Muscle growth is more difficult to achieve in older adults than younger adults because of biological aging, which leads to many metabolic changes detrimental to muscle growth; for instance, by diminishing growth hormone and testosterone levels. Some recent clinical studies have shown that low-dose HGH treatment for adults with HGH deficiency changes the body composition by increasing muscle mass, decreasing fat mass, increasing bone density and muscle strength, improves cardiovascular parameters, and affects the quality of life without significant side effects.[46][47][unreliable medical source?][48]


Intensive weight training causes micro-tears to the muscles being trained; this is generally known as microtrauma. These micro-tears in the muscle contribute to the soreness felt after exercise, called delayed onset muscle soreness (DOMS). It is the repair of these micro-traumas that results in muscle growth. Normally, this soreness becomes most apparent a day or two after a workout. However, as muscles become adapted to the exercises, soreness tends to decrease.[22]
Bodybuilding became more popular in the 1950s and 1960s with the emergence of strength and gymnastics champions, and the simultaneous popularization of bodybuilding magazines, training principles, nutrition for bulking up and cutting down, the use of protein and other food supplements, and the opportunity to enter physique contests. The number of bodybuilding organizations grew, and most notably the International Federation of Bodybuilders (IFBB) was founded in 1946 by Canadian brothers Joe and Ben Weider. Other bodybuilding organizations included the Amateur Athletic Union (AAU), National Amateur Bodybuilding Association (NABBA), and the World Bodybuilding Guild (WBBG). Consequently, the male-dominated contests grew both in number and in size. Besides the many "Mr. XXX" (insert town, city, state, or region) championships, the most prestigious titles[according to whom?] were Mr. America, Mr. World, Mr. Universe, Mr. Galaxy, and ultimately Mr. Olympia, which was started in 1965 by the IFBB and is now considered the most important bodybuilding competition in the world.
The bulking and cutting strategy is effective because there is a well-established link between muscle hypertrophy and being in a state of positive energy balance.[19] A sustained period of caloric surplus will allow the athlete to gain more fat-free mass than they could otherwise gain under eucaloric conditions. Some gain in fat mass is expected, which athletes seek to oxidize in a cutting period while maintaining as much lean mass as possible.

This period also saw the rise of anabolic steroids in bodybuilding and many other sports. In bodybuilding lore, this is partly attributed to the rise of "mass monsters", beginning with Arnold Schwarzenegger, Sergio Oliva, and Lou Ferrigno in the late 1960s and early 1970s, and continuing through the 1980s with Lee Haney, the 1990s with Dorian Yates, Ronnie Coleman, and Markus Rühl, and up to the present day. Bodybuilders such as Greg Kovacs attained mass and size never seen previously but were not successful at the pro level. Others were renowned for their spectacular development of a particular body part, like Tom Platz or Paul Demayo for their leg muscles. At the time of shooting Pumping Iron, Schwarzenegger (while never admitting to steroid use until long after his retirement) said that "you have to do anything you can to get the advantage in competition".[citation needed] He would later say that he does not regret using anything.[8]
Bodybuilding became more popular in the 1950s and 1960s with the emergence of strength and gymnastics champions, and the simultaneous popularization of bodybuilding magazines, training principles, nutrition for bulking up and cutting down, the use of protein and other food supplements, and the opportunity to enter physique contests. The number of bodybuilding organizations grew, and most notably the International Federation of Bodybuilders (IFBB) was founded in 1946 by Canadian brothers Joe and Ben Weider. Other bodybuilding organizations included the Amateur Athletic Union (AAU), National Amateur Bodybuilding Association (NABBA), and the World Bodybuilding Guild (WBBG). Consequently, the male-dominated contests grew both in number and in size. Besides the many "Mr. XXX" (insert town, city, state, or region) championships, the most prestigious titles[according to whom?] were Mr. America, Mr. World, Mr. Universe, Mr. Galaxy, and ultimately Mr. Olympia, which was started in 1965 by the IFBB and is now considered the most important bodybuilding competition in the world.
Contrary to certain rumors that animal-based protein is more suitable to trigger muscle growth than plant-based protein, a study by Mangano et al. (2017) could not provide any evidence for this. In contrast, if combined properly, plant-based protein can even have a higher biological quality. A combination of one part wheat protein (e.g. seitan) and two parts soy protein (e.g. tofu) has thus been favored by many bodybuilders. Some bodybuilders, such as Patrik Baboumian and Robert Cheeke, follow a strict vegan diet.[37]
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.
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