Bodybuilding Pose

Some bodybuilders use drugs such as anabolic steroids and precursor substances such as prohormones to increase muscle hypertrophy. Most of the substances require medical prescriptions to be accessed legally. Anabolic steroids cause muscle hypertrophy of both types (I and II) of muscle fibers caused likely by an increased synthesis of muscle proteins and are accompanied with undesired side effects including hepatotoxicity, gynecomastia, acne, male pattern baldness and a decline in the body's own testosterone production, which can cause testicular atrophy. Other controlled substances used by competitive bodybuilders include human growth hormone (HGH), which can cause acromegaly.
Rest
Although muscle stimulation occurs in the gym lifting weights, muscle growth occurs afterward during rest. Without adequate rest and sleep, muscles do not have an opportunity to recover and build. About eight hours of sleep a night is desirable for the bodybuilder to be refreshed, although this varies from person to person. Additionally, many athletes find a daytime nap further increases their body's ability to build muscle. Some bodybuilders take several naps per day, during peak anabolic phases and during catabolic phases.