-should-know-about-running/285.html
http://running.about.com/od/runningforbeginners/a/whatisrunning_2.htm
Hope these articles help you as they helped me. Happy running. :)