雖然對於職業及大學運動選手，肌酸是禁止使用的；但在八月份兒科期刊的一份報告顯示：在中年級和高年級運動選手中，仍使用相當多的肌酸補充品。肌酸是屬於合法的營養補充品，而也有些資料顯示，它能增進一些需要短暫爆發力的運動表現，如：摔角或美式足球。然而，該報告的主筆人，Jordan D. Metzl, MD表示：美國運動醫學院已表態，禁止十八歲以下運動員服用肌酸。
Creatine Abuse Widespread Among School Athletes
Experts Advise Against Use in Those Under 18
By Aman Shah, MD
WebMD Medical News
Reviewed by Michael W. Smith, MD
Aug. 7, 2001 -- Although creatine has been banned from many professional and collegiate sports, a report in the August issue of Pediatrics shows that the supplement's use abounds among middle and high school athletes.
Creatine is a legal nutritional supplement, and there is some data to indicate that it can enhance athletic performance, especially in athletic competitions that require short bursts of energy like wrestling or football. However, lead author Jordan D. Metzl, MD, says that the American College of Sports Medicine has taken the position that creatine should not be used by those age 18 or younger.
"There just haven't been enough studies to determine if there are risks from long-term use," says Metzl, medical director of the sports medicine institute for young athletes at the Hospital for Special Surgery, Cornell Medical Center in New York.
Among 1,103 school athletes in grades 6-12 who responded to a survey, 5.6% admitted using creatine. Overall, nearly 9% of boys and about 2% of girls admitted to creatine use. Use of the supplement increased markedly as the students neared high school graduation: 44% of the 12th grade athletes said they used creatine.
Almost three-quarters of the students used it to enhance performance, and 61.3% thought that it made them look good. But nearly half of the athletes who did not use it cited safety as the reason.
This performance-enhancing approach troubles Metzl, who calls it "a mind-set that is a slippery slope, meaning that athletes need to take something to enhance performance." Metzl says that creatine could be a gateway to other banned substances such as anabolic steroids or growth hormones.
John Acquaviva, PhD, assistant professor of physical education at Roanoke College in Salem, Va., says he thinks high school athletes nationwide are aware of creatine. He says, "When I teach a class to phys. ed. majors here, I always ask them how many of you know someone who has used creatine or use it yourself. Virtually every hand goes up, so the knowledge is out there."
Acquaviva, who was not involved in the study, doesn't recommend creatine for adolescents but says that it is "nonetheless difficult to deny the positive effects. I have seen about 20 studies that demonstrate creatine can improve performance at least a little. It's hard to argue with that."
The use of creatine, says Metzl, "appears to vary from school to school, and usually the use occurs in packs, meaning a group of kids on a team start taking it, and then it spreads out from there."
Ken Locker, athletic trainer at the Baylor Sports Care Program in Dallas, agrees with this assessment, adding that creatine use also varies from region to region.
Locker cites the case of a seemingly healthy, 18-year-old star football player whose blood pressure monitor read 160/110. Locker tells WebMD that after repeated questions, the football player finally admitted to creatine loading. "He had taken 24 g the night before. The body only produces 2 g of creatine, so he was really loading," says Locker.
Locker says that creatine does cause athletes to "bulk up," but that extra weight is actually caused by water retention, water that is pulled from cells, which can leave muscles with too little water. The result, says Locker, is increased risk for muscle strains.
Locker says he doesn't think that any creatine-driven improvements in performance can be sustained, and the extra bulk disappears once creatine use is stopped.