A study in 2008 shed light on the effect of exercise on men. 102 sedentary men between the ages of 40 and 75 were given a year long exercise program, while the placebo group where given no change in activity. The exercise involved both home exercises and exercises in the testing facility, it was based around moderate to high intensity aerobic activity for one hour for six days a week. They measured the levels of various hormones including testosterone,estradiol, free testosterone, dihydrotestosterone (DHT), 3alpha-androstanediol glucuronide (3alpha-Diol-G), free estradiol, and sex hormone-binding globulin (SHBG).
Happily most men stuck with the study only having two dropouts. DHT increases 14.5% in exercises while only increasing 1.7% in placebo at three months, it still stayed elevated by 12 months where it was at 8.6% vs 3.1% increase in placebos. SHBG also increased by 14.3% in the exercise group vs 5.7 in the controls. No statistically significant differences where see in 3alpha-Diol-G, estradiol, testosterone, free testosterone, or free estradiol between the two groups of participants.
The study indicated that increased levels of exercise lead to increased levels in DHT. DHT is strongly implicated in male pattern baldness, so it could be that this level of exercise could have an impact in hairloss. Of course this should be balanced by the fact that going exercise also have many positive health benefits, and that even though there is a link between DHT there are also many other factors involved.