^ Burd, Nicholas A.; Yang, Yifan; Moore, Daniel R.; Tang, Jason E.; Tarnopolsky, Mark A.; Phillips, Stuart M. (2012). "Greater stimulation of myofibrillar protein synthesis with ingestion of whey protein isolate v. Micellar casein at rest and after resistance exercise in elderly men". British Journal of Nutrition. 108 (6): 958–62. doi:10.1017/S0007114511006271. PMID 22289570.
Overtraining occurs when a bodybuilder has trained to the point where his workload exceeds his recovery capacity. There are many reasons why overtraining occurs, including lack of adequate nutrition, lack of recovery time between workouts, insufficient sleep, and training at a high intensity for too long (a lack of splitting apart workouts). Training at a high intensity too frequently also stimulates the central nervous system (CNS) and can result in a hyperadrenergic state that interferes with sleep patterns. To avoid overtraining, intense frequent training must be met with at least an equal amount of purposeful recovery. Timely provision of carbohydrates, proteins, and various micronutrients such as vitamins, minerals, phytochemicals, even nutritional supplements are acutely critical. A mental disorder, informally called “bigorexia” (by analogy with anorexia), may account for overtraining in some individuals. Sufferers feel as if they are never big enough or muscular enough, which forces them to overtrain in order to try and reach their goal physique.
Some bodybuilders use drugs such as anabolic steroids and precursor substances such as prohormones to increase muscle hypertrophy. Anabolic steroids cause hypertrophy of both types (I and II) of muscle fibers, likely caused by an increased synthesis of muscle proteins. They also provoke undesired side effects including hepatotoxicity, gynecomastia, acne, the early onset of male pattern baldness and a decline in the body's own testosterone production, which can cause testicular atrophy. Other performance-enhancing substances used by competitive bodybuilders include human growth hormone (HGH), which can cause acromegaly.
During the 1950s, the most successful and most famous competing bodybuilders[according to whom?] were Bill Pearl, Reg Park, Leroy Colbert, and Clarence Ross. Certain bodybuilders rose to fame thanks to the relatively new medium of television, as well as cinema. The most notable[according to whom?] were Jack LaLanne, Steve Reeves, Reg Park, and Mickey Hargitay. While there were well-known gyms throughout the country during the 1950s (such as Vince's Gym in North Hollywood, California and Vic Tanny's chain gyms), there were still segments of the United States that had no "hardcore" bodybuilding gyms until the advent of Gold's Gym in the mid-1960s. Finally, the famed Muscle Beach in Santa Monica continued its popularity as the place to be for witnessing acrobatic acts, feats of strength, and the like. The movement grew more in the 1960s with increased TV and movie exposure, as bodybuilders were typecast in popular shows and movies.
The winner of the annual IFBB Mr. Olympia contest is generally recognized as the world's top male professional bodybuilder. Since 1950, the NABBA Universe Championships have been considered the top amateur bodybuilding contests, with notable winners such as Reg Park, Lee Priest, Steve Reeves, and Arnold Schwarzenegger. Winners generally go on to become professional athletes.