Will running make you too tired for sex or will it increase your abilities?
In some ways, it can do both. Running can give you a nice physique which certainly doesn’t lessen your chances of attracting the opposite sex. In addition, you are in better cardiovascular shape which also can’t hurt! Running also releases endorphins and all of the other good chemicals into our bodies that make us feel happy and this is certainly not a bad thing either. However one of the drawbacks to running and your libido, is that rather than returning from a run exhilarated, many people may just come back fatigued and this can make love making unfulfilling or, in some cases, impossible. This not only has to do with fatigue levels but also the fact that testosterone in men and women is one of the main chemicals that increases sex drive and it is also used during running.
So at a certain point, if you're training is too intense, this may take away from your sex life. However, keeping training in balance with you and your partner’s sexual desires is just something that endurance athletes have to understand and deal with.