Narrowing of the blood vessels carrying blood to the heart muscle makes the heart less efficient and increases the risk of heart disease. Numerous studies have reported smokers are more likely to have back pain and sciatica than non-smokers. Smoking reduces bone density, especially along the spine, which increases the risk of back injuries. Along with lowered bone density, smoking also impairs blood flow in bones and interferes with the production of bone cells. This results in slower healing time for bone injuries.
Smoking also reduces the body's testosterone production.
For strength training student-athletes this can have an adverse effect because testosterone stimulates the release of human growth hormone which needed for muscle production. The less testosterone available the less muscle the body is capable of producing. Smoking is harmful to all those around the smoker. Secondhand smoke comes from the end of a burning cigarette and from the smoke one exhales when smoking. Secondhand smoke is classified as a known human carcinogen, or cancer causing agent.