Use of Oral Creatine as an Ergogenic Aid for Increased Sports Performance: Perceptions of Adolescent Athletes.

ABSTRACT

Background. Competitive athletes, including adolescents, seek ways to gain advantage over competitors. One ergogenic aid is creatine, a naturally occurring nitrogen compound found primarily in skeletal muscle. Increasing creatine levels may prolong skeletal muscle activity, anchancing work output.

Methods. A questionnaire assessing awareness and use of creatine supplementation was completed by 674 athletes from 11 high schools. Data were statistically analyzed to determine variation among groups.

Results. Of those surveyed, 75% had knowledge of creatine supplements, and 16% used creatine to enhance athletic performance. Percentage of use increased with age and grade level. Awareness and use were greater among boys than girls. Adverse effects were reported by 26%. Most athletes consumed creatine using a method inconsistent with scientific recommendations.

Conclusions. Use of creatine by adolescent athletes is significant and inconsistent with optimal dosing. Physicians, athletic trainers, and coaches should disseminate proper information and advise these adolescent athletes.

IN SKELETAL MUSCLE, creatine is primarily stored as free creatine and phosphocreatine (PCr) and is found naturally in foods such as meat and fish. Phosphocreatine is the first primary fuel reserve for the resynthesis of adenosine triphosphate during anaerobic exercise. [1,2] Therefore, rapid depletion of muscle PCr is believed to be a limiting factor during maximal anaerobic work. Increasing creatine levels may prolong skeletal muscle activity, thus enhancing work output.

Creatine supplementation can increase total creatine content in muscle by more than 20%. [3] The maximum level is achieved most quickly by consuming large daily doses (20 to 30 g) for 3 to 5 days, followed by a daily maintenance dose of 2 to 3 g. [4-7] The same creatine levels can be achieved more slowly by taking a 3 g maintenance dose for 28 days. [8]

The effectiveness of increased PCr stores in the body is debated. Creatine supplementation has been shown to improve exercise performance in repeated bouts of stationary cycling ranging from 5 to 60 seconds. [9-12] Specific increases have been documented in peak power, total work, and decreased lactate production. [5,13,14] While significant enhancements have been reported in high-intensity, short-duration exercise, it does not appear to be beneficial in endurance sports. [15-17]

No randomized trials have evaluated shortor long-term adverse effects of creatine, though there are anecdotal reports of dehydration, musculotendinous strains, renal dysfunction, rhabdomyolysis, gastrointestinal disturbances, and increased levels of creatine in the brain. [18-20]

Competitive athletes at all levels are searching for an advantage over their competitors.

Often, ergogenic aids are sought to gain that advantage. Ethical issues are raised by this behavior and are compounded further when the substances being used do not live up to claims or, more importantly, threaten the health of users. The adolescent population, because they are still developing physically and emotionally, have the most to lose. The purpose of our survey was to determine the use of oral creatine as an ergogenic aid among the adolescent athlete population.

MATERIALS AND METHODS

A survey instrument (Appendix) containing 18 questions on oral creatine supplementation was developed and distributed to 11 local public and private schools in southeast Tennessee and northwest Georgia over a 3-month period. All schools serviced by certified athletic trainers employed by our center and another local sports medicine facility were asked to participate. Administrators at each school were given copies of the survey questions and approved the study.

The procedure used to distribute and collect the questionnaires began by convening the athletic team in a meeting. The athletic trainer or coach distributed the questionnaires. The reason for the survey was explained, and the students were asked to complete the questionnaire to the best of their knowledge, with truthful, accurate responses. Anonymity of the participants was emphasized. The survey provided an "other" option, allowing the students to provide an answer not listed. The survey inquired about demographic information, knowledge and use of creatine and other ergogenic substances, manner of use, and effects from use. Measures taken to minimize the amount of false data included assuring the athletes that their answers would remain anonymous, explaining to them that participation was voluntary, and having the survey administrator leave the room while the forms were completed.

Categorical data, such as knowledge or use of creatine, were analyzed by comparing the two binomial proportions using [[chi].sup.2] analysis. Data trends, including effects of age, were studied using linear regression analysis to determine correlation between variables.

RESULTS

Of the 674 athletes surveyed, all complied. The survey population was 469 boys (70%) and 205 girls (30%). Ages of the athletes varied between 13 and 19 years (mean, 15.9 years). Five hundred four of the athletes (75%) were aware of oral creatine supplements, and 110 (16%) used them. Awareness (P[less than] .005) and use (P[less than] .001) were significantly higher among male athletes than female athletes. Of the 469 male athletes surveyed, 395 (84%) were aware of creatine, and 106 (23%) used creatine. Among the female athletes, 109 (53%) were aware of creatine, and 4 (2%) used the supplement. Participants were most likely to learn of oral creatine through a friend (43%), media (22%), or an athletic coach (19%) (Table 1).

The percentage of creatine use increased with age ([r.sub.s] = 0.947) and grade ([r.sub.s] = 0.959) (Table 2). The majority of athletes (65%) had taken creatine for less than 6 months. One hundred seven (97%) of the athletes taking creatine reported some benefit. Increased strength and increased muscle mass were the most common perceived benefits (Table 3).

Of the 110 athletes taking creatine, 29 (26%) indicated that they had side effects. Possible side effects from which participants could choose included those related to creatine through anecdotal reports (stomach cramps, diarrhea, nausea, muscle cramps, dizziness, and increased thirst) and other effects not commonly attributed to the supplement (headache, increased heart rate, and fatigue). The most commonly reported adverse effects were of the known side effect category and included muscle cramps (66%), increased thirst (52%), and stomach cramps (45%) (Table 3).

Athletes were asked about the manner in which they used creatine. Of the 110 adolescents using the supplement, 76 (69%) reported taking a "loading" dose. The most common pattern of loading was ingesting 5 to 10 g of creatine for either 3 or 5 days. Table 4 lists the patterns of loading used by study participants. Almost all of the athletes using creatine (109 of 110) took a maintenance dose. The largest percentage of users took 5 to 10 g/day (44%), and 38% took [less than]5 g/day (Table 4).

We hypothesized that creatine use might be an indicator of steroid use among athletes. Twelve students (11%) reported using steroids including androstenedione. Of these 12 students, 7 were using creatine. Since only 11% of creatine users reported taking steroids or androstenedione, it should not be assumed that they are using additional ergogenic aids.

DISCUSSION

Creatine has recently gained substantial popularity as a potential ergogenic aid to enhance athletic performance. With increasing demands on adolescent athletes to improve performance to be successful or to compete for college scholarships, it is possible that these athletes may take nutritional supplements to achieve their goals. Adolescent athletes are susceptible to the complexities surrounding the use of ergogenic aids to increase athletic performance because they are still in a process of physical and emotional growth. Before issues can be addressed, however, it must be determined whether a potential problem exists. Our survey determines the frequency of creatine use by teenage athletes to increase athletic performance.

Our survey revealed that three fourths of the adolescent athletes surveyed were aware of creatine supplements. This substantiates the potential for use of this ergogenic aid. Unfortunately, the product information is primarily spread through word of mouth, which may result in misinformation. Harris et al [3] reported that maximum loading of creatine occurred during the first 2 days and that a daily dose of 2 to 3 g was adequate to maintain the maximum level of creatine. More than 40% of survey participants used an incorrect loading method, and 70% took excessive amounts as a maintenance dose. Athletes who loaded 5 to 10 g of creatine per day for 3 to 5 days were underloading, based on the scientific literature.

Manufacturers' marketing claims and varying instructions for use compound the problem of misinformation. Generally, manufacturers' instructions for use directed the athletes to consume more than was necessary to obtain and maintain maximum creatine levels based on values in the scientific literature. Also, no creatine dosing standards exist for children or adolescents, and the American College of Sports Medicine supports that creatine supplementation is not advisable for the pediatric population under 18 years old.

The percentage of athletes surveyed who reported using creatine (16%) was much smaller than the percentage of those who were aware of the supplement. Use increased with age and grade level. This suggests that as the level of competition increases, so does the pressure to find ways to enhance performance. As an athlete progresses through school, competition for a starting position or for a scholarship opportunity increases. This places pressure on the athlete to perform at a higher level. Ergogenic aids offer an alternative for athletes with hopes of potentially enhancing their performance.

Our survey results indicate a need to address the use of creatine and other performance-enhancing supplements with school athletes. It is important that these athletes are provided with accurate information about the true benefits of ergogenic aids, as well as proper instructions on how to take the supplements and the associated risks. Physicians, athletic trainers, and coaches should use their working relationships with adolescent athletes to begin this important task.

References

(1.) Poortmans JR, Auquier H, Renaut v, et al: Effect of short-term creatine supplementation on renal responses in men. Eur J Appl Physiol 1997; 76:566-567

(2.) Lipskaya TY, Geiger PJ, Bessman SP: Compartmentation and metabolic parameters of mitochondrial hexokinase and creatine kinase depend on the rate of oxidative phosphorylation. Biochem Mol Med 1995; 55(2):81-89

(3.) Harris RC, Soderlund K, Hultman E: Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clin Sci 1992; 83:367-374

(4.) Cooke WH, Grandjean WP, Barnes WS: Effect of oral creatine supplementation on power output and fatigue during bicycle ergometry. J Appl Physiol 1995; 78:670-673

(5.) Greenhaff PL, Constantin-Teodosiu D, Casey A, et al: The effect of oral creatine supplementation on skeletal muscle ATP degradation during repeated bouts of maximal voluntary exercise in man. J Physiol 1994; 476:84

(6.) Maughan RJ: Creatine supplementation in exercise performance. Int J Sports Nutr 1995; 5:94-101

(7.) Mujika I, Padilla S: Creatine supplementation as an ergogenic aid for sports performance in highly trained athletes: a critical review. Int J Sports Med 1997; 18:491-496

(8.) Hultman E, Soderland K, Timmons JA, et al: Muscle creatine loading in men. J Appl Physiol 1996; 81:232-237

(9.) Clarkson PM: Nutrition for improved sports performance. Sports Med 1996; 6:393-401

(10.) Greenhaff PL, Casey A, Short AH, et al: Influence of oral creatine supplementation on muscle torque during repeated bouts of maximal voluntary exercise in man. (Yin Sci 1993; 84:565-571

(11.) Soderlund K, Balsom PD, Ekblom B: Creatine supplementation and high intensity exercise: influence on performance and muscle metabolism. Clin Sci 1994; 87(suppl):120-121

(12.) Thompson CH, Kemp GJ, Sanderson AL, et al: Effect of creatine on aerobic and anaerobic metabolism in skeletal muscle in swimmers. Br J Sports Med 1996; 30:222-225

(13.) Dawson B, Cutler M, Moody A, et al: Effects of oral creatine loading on single and repeated maximal short sprints. Aust J Sci Med Sport 1995; 27:56-61

(14.) Volek JS, Kraemer WJ, Bush JA, et al: Creatine supplementation enhances muscular performance during high intensity resistance exercise. J Am Diet Assoc 1997;97:765-770

(15.) Graham AS, Hatton RC: Creatine: a review of efficacy and safety. J Am Pharm Assoc (Wash) 1999; 39:803-810

(16.) Mujika I, Padilla S, Ibanez J, et al: Creatine supplementation and sprint performance in soccer players. Med Sci Sports Exerc 2000; 32:518-525

(17.) Terjung RL, Clarkson P, Eichner ER, et al: American College of Sports Medicine roundtable. the physiological and health effects of oral creatine supplementation. Med Sci Sports Exerc 2000; 32:706-717

(18.) Dechent P, Pouwels PJ, Wilken B, et al: Increase of total creatine in human brain after oral supplementation of creatine-monohydrate. Am J Physiol 1999; 277(3 Pt 2):R698-R704

(19.) Pritchard NR, Kalra PA: Renal dysfunction accompanying oral creatine supplements. Lancet 1998; 351:1252-1253

(20.) Robinson SJ: Acute quadriceps compartment syndrome and rhabdomyolysis in a weight lifter using high-dose creatine supplementation. J Am Board Fam Pract 2000; 13:134-137

TABLE 1. How Participants Learned of Creatine Monohydrate Use
                  Athletes
Knowledge Source      Male  Female  Percentage
Friend                 273      58        43.3
Media                  125      44        22.1
Coach                  132      12        18.8
Parents                 68       5         9.6
Athletic trainer        22       8         3.9
Other                    8       7         2.0
Teacher                  0       1         0.1
TABLE 2. Age and Grade Level of Participants Using Creatine
Monohydrate to Enhance Athletic Performance
           Total        No. (%)
         Population  Using Creatine
Age *
  13          7          0 (0)
  14        103          5 (5)
  15        147         18 (12)
  16        196         36 (18)
  17        158         34 (22)
  18         61         16 (26)
  19          2          1 (50)
Grade +
   8          9          0 (0)
   9        155          8 (5)
  10        167         29 (17)
  11        186         38 (20)
  12        157         35 (22)
(*) rB = 0.947.
(+) rB = 0.959.
TABLE 3. Benefits and Adverse Effects Claimed by 100 Athletes Using
Creatine
                                  Grade
                                    9    10  11  12  Total (%)
Benefits
  Increased strength                4    22  28  24   78 (71)
  Increased muscle mass             4    22  25  22   73 (66)
  Increased athletic performance    2    14  16  15   47 (43)
  Increased weight gain             4     9  10  17   40 (36)
  Increased endurance               4    11   9   6   30 (27)
  Other                             1     2   4   3    9 (8)
  No difference                     0     1   1   0    3 (3)
Adverse Effects
  Muscle cramps                     1     4   8   6   19 (17)
  Increased thirst                  1     6   3   5   15 (14)
  Stomach cramps                    0     5   5   3   13 (12)
  Diarrhea                          0     1   1   3    5 (5)
  Nausea                            0     2   0   1    3 (3)
  Headache *                        0     2   3   2    7 (6)
  Dizziness *                       0     2   1   3    6 (5)
  Fatigue *                         1     0   2   2    5 (5)
  Increased heart rate *            0     1   0   0    1 (1)
(*) Effects not typically associated with oral creatine
supplementation.
TABLE 4. Oral Creatine Loading and Maintenance Patterns by School Grade
                      Grade
                        9    10  11  12  Total (%)
Loading pattern
  5-10 g/3 days         2     7   6   6   21 (19)
  5-10 g/5 days         2     7   7   5   21 (19)
  15-20 g/3 days        2     1   4   4   11 (10)
  15-20 g/5 days        1     3   6   3   13 (12)
  25-30 g/3 days        0     1   1   4    6 (5)
  Other                 0     1   2   1    4 (4)
Maintenance pattern
  [less than]5 g/day    5    11  12  13   41 (37)
  5-10 g/day            2    11  20  15   48 (44)
  15-20 g/day           1     3   4   6   14 (13)
  Other                 0     4   2   0    6 (5)

KEY POINTS

* Creatine, a naturally occurring nitrogen compound found primarily in skeletal muscle, has become popular among competitive athletes as a potential ergogenic aid.

* Most adolescent athletes surveyed about their knowledge and use of creatine reported that they knew of such supplements, and a significant number used creatine to enhance athletic performance.

* Marketing claims and instructions for creatine use vary, and no creatine dosing standards exist for adolescents.

* Adolescent athletes need accurate information from their physicians and trainers about the true benefits of ergogenic aids, proper dosing instructions, and associated risks.