A survey was used to collect anonymous cross-sectional data on demographics, exercise habits, and use of creatine and other supplements by exercisers in civilian (C) and military (M) health clubs. M (n = 133) reported more aerobic training and less use of creatine and protein supplements than C(n = 96, p < .05). Supplement users (SU, n = 194) and nonusers (SNU, n = 35) engaged in similar frequency and duration of aerobic exercise, as well as number of resistance exercise repetitions, but SU completed more sets for each resistance exercise (x̄ ± SE, 5 ± 1) than SNU (3 ± 1, p ≤ .05). Significant (p ≤ .05) associations were observed between SU and resistance training goal of strength (as opposed to endurance), as well as greater frequency of resistance training. Male gender, resistance training goal of strength, lower frequency and duration of aerobic training, and use of protein, ß-hydroxy-ß-methyl butyrate, and androstenedi-one/dehydroepiandrosterone supplements were all associated with creatine use (p < .05). For creatine users, the dose and length of creatine supplementation was 12.2±2.7g•day·1 for 40 ± 5 weeks. Popular magazines were the primary source of information on creatine (69%) compared to physicians (14%) or dietitians (10%, p ≤ .0001). This study underscores two potential public health concerns: (a) reliance on popular media rather than allied-health professionals for information on creatine, and (b) use of creatine, a popular supplement with unknown long-term effects, in combination with other anabolic supplements of questionable efficacy and/or safety.
Heather L. Sheppard, Sneha M. Raichada, Kellie M. Kouri, Lena Stenson-Bar-Maor, and J. David Branch
Michael H. Stone, Kimberly Sanborn, Lucille L. Smith, Harold S. O'Bryant, Tommy Hoke, Alan C. Utter, Robert L. Johnson, Rhonda Boros, Joseph Hruby, Kyle C. Pierce, Margaret E. Stone, and Brindley Garner
The purpose of this investigation was to study the efficacy of two dietary supplements on measures of body mass, body composition, and performance in 42 American football players. Group CM (n = 9) received creatine monohy-drate, Group P (n = 11) received calcium pyruvate. Group COM (n = 11) received a combination of calcium pyruvate (60%) and creatine (40%), and Group PL received a placebo. Tests were performed before (Tl) and after (T2) the 5-week supplementation period, during which the subjects continued their normal training schedules. Compared to P and PL. CM and COM showed significantly greater increases for body mass, lean body mass, 1 repetition maximum (RM) bench press, combined 1 RM squat and bench press, and static vertical jump (SVJ) power output. Peak rate of force development for SVJ was significantly greater for CM compared to P and PL. Creatine and the combination supplement enhanced training adaptations associated with body mass/composition, maximum strength, and SVJ; however, pyruvate supplementation alone was ineffective.
The effect of oral creatine supplementation on aerobic and anaerobic performance was investigated in 16 elite male rowers during 7-day endurance training. Before and after the daily ingestion of 20 g creatine monohydrate for 5 days (Cr-Group, n = 8) or placebo (Pl-Group, n = 8), subjects performed two exercise tests on a rowing ergometer: (a) incremental exercise consisting of 3-min stage durations and increased by 50 W until volitional exhaustion; (b) an all-out anaerobic exercise performed against a constant load of 7 W/kg. Heart rate and blood lactate concentrations were determined during exercise and recovery. Maximal power output did not significantly differ after the treatment in either group. The mean individual lactate threshold rose significantly after Cr treatment from 314.3 ± 5.0 W to 335.6 ± 7.1 W (p < .01), as compared with 305.0 ± 6.9 W and 308.9 ± 5.9 W (ns), before and after placebo ingestion, respectively. During the anaerobic test, the athletes supplemented with creatine were able to continue rowing longer (mean increase, 12.1 ± 4.5 s; p < .01) than Pl-Group (2.4 ± 8.2 s; ns). No significant differences were found between groups in blood LA after the all-out exercise. The results indicate that in elite rowers, creatine supplementation improves endurance (expressed by the individual lactate threshold) and anaerobic performance, independent of the effect of intensive endurance training.
David L. Mayhew, Jerry L. Mayhew, and John S. Ware
The purpose of this study was to determine the effect of long-term Cr supplementation on blood parameters reflecting liver and kidney function. Twenty-three members of an NCAA Division II American football team (ages = 19–24 years) with at least 2 years of strength training experience were divided into a Cr monohydrate group (CrM, n = 10) in which they voluntarily and spontaneously ingested creatine, and a control group (n = 13) in which they took no supplements. Individuals in the CrM group averaged regular daily consumption of 5 to 20 g (mean ± SD = 13.9 ± 5.8 g) for 0.25 to 5.6 years (2.9 ± 1.8 years). Venous blood analysis for serum albumin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, bilirubin, urea, and creatinine produced no significant differences between groups. Creatinine clearance was estimated from serum creatinine and was not significantly different between groups. Within the CrM group, correlations between all blood parameters and either daily dosage or duration of supplementation were nonsignificant. Therefore, it appears that oral supplementation with CrM has no long-term detrimental effects on kidney or liver functions in highly trained college athletes in the absence of other nutritional supplements.
Liam P. Kilduff, Yannis P. Pitsiladis, Louise Tasker, Jeff Attwood, Paul Hyslop, Andrew Dailly, Ian Dickson, and Stan Grant
This study examined the effects of Cr supplementation on muscle strength in conjunction with resistance training in nonresistance-trained males utilizing strategies previously reported in the literature to help optimize muscle Cr uptake. Nineteen nonresistance-trained males underwent 4 weeks of resistance training (3 days · week−1) while assigned to Cr (20 g · d−1 Cr + 140 g · d−1 glucose) for 7 days (loading), followed by 5 g · d−1 Cr + 35 g · d−1 glucose for 21 days (maintenance; n = 9) or placebo (160 g · d−1 glucose [loading] followed by 40 g · d−1 [maintenance; n = 10]). In subjects classified as “responders” to Cr on the basis of body mass changes (n = 7), the magnitude of change in 180∞ · s−1 isokinetic (p = .029) and isometric (p = .036) force was greater compared to the placebo group. A positive correlation was found between changes in body mass and 180º · s−1 isokinetic (loading: r = 0.68, p = .04; maintenance: r = 0.70, p = .037) and isometric (loading: r = 0.82, p < .01) force. Estimated Cr uptake was also positively correlated with changes in 60º · s−1 (r = 0.90, p < .01) and 180º · s−1 (r = 0.68, p = .043) isokinetic force, and isometric force (r = 0.71, p = .033). These results indicate that Cr supplementation can increase muscle strength (allied with 4 weeks of strength training) but only in subjects whose estimated Cr uptake and body mass are significantly increased; the greater the Cr uptake and associated body mass changes, the greater the performance gains.
Eric S. Rawson, Mary P. Miles, and D. Enette Larson-Meyer
Several dietary supplements, including carbohydrate, caffeine, creatine monohydrate, nitrate, beta-alanine, and sodium bicarbonate, are well-established performance enhancers (see Peeling et al., 2018 ). Additionally, the beneficial effects of protein on the adaptive response to exercise has been
Ronald J. Maughan
Creatine phosphate allows high rates of adenosine triphosphate resynthesis to occur in muscle and therefore plays a vital role in the performance of high-intensity exercise. Recent studies have shown that feeding large amounts of creatine (typically 20 g per day for 5 days) increases muscle total creatine (and phosphocreatine) content. The extent of the increase that is normally observed is inversely related to the presupplementation level. Vegetarians, who have a very low dietary creatine intake, generally show the largest increases. Creatine supplementation has been shown to increase performance in situations where the availability of creatine phosphate is important; thus, performance is improved in very high-intensity exercise and especially where repeated sprints are performed with short recovery periods. Creatine supplementation is widely practiced by athletes in many sports and does not contravene current doping regulations. There are no reports of harmful side effects at the recommended dosage.
Angela de Silva, Yasas Samarasinghe, Dhammika Senanayake, and Pulani Lanerolle
Intake of dietary supplements is widespread among athletes in developed countries. This study evaluated the use of dietary supplements in athletes from a developing country. Dietary supplementation practices of 113 national-level athletes age 15–35 yr in Sri Lanka were assessed. All athletes from track-and-field, badminton, football, swimming, cycling, and karate squads who consented to participate in the study were administered an anonymous questionnaire by an interviewer. Information on number of supplements taken, frequency of use, nature of product, rationale, sources of advice, and reasons for taking supplements was obtained. Most athletes (94%) consumed dietary supplements. On average, 3.7 products/day were consumed. Footballers had significantly lower intake of supplements than other athletes (footballers 71%, others 98%; p < .05). They also consumed fewer products per day (footballers 0.7, others 3.5; p < .05). Popular supplements included multivitamins, vitamin E, calcium, energy foods and drinks, and creatine. Multiple supplement use was common, with 29% athletes taking 4 products/day. The athletes sought advice on supplement use from sports doctors (45%), team coaches (40%), or friends (15%). Most took supplements to improve performance (79%), and 19% claimed to take supplements to improve their overall health status. Dietary supplement use is widespread among national-level Sri Lankan athletes. The ad hoc use of supplements indicates that educational intervention in the sporting community is essential.
Marc Francaux and Jacques R. Poortmans
Allegations about side effects of creatine supplementation by athletes have been published in the popular media and scientific publications.
To examine the experimental evidence relating to the physiological effects of creatine supplementation.
One of the purported effects of oral creatine supplementation is increased muscle mass. A review of the literature reveals a 1.0% to 2.3% increase in body mass, which is attributed to fat-free mass and, more specifically, to skeletal-muscle mass. Although it is unlikely that water retention can completely explain these changes, increase in muscle-protein synthesis has never been observed after creatine supplementation. Indirect evidence based on mRNA analyses suggests that transcription of certain genes is enhanced. Although the effect of creatine on muscle-protein synthesis seems irrefutable according to advertising, this allegation remains under debate in the scientific literature. The kidneys appear to maintain their functionality in healthy subjects who supplement with creatine, even over several months.
The authors, however, think that creatine supplementation should not be used by an individual with preexisting renal disease and that risk should be evaluated before and during any supplementation period. Even if there is a slight increase in mutagenic agents (methylamine and formaldehyde) in urine after a heavy load of creatine (20 g/day), their excretion remains within a normal range. No data are currently available regarding the potential production of heterocyclic amines with creatine supplementation. In summary, the major risk for health is probably associated with the purity of commercially available creatine.
Bethany Northeast and Tom Clifford
-generating capacity, delayed onset muscle soreness, efflux of myocellular proteins (e.g., creatine kinase [CK]), swelling of the affected limb, and restricted range of motion (ROM) ( Ebbeling & Clarkson, 1989 ; Hyldahl & Hubal, 2014 ; Mackey & Kjaer, 2017 ; Owens et al., 2018 ). These symptoms, especially the