Injury
Impotence, also known as erectile dysfunction, occurs when a man is unable to maintain an erection long enough to have sex, according to the Mayo Clinic. When an erection is achieved, a process must take place. Two, sponge-like chambers, the corpus cavernosum, fill with blood from nerve impulses that are sent from the brain during sexual arousal. The penis becomes erect as a result. If the nerves next to the penis are damaged, impotence can occur. This can happen through bladder or prostate surgery, or it can occur if the pelvis, spinal cord, penis or prostate were injured.
Underlying Diseases
Chronic health conditions that effect the nerves, arteries, veins, heart, liver and kidneys also can cause impotence. Examples of these health problems include high blood pressure, atherosclerosis, heart disease, multiple sclerosis, Parkinson's disease and diabetes. Another cause, hypogonadism, occurs where the male sex hormone testosterone is not being released at adequate levels.
Medications
Medications that are prescribed to treat another medical condition might also cause the unwanted side effect of impotence. Examples include tranquilizers, sleeping aids, antihistamines, antidepressants, high blood pressure medications and appetite suppressants.
Lifestyle
Regular use of legal as well as illicit drugs, such as marijuana, alcohol and tobacco, can cause impotence. For example, smoking causes the blood flow through the veins and arteries of the penis to be restricted, which can lead to impotence.
Obesity
Obesity raises the risk for a number of conditions, such as high blood pressure, diabetes, depression, stroke and impotence. According to the Mayo Clinic, men who are obese are more likely to suffer from erectile dysfunction than normal weight men.
Psychological Factors
In order for an erection to occur, the body must be relaxed and aroused. This process starts in the brain, so if you are suffering from certain psychological factors, including depression, anxiety, guilt, stress, fatigue or low self esteem, impotence can occur.
Pressure
Bike riding is a cardiovascular exercise that is safe for the joints, because there is no impact. But biking also puts pressure on the nerves and blood vessels that are responsible for blood flow to the penis. As a result, excessive bike riding can lead to temporary impotence.
