Testosterone and Running

A good bit of research shows that long-term endurance training is associated with lowered testosterone levels.  There is much less research showing the effects of sprint training on testosterone levels.

However, I did manage to find a short study on this:  Journal of Sports Sciences, Vol. 23, Issue 2, February 2005, pg. 187-188 (no abstract).  Here they compare testosterone levels among different groups of males:

• Sprint Trained -   9.11 (ng/l)
• Endurance Trained -   7.05 (ng/l)
• Sedentary -   8.19 (ng/l)

Since this data is a cross-section, it does not establish cause-and-effect.  In other words, it's possible that men with low testosterone self-select into endurance running, and men with high testosterone self-select into sprint running.  However, this data is very suggestive that sprint training may increase testosterone in men.