Creatine Supplementation in Wisconsin High School Athletes

Transcription

1 Creatine Supplementation in Wisconsin High School Athletes Timothy A. McGuine, MS, ATC; Jude C. Sullivan, MS; David A. Bernhardt, MD ABSTRACT Background: Creatine is a nutritional supplement used to enhance athletic performance in collegiate and professional athletes. There is increasing evidence that high school athletes are using creatine as well. The objective of this study was to describe patterns of creatine supplementation as well as the behaviors and beliefs associated with creatine use in high school athletes. Methods: 4011 high school student-athletes from 37 public high schools in Wisconsin took part in a cross-sectional, multi-site, anonymous, descriptive survey. Measurements included self-reported patterns of creatine use. Results: 16.7% of the athletes (25.3% males, 3.9% females) reported using creatine. Creatine use was lowest in the 9th grade (8.4%) and highest in the 12th grade (24.6%). The percentage of participants in each sport who used creatine varied considerably from 1.3% (female cross country) to 30.1% (football). Increased strength was the most likely perceived benefit of creatine supplementation, while dehydration was cited most often as a perceived risk of creatine use. Users were encouraged to take creatine most often by their friends while their parents discouraged its use. Conclusion: Despite the lack of research regarding the efficacy or safety of creatine supplementation in high school athletes, creatine was used by 25% of males and 4% of female high school athletes in Wisconsin. High school athletes who use creatine may not be aware of the risks and benefits associated with creatine supplementation. Primary care providers and sports medicine professionals need to educate athletes, coaches and parents about the creatine use as a performance enhancing supplement. Mr. McGuine and Mr. Sullivan are from the University of Wisconsin Hospital Sports Medicine Center. Mr. Bernhardt is from the Department of Pediatrics, University of Wisconsin Hospital and Clinics. INTRODUCTION Use of nutritional supplements as ergogenic aids has gained widespread popularity in athletes in the United States. In recent years, creatine monohydrate, commonly called creatine, has been marketed as a legal, safe ergogenic aid. Recent media reports indicate creatine supplementation is widespread among collegiate, olympic and professional athletes. There is increasing anecdotal evidence that younger athletes, especially at the high school level, are emulating their older, elite counterparts by using creatine as well. In the United States, consumption of creatine in 1999 alone was estimated to exceed 2.5 million kilograms. 2 While creatine has been studied extensively, debate exists regarding both its efficacy and safety especially when it concerns the adolescent population. The American College of Sports Medicine published a round table report regarding creatine and its use based on the currently available literature. 2 The medical community is concerned regarding the potential for high school athletes to use supplements that are purported to have ergogenic qualities but have not been proven safe. Previous researchers have studied the prevalence of nutritional supplementation in high school athletes. 3,4,5,6,7 However, these studies were performed before creatine was widely marketed as an ergogenic aid. Recently, Greenwood et al, 8 and Labotz and Smith 9 reported on creatine supplementation in collegiate athletes. Some of these athletes who use creatine supplements stated that they had been doing so continuously for the last 4 years, making it likely they used them while attending high school. 8 Although interest in creatine use is unparalleled, studies documenting prevalence of use among high school athletes are lacking. The National Federation of High Schools has issued a position statement adopted by the Wisconsin Interscholastic Athletic Association (WIAA) regarding performance enhancement. 10 It reads in part, In order to minimize health and safety risks to student athletes, 25

2 maintain ethical standards and reduce liability risks, school personnel and coaches should never supply, recommend or permit the use of any drug, medication or food supplement solely for performance-enhancing purposes. In addition, we know of at least 3 school districts with specific policies prohibiting creatine use. In these districts, creatine supplementation was treated the same as tobacco and alcohol use and could lead to suspension from the team and or competition. We determined that, despite these prohibitions, creatine supplementation is widespread in Wisconsin high school athletes. This evidence was gathered by talking to primary care physicians and licensed athletic trainers who reported that large numbers of athletes, parents and coaches were seeking information regarding the safety and effectiveness of creatine. The purpose of this study was to describe patterns of creatine supplementation in Wisconsin high school athletes. In addition, we wanted to determine the knowledge, behaviors and attitudes of athletes who used creatine. METHODS For this study, a high school athlete was defined as an individual who participated or planned to participate in a school and Wisconsin Interscholastic Athletic Association-sponsored interscholastic competition, during the school year. In Wisconsin, there are approximately 64,000 student athletes at 429 high schools that meet this definition. School enrollments vary greatly, ranging from 89 to A stratified random sample of 90 public high schools (30 small, 30 medium, 30 large) representing 20.9% (90/429) of all public schools in Wisconsin was drawn. The total number of athletes in the 90 schools was estimated to be 13,400. Schools were classified as being located in 1 of 5 geographic regions (southeast, central, west, north central, northeast) representing the whole state and stratified according to enrollment (small = < 250, medium = , large = > 750). Officials at each of the 90 schools were contacted by letter, with follow-up by phone or in person, asking for their participation. A 22-question, 2 page survey was developed for this study by the authors and the University of Wisconsin Research Laboratory. The survey consisted of demographic information such as gender, age, year in school and sports participation. To obtain information on sport participation, we asked each athlete to check all of the sports in which they participated or planned to participate within the current school year. In Wisconsin, each athlete can participate in as many as 3 to 4 sports per year. For instance, an athlete could participate in cross country in the fall, swimming in the winter, track in the spring, and baseball in the summer. Questions were asked regarding whether the athlete had used creatine, as well as how he or she used and purchased creatine. Additional questions were asked regarding the athlete s perceived benefits and risks associated with creatine use. Finally, athletes were asked a series of questions concerning who influenced them to use creatine supplements. A committee of sports medicine professionals, (1 physician, 2 certified athletic trainers, 1 registered dietitian, and 1 exercise physiologist) who work closely with high school athletes on a daily basis determined content validity. The survey was pilot tested on a sample of high school athletes (n = 16) to insure that the content was at the appropriate reading and comprehension level for this population. The survey was approved by the Health Sciences Human Subjects Committee at University of Wisconsin. Surveys were administered by the authors or by certified athletic trainers (ATCs) from the Wisconsin Athletic Trainers Association during the school year. The high school athletes were told that participation was voluntary, respondents would remain anonymous and that individual or school information would not be made available to their parents, coaches or school officials. Data Analysis All analyses were performed with SPSS version (SPSS Inc., Chicago IL). Descriptive statistics were obtained for all demographic information. To help insure the generalizability of the findings, the values were weighted by region and school size for cross tabulation and analysis. The multipliers to determine weighting were calculated by taking the percent of the sample population of each group (school size and region) and multiplying by the sample size of 37. This number was then divided by the total number of schools in each group to come up with the weighing factor. RESULTS Of the 90 schools contacted, 37 (41.1%) agreed to allow their athletes to be surveyed. This represents 8.6% (37/429) of the total number of public high schools in the state. A total of 4011 high school athletes (age = 16.1 ± 1.2 yrs.) completed the survey. The response rate (determined by dividing the number of athletes who completed the survey by the total number of athletes in the 37 schools) was 72.7% (4011/5513). As a result of weighting, it was determined that the weighted sample of 4087 responses 26

3 would be used in all analyses. The sample demographics are found in Table 1. A total of 685 (16.8%) of the athletes (age = 15.9 ± 1.1 yrs.) reported having used creatine. The percentage of athletes using creatine was 20.6% for small schools, 16.4% for medium schools and 15.4% for large schools (Chi=10.10, df=2, p<0.05). Creatine was used more by males than females (25.3% vs 3.9%; Chi= df=1 p<0.05). Creatine use was lowest in 9th graders (8.4%) and highest for 12th graders (24.6%) (Chi=136.38, df=3, p=0.05). The distribution of creatine use by gen - der, grade and school size is found in Table 2. High school athletes frequently participate in more than one sport each year. To determine the prevalence of creatine supplementation by sport participation, we asked the athletes to check each sport they play from a list of all possible sports. In our sample, the 4087 athletes translated to 7805 sports participants. The prevalence of creatine supplementation for each sport was determined by taking the number of participants who use creatine and dividing it by the total number of participants for that sport. In females, creatine supplementation was highest in track (5.4%) and lowest in cross country (1.3%). In males, football (30.1%) had the highest percentage of participants who used creatine while golf (15.8%) had the lowest percentage of participants who used creatine. In sports where both males and females compete (basketball, cross country, golf, soccer, swimming, tennis and track) males had a higher percentage of participants who use creatine. There was considerable variation in the percentage of participants in each sport who used creatine (Table 2). We acknowledge that the number of creatine users for each sport could be inflated since athletes were allowed to indicate all sports in which they participated. Therefore, readers should view the results for individual sport participants with caution. Creatine users were asked what benefits and or risks were associated with creatine supplementation (Table 3). We asked the athletes to check all responses (perceived benefit) they were aware of. Six hundred eighty-one (99.2%) creatine users provided information on the perceived benefits of creatine. Increasing strength (70.7%) and power (64.2%) were listed as the two top benefits. Six hundred thirty-five (92.5%) creatine users answered questions concerning the risks of creatine supplementation. Again, the athletes checked any response (possible harmful or unwanted side effect) they knew about. Dehydration (38.6%) and none (36.2%) were the top two responses. Fifty- Table 1. Description and Distribution of the Sample Athletes Used Characteristics Surveyed Creatine (%) Gender * Female (3.9) Male (25.3) Year in School (8.4) (12.6) (23.1) (24.6) School Size (n) Small (13) (20.6) Medium (11) (16.4) Large (13) (15.4) Region of WI SE (20.7) SW (15.1) W (16.8) NC (17.6) NE (21.0) * Chi= , 1 df, p=0.000 Chi= , 3 df, p=0.000 Chi=10.101, 2 df, p=0.006 Chi=18.653, 4 df, p=0.001 Table 2. Prevalence of creatine use in Wisconsin high school sport participants Female Male Sport Creatine % Creatine % Users Users Participants Participants Baseball 192/ Basketball 20/ / Cross Country 2/ / Football 418/ Golf 1/ / Gymnastics 2/ Hockey 35/ Soccer 4/ / Softball 17/ Swimming 3/ / Tennis 3/ / Track 27/ / Volleyball 25/ Wrestling 0/ / one respondents (7.2%) who checked other provided responses that included acne, heart problems, diarrhea, mood swings and sexual dysfunction. Additionally, 9.6% of creatine users stated that they experienced side effects and listed cramping and dehydration most often, followed by stomach upset. 27

4 Table 3. Perceived benefits and risks of creatine supplementation in high school athletes who have used creatine (check all that apply) Perceived Benefits (n = 685) N (%) Increased strength 481 (70.2) Increased power 437 (63.6) Weight gain 385 (56.2) Better endurance 282 (41.1) Increased speed 242 (35.3) Decreased body fat 162 (23.6) Other 50 (7.2) None 14 (0.2) Perceived Risks (n = 635) Dehydration 246 (38.6) None 230 (36.2) Muscle cramps 212 (33.3) Upset stomach 124 (19.6) Muscle strain 99 (15.5) Kidney damage 78 (12.2) Liver damage 75 (11.8) Other 35 (5.6) Table 4. Encouragement/discouragement for supplementation in high school athletes that have used creatine (check all that apply) Who encouraged you to use creatine (n = 415) N (%) Friends 303 (73.1) Coaches 108 (25.9.) Other 99 (23.8) Parents 76 (18.4) Physician 36 (8.8) Teacher 30 (7.2) Who discouraged you from using creatine? (n =296) Parents 170 (57.5) Coaches 107 (36.1) Friends 96 (32.3) Teachers 51 (17.4) Physician 41 (13.9) Other 14 (4.9) Five hundred fifty-one (89.6%) have used creatine as part of a regular conditioning program; 457 (66.6%) stated that they use creatine during their sport season; and 536 (78.1%) reported using creatine during the off-season. Sources for encouragement or discouragement for creatine supplementation are found in Table 4. Four hundred fifteen (60.4%) creatine users indicated that they had received encouragement to use creatine, while 297 (45.6%) were discouraged from using creatine. Friends were the most likely source of encouragement for creatine use while parents were most often cited as discouraging creatine use. At the time of the survey, 337 (49.2%) creatine users stated that they were currently using creatine. Of these creatine users, 200 (59.3%) stated that their parents were aware of their creatine use while only 125 (37%) stated that their coaches knew they were using creatine. The purchasing and use patterns associated with creatine supplementation are found in Table 5. One hundred twenty-four (38%) reported using creatine daily, while 122 (37.4%) used it 1 to 3 days per week. One hundred twenty-nine (38.2%) spent $30 to $60 per month on creatine supplementation products; 248 (78.4%) athletes cited health /nutrition stores as the source of their creatine products. DISCUSSION To our knowledge, this study is the first to report the prevalence of creatine supplementation in a large sample of high school athletes. Although only 41% of schools contacted allowed athletes to participate in the study, the use of ATCs in the schools to implement the survey and the fact that the responses were anonymous helped generate a 70% response rate. Despite the lack of proven scientific data defining a positive ergogenic effect in high school athletes, this study demonstrates that almost 17% have used creatine. Our findings that creatine use was higher in males than females, increased with age, and was highest in sports such as football and hockey is in agreement with previous researchers. Sobal and Marquardt 6 surveyed 742 athletes in 1 county and found that boys were more likely to feel that using supplements enhanced muscle development and sports performance. Krowchuk 4 reported that 33.4% of 295 high school athletes reported using protein powders. In addition, males were most likely to believe that supplements could positively affect their performance. Massad et al 5 surveyed high school athletes in Indiana. They reported that football and hockey players were more likely to use supplements than participants in other sports. Smith and Dahm studied 5 Minnesota high schools and reported that 8.2% of all athletes and 21% of football players used creatine. 11 When comparing our findings with similar studies of collegiate athletes we found similarities and differ- 28

5 Table 5. Purchase/spending habits for high school athletes currently taking creatine N (%) How much do you spend monthly on creatine products? (n = 306) < $ (34.0) $ $ (41.8) $ $ (13.1) > $ (11.1) How often do you use creatine? (n = 326) Daily 124 (38.0) 4 6 days per week 80 (24.5) 1 3 days per week 122 (37.4) Where do you purchase creatine products? (n = 317) Health / Nutrition stores 248 (78.4) Friends 42 (13.2) Other 36 (11.3) Internet 33 (10.5) Mail order 29 (9.1) Coaches 21 (6.6) Other 35 (5.6) ences regarding creatine supplementation. Specifically, the percentage of high school athletes who used creatine was lower than rates reported by Greenwood et al (41%) 8 and Labotz and Smith (28%). 9 However, the prevalence of creatine use by gender was similar to our findings. In both of these studies, creatine supplementation was much higher in males than females. These results are similar to our own findings, especially when comparing sports with dual participation such as track, basketball, soccer and swimming. Although creatine users in our study believe that increasing strength and power are the top two benefits of creatine supplementation, we could find no studies documenting benefits in high school athletes. In fact, most studies looking at performance enhancement used males age as subjects, with varied athletic abilities and training regimens. 2 A critical review of creatine supplementation and performance looked at all studies between 1990 and 1998 that were done in a double-blind placebo-controlled fashion with a minimum of 6 participants. 13 Studies that have demonstrated an ergogenic effect of creatine involve repeated maximal bouts of stationary cycling and weight lifting repetitions although there are other similar studies which show no effect. 13 In addition, creatine has been shown to increase weight gain both in short- and long-term supplementation. 14 Risk of dehydration was identified by 39% of the creatine users in our study as a possible unwanted side effect. Most of what is known in terms of side effects of creatine supplementation is anecdotal. 2,13 No studies have conclusively demonstrated any of these theoretical side effects, and long-term side effects are unknown. Interestingly, 36% of the respondents did not perceive any risk with using this supplement. It is our experience that young athletes often assume that a dietary supplement such as creatine must be safe if they can purchase it in a retail store. In our sample, 78% of the creatine users purchased their creatine at health/nutrition stores. Fifty-seven percent of creatine users stated that parents tried to discourage them from using creatine. This is higher than the 36% of users who stated that coaches tried to discourage the use of creatine. It is interesting to note that only 39% of the users stated that their coaches were aware of their creatine use and 65% said their parents were aware. This indicates that high school coaches and parents may underestimate the prevalence of supplementation in this population. We were surprised to find that the highest percentage of athletes who reported using creatine attended small schools. While we cannot fully explain this finding, we feel that this may be a reflection of peer influence in these smaller schools. Of 415 creatine users, 303 (73.1%) stated that their friends encouraged them to use creatine. In our experience working with these schools, we observe that athletes at small schools are more likely to come in contact and interact with athletes from other grades and sports than athletes at larger schools. This potential for increased interaction may lead to an increased awareness of creatine supplementation, which might influence other athletes to use it. The frequency of creatine supplementation varied significantly by sport participation. However, these figures should be interpreted with caution for several reasons. First, when answering our survey, athletes were allowed to indicate all of the sports they participate in (up to 4). Therefore, an athlete who reported using creatine would be counted as a percentage of the respondents for each sport they checked. Second, some sports, such as female golf, gymnastics, swimming, tennis and wrestling, as well as male swimming and tennis, had a low total number of participants (<85) who participated in the survey. The percentage of users may be skewed with relatively few participants. We are much more confident of the prevalence rates for such sports as basketball (n=1458), football (n=1388), and track (n=1115). 29

6 We recognize several limitations of this study. First, while anonymous self report surveys are convenient methods to gather data, they may be biased in regards to the structure and wording of survey questions. To limit possible bias, the survey was designed and critiqued by sports medicine and survey method professionals before it was implemented. The survey was pilot tested on a group of high school athletes. As a result, several questions were modified to enhance the reader clarity. For instance, instead of having athletes write answers to specific questions, we provided multiple responses that the athletes could simply mark to indicate their answers. Second, we recognize the limitations with regard to information on non-responders. While we know the enrollment and region of the schools that declined to take part in our study, we have no information on the athletes in these schools. Even after speaking to school officials in person, a large number had no desire to participate and we had to respect their wishes. We had a number of schools decline to participate because the school administrators we contacted were not aware that high school athletes would use any performance enhancing aids. On the other hand, we had several schools decline to participate since they had evidence that large numbers of athletes were using creatine supplied by their coaches. One administrator confided that due to the level of creatine use in his school, the school board held several contentious meetings to develop specific policies to stop this practice. He thought that participating in this survey would bring up an issue the school wanted to put behind it. In addition, to insure confidentiality of all students, we were not allowed to gather data on individual athletes who declined to participate in the study. To insure school cooperation, taking part in the survey was entirely voluntary. However, this method of seeking voluntary cooperation from students is used by researchers implementing the youth behavior risk survey as a valid method to obtain information regarding beliefs and behaviors in adolescent populations. 14,15 CONCLUSION Despite lack of scientific proof of ergogenic or detrimental side effects, almost 25% of male and 4% of female Wisconsin high school athletes have used creatine in hopes of aiding their performance. Health professionals and school officials may underestimate the scope of creatine supplementation in high school athletes. We encourage primary care physicians who treat young athletes to screen for performance enhancing supplements during regular physical examinations or when completing WIAA mandated sport physicals. Medical professionals need to work with educators to design and implement education programs that discuss the benefits and risks of creatine supplementation in young athletes, especially those most likely to use creatine. Since creatine use was reported in all high school grades, these education programs should begin as early as junior high school and should involve athletes, parents, coaches and school administrators. ACKNOWLEDGMENTS Funding for this study was provided by the Wisconsin Athletic Trainers Association and the Sports Medicine Classic Fund of the UW Health Sports Medicine Center. REFERENCES 1. Applegate EA, and Grivetti LE. Search for the competitive edge: a history of dietary fads and supplements. J Nutr. 1997;127:869S-873S. 2. Terjung R L, Clarkson P, Eichner ER, et al. The physiological and health effects of oral creatine supplementation. Med Sci Sports Exerc. 2000;32: Buckley WE, Yesalis CE, Friedl KE, Anderson WA, Streit AL. Estimated prevalence of anabolic steroid use among male high school seniors. JAMA. 1988;260: Krowchuk DP, Anglin TM, Goodfellow DB, Stancin T, Williams P, Zimet GD. High school athletes and the use of ergogenic aids. Am J Dis Child. 1989;143: Massad SJ, Sheir NW, Koceja DM, Ellis NT. High school athletes and nutritional supplements: A study of knowledge and use. Int J Sports Nutr. 1995;5: Sobal J, Marquardt LF. Vitamin/mineral supplement use among high school athletes. Adolescence. 1994;29: Windsor R, Dumitro D. Prevalence of anabolic steroid use by male and female adolescents. Med Sci Sports Exer. 1989;21: Greenwood M, Farris J, Kreider R, Greenwood L, Byars A. Creatine supplementation patterns and perceived effects in select division I collegiate athletes. Clin J Sport Med. 2000;10: LaBotz M, Smith BW. Creatine supplement use in an NCAA division I athletic program. Clin J Sport Med. 1999;9: WIAA Medical Policies and Procedures. Wisconsin Interscholastic Athletic Association, revised 6/01: Smith J, Dahm DL. Creatine use among a select population of high school athletes. Mayo Clin Proc. 2000;75: Juhn MS, Tarnopolsky M. Oral Creatine Supplementation and Athletic Performance: A Critical Review. Clin J Sport Med. 1998;8: Juhn MS, Tarnopolsky M. Potential Side Effects of Oral Creatine Supplementation: A Critical Review. Clin J Sport Med. 1998; 8: Kann L. The Youth Risk Behavior Surveillance System: measuring health-risk behaviors. Am J Health Behav. 2001;25(3): Crossett LS, Everett SA, Brener ND, Fishman JA, Pechacek TF. Measuring adherence to the CDC guidelines for school health programs to prevent tobacco use and addiction. J Health Ed. 1999;30(5):S4-S11. 30

7