Hormones Affect Hair...

Hormones from stress or exercise can help or hurt your hair. Stress produces hormones. One of them is Cortisone. A hormone that is secreted by the adrenal gland. This hormone stops hair follicles from growing leading to thinning of the hair. Moderate exercise helps in producing serotonin and endorphins. These hormones help the body in dealing with stress.
DHT which means dihydrotestosterone is a hormone that can also cause hair to thin. If DHT levels are allowed to rise then this slows the growth of new hair cells, causing less hair growth. Slow steady exercises like jogging or yoga can help in reducing the formation of DHT.  However, over exercising once in a while can produce more DHT. So, always try for moderate to exercise.