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Creatine supplementation and health variables: A retrospective study
Abstract
Purpose:
Long-term safety of creatine supplementation has been questioned. This retrospective study was performed to examine markers related to health, the incidence of reported side effects and the perceived training benefits in athletes supplementing with creatine monohydrate.
Methods:
Twenty-six athletes (18 M and 8 F, 24.7 +/- 9.2 y; 82.4 +/- 20.0 kg; 176.5 +/- 8.8 cm) from various sports were used as subjects. Blood was collected between 7:00 and 8:30 a.m. after a 12-h fast. Standard clinical examination was performed for CBC and 27 blood chemistries. Testosterone, cortisol, and growth hormone were analyzed using an ELISA. Subjects answered a questionnaire on dietary habits, creatine supplementation, medical history, training history, and perceived effects of supplementation. Body mass was measured using a medical scale, body composition was estimated using skinfolds, and resting heart rate and blood pressure were recorded. Subjects were grouped by supplementation length or no use: Gp1 (control) = no use (N = 7; 3 F, 4 M); Gp2 = 0.8-1.0 yr (N = 9; 2 F, 7 M); and Gp3 = 1(+) (N = 10; 3 F, 7 M).
Results:
Creatine supplementation ranged from 0.8--4 yr. Mean loading dose for Gp2 and Gp3 was 13.7 +/- 10.0 and the maintenance dose was 9.7 +/- 5.7 g.d(-)1. Group differences were analyzed using one-way ANOVA.
Conclusions:
Expected gender differences were observed. Of the comparisons made among supplementation groups, only two differences for creatinine and total protein (P < 0.05) were noted. All group means fell within normal clinical ranges. There were no differences in the reported incidence of muscle injury, cramps, or other side effects. These data suggest that long-term creatine supplementation does not result in adverse health effects.
... Both groups reported no changes in renal function. Schilling et al. [135] and Kreider et al. [136] reported no differences in resting serum LDH and CK, respectively, in elite strength/power athletes. Following a high-dose creatine loading protocol, athletes in these studies ingested maintenance doses of creatine 5-10 g/day for 0.8-4 years [135,136]. ...
... Schilling et al. [135] and Kreider et al. [136] reported no differences in resting serum LDH and CK, respectively, in elite strength/power athletes. Following a high-dose creatine loading protocol, athletes in these studies ingested maintenance doses of creatine 5-10 g/day for 0.8-4 years [135,136]. Collectively, these data indicate that creatine supplementation has no effect on bio-markers of muscle damage. The effects of creatine supplementation on markers of muscle damage at rest are summarized in Table 1 [133][134][135][136]. ...
... Collectively, these data indicate that creatine supplementation has no effect on bio-markers of muscle damage. The effects of creatine supplementation on markers of muscle damage at rest are summarized in Table 1 [133][134][135][136]. ...
Exertional (exercise-induced) rhabdomyolysis is a potentially life threatening condition that has been the subject of research, intense discussion, and media attention. The causes of rhabdomyolysis are numerous and can include direct muscle injury, unaccustomed exercise, ischemia, extreme temperatures, electrolyte abnormalities, endocrinologic conditions, genetic disorders, autoimmune disorders, infections, drugs, toxins, and venoms. The objective of this article is to review the literature on exertional rhabdomyolysis, identify precipitating factors, and examine the role of the dietary supplement creatine monohydrate. PubMed and SPORTDiscus databases were searched using the terms rhabdomyolysis, muscle damage, creatine, creatine supplementation, creatine monohydrate, and phosphocreatine. Additionally, the references of papers identified through this search were examined for relevant studies. A meta-analysis was not performed. Although the prevalence of rhabdomyolysis is low, instances still occur where exercise is improperly prescribed or used as punishment, or incomplete medical history is taken, and exertional rhabdomyolysis occurs. Creatine monohydrate does not appear to be a precipitating factor for exertional rhabdomyolysis. Healthcare professionals should be able to recognize the basic signs of exertional rhabdomyolysis so prompt treatment can be administered. For the risk of rhabdomyolysis to remain low, exercise testing and prescription must be properly conducted based on professional standards.
... Several studies have demonstrated that the loading phase is directly associated the weight gains experienced from CrM. This can be explained by water-retaining characteristics of CrM during the loading phase [4][5][6]2] . When skeletal muscles absorb ingested creatine, an osmotic gradient between the blood source and intracellular fluids is created; ultimately drawing water into the cells, increasing total body water [2] . ...
... The initial increase in fluid volume is associated with the loading phase of CrM supplementation; as the maintenance phase does not have the same impact on fluid distribution [5][6][7]11] . Therefore, the kidney fluid regulatory system will eventually counter fluid increase during the end of the loading phase within 3-5 days by excreting more water and salt, allowing for a decrease in extracellular volume and a return to homeostasis [8] . ...
... Studies reviewing the safety and efficacy of CrM have found it to be considered a "safe" nutritional supplement with weight gain as the only direct side effect [3,6,7,9,11,13,14] . This increase in weight occurs during the loading phase of supplementation (20-25 g x d -1 ) and can be partially attributed to the water retaining characteristics of CrM, which directly increases total body water [2,9,14,16,17] . ...
Creatine monohydrate (CrM) is considered a safe nutritional supplement. The loading phase of CrM supplementation is associated with shifts in total body water and plasma volume that may affect blood pressure. However, few studies have measured blood pressure during the loading phase of CrM supplementation. Purpose: The aim of this study was to determine if CrM supplementation in nor-motensive college-aged males induces a daily blood pressure increase during the supplementation-loading phase. Methods: Participants' blood pressure, shoulder extension active range of motion (AROM), arm girth, arm volume, plasma volume, blood volume, hematocrit, and hemoglobin were measured daily for five days of supplementation (4x5gxd-1 x5d) of either CrM (n=12) or placebo (P; n=12). Results: The CrM group did not experience significant changes in systolic blood pressure (mmHg) (CrM 126.67±1.94 Day5 ; P 125.50±2.61 Day5) or diastolic blood pressure (mmHg) (CrM 83.83±2.19 Day5 ; P 82.33±2.07 Day5) compared to P. A significant T x Tx interaction (p=0.001) and Tx effect (p=0.03) support decreased AROM (cm) in the CrM group compared to P (CrM 38.3±2.19 Day 1 , CrM 34.0±2.01 Day5 ; P 41.02±2.49 Day 1 , P 43.2±2.47 Day5). An increase in arm volume (ml) in the CrM group (CrM 2443±99.44 Day 1 , CrM 2470±92.21 Day5) vs. the P group (P 2372±74.44 Day 1 , P 2374±74.61 Day5 ; p=0.026) was observed. An increase in plasma volume (%Δ from baseline) (p=0.014) (CrM 1.48±2.60 Day2 , CrM 6.03±4.03 Day5 ; P 3.25±2.74 Day2 , P 5.05±2.91 Day5) and a decrease in hematocrit (%) (p=0.026) (CrM 0.47±0.01 Day 1 , 0.45±0.01 Day5 ; P 0.46±0.01 Day 1 , 0.45±0.01 Day5) were observed. Conclusion: Findings suggest CrM supplementation in the loading phase does not affect blood pressure in normotensive college-aged males. CrM reduces shoulder extension AROM presumably due to increased tissue volume secondary to fluid shifts.
... Likewise, Mayhew (2002) shows that creatine consumption of 5gr / day to 20gr / day for 0.25 to 5.6 years do not have a long-term adverse effect on the renal function index under study including urea serum and clearance of creatinine and creatinine in football players in America (Mayhew, Mayhew and Ware, 2002). Schilling (2001) shows that long-term creatine consumption (0.8 to 4 years) with an average loading of 13.7 ± 10.0gr / day and a maintenance dose of 9.7 ± 5.7gr / day can only increase creatinine serum concentration within the normal range (Schilling et al., 2001). ...
... Likewise, Mayhew (2002) shows that creatine consumption of 5gr / day to 20gr / day for 0.25 to 5.6 years do not have a long-term adverse effect on the renal function index under study including urea serum and clearance of creatinine and creatinine in football players in America (Mayhew, Mayhew and Ware, 2002). Schilling (2001) shows that long-term creatine consumption (0.8 to 4 years) with an average loading of 13.7 ± 10.0gr / day and a maintenance dose of 9.7 ± 5.7gr / day can only increase creatinine serum concentration within the normal range (Schilling et al., 2001). ...
The consumption of creatine supplement among amateur and professional athletes is increasing. The purpose of this study was to determine the effect of creatine supplementation on the kidney function of dragon boat athletes. 12 dragon boat athletes were divided into 2 groups, including one group that consumed creatine supplement and one group without creatine intake (placebo). Creatine supplement was given at a loading dose of 20gr/day. The frequency of creatine supplement intake was 3-4x a day. In the second week, the dose was reduced into 15 gr/day. Creatine supplements were consumed for 5 weeks. Blood urea and creatinine were taken from the median cubital vein of the arm by using a 3cc syringe. The results showed that creatine supplementation had a significant effect in increasing the level of blood urea and creatinine. Although there were increases in urea and creatinine levels in the blood, the amount was still within normal limits. Therefore, it should be anticipated by taking a sufficient water intake.
Abstrak
Konsumsi kreatin suplemen di kalangan atlet amatir dan profesional semakin meningkat. Tujuan dari penelitian ini adalah untuk mengetahui pengaruh suplemen kreatin terhadap fungsi ginjal atlet dragon boat. 12 orang atlet dragon boat dibagi menjadi 2 kelompok, satu kelompok yang mengkonsumsi kreatin dan satu kelompok tanpa asupan kreatin (placebo). Suplemen kreatin diberikan dengan dosis loading 20gr/hari, frekuensi pemberian 3-4x sehari. Pada minggu kedua dosis diturunkan menjadi 15 gr/hari. Suplemen kreatin dikonsumsi selama 5 minggu. Kadar ureum dan kreatinin darah diambil dari vena median cubital lengan dengan menggunakan spuit 3cc. Hasil penelitian didapatkan pemberian suplemen kreatin berpengaruh signifikan meningkatkan kadar ureum dan kreatinin dalam darah. Walau terdapat peningkatan kadar ureum dan kreatinin dalam darah namun jumlahnya masih dalam batas normal, sehingga perlu diantisipasi dengan asupan cairan yang memadai.
... 27 In contrast to most studies that reported no direct association between long-term creatine supplementation and kidney dysfunction, few investigations revealed a slight but not clinically significant elevation in serum creatinine. 16,27,28 For example, Schilling and coworkers demonstrated that long-term creatine consumption (0.8 to 4 years) with the mean loading of 13.7 ± 10.0 g/d and maintenance dose of 9.7 ± 5.7 g/d could only elevate the serum creatinine concentration within its normal range. 28 Apart from randomized or retrospective studies, 16,29 there is at least 1 case report suggesting a possible association between kidney dysfunction and creatine supplementation. ...
... 16,27,28 For example, Schilling and coworkers demonstrated that long-term creatine consumption (0.8 to 4 years) with the mean loading of 13.7 ± 10.0 g/d and maintenance dose of 9.7 ± 5.7 g/d could only elevate the serum creatinine concentration within its normal range. 28 Apart from randomized or retrospective studies, 16,29 there is at least 1 case report suggesting a possible association between kidney dysfunction and creatine supplementation. Taner and colleagues reported an 18-year-old man referred to the hospital with the chief complaint of nausea, vomiting, and gastric pain. ...
Introduction. Nowadays, creatine is one of the most common oral supplements used by professional athletes for boosting their strength and muscle mass. In this review, we collect available experimental and clinical data about renal safety of both short-term and long-term use of creatine.
Materials and Methods. Scientific literature was critically searched by keywords "creatine," "renal insufficiency," and "renal dysfunction" and their synonyms in medical databases (Scopus, MEDLINE, EMBase, and ISI Web of Knowledge). Overall, 19 relevant clinical and experimental articles were selected for this review.
Results. Short- and long-term creatine supplementations (range, 5 days to 5 years) with different doses (range, 5 g/d to 30 g/d) had no known significant effects on different studied indexes of kidney function such as glomerular filtration rate at least in healthy athletes and bodybuilders with no underlying kidney diseases. In addition, although short-term (range, 5 days to 2 weeks) high-dose oral creatine supplementation (range, 20 g/d to 0.3 g/kg/d) stimulated the production of methylamine and formaldehyde (as potential cytotoxic metabolites of creatine) in the urine of healthy humans, there was currently no definite clinical evidence about their adverse effects on the kidney function.
Conclusions. Although creatine supplementation appears to have no detrimental effects on kidney function of individuals without underlying kidney diseases, it seems more advisable to suggest that creatine supplementation not to be used by sportsmen or women with pre-existing kidney disease or those with a potential risk for kidney dysfunction.
... Additionally, the available evidence suggests that CM consumption is safe as long as it is consumed by following recommended protocols [3,[7][8][9][10]. Anecdotal reports from athletes have appeared on muscle cramps and gastrointestinal complaints during creatine supplementation, but the incidence is limited and not necessarily linked to creatine itself. ...
... Despite several unproved allegations, liver (enzymes, urea) and kidneys (glomerular filtration urea and albumin excretion rates) show no change in functionality in healthy subjects supplemented with creatine, even during several months [8,[10][11][12][13]. In a retrospective study, Schilling et al. [9] examined the effects of long lasting (up to 4 years) creatine monohydrate supplementation on health markers and did not notice any harmful effects (including muscle cramps or injuries) after long-term creatine consumption. Moreover, Dos Santos Pereira et al. [14] demonstrated that creatine do not have any carcinogenic effects on heterocyclic amine production in human subjects. ...
This review article aimed to summarize the current state of understanding on creatine supplementation for soccer players. In other words, it investigated the beneficial (and potentially negative) effects of this supplementation on sport-specific skills and performance in soccer players. Furthermore, this article accordingly discussed the safest and most recommended protocols for the consumption of creatine by these athletes.
... La administración de estas dosis de creatina se había realizado junto con hidratos de carbono ya que, como hemos expuesto, está demostrado que de esta manera la absorción del MC se incrementa (11,15). Los motivos por los que se utilizaron dosis bajas de creatina fueron el que no deseábamos un aumento excesivo de peso en los jugadores a los que se le administraba y por que, por los datos de estudios ya publicados (6)(7)21,26), conocíamos que no son necesarias dosis altas de creatina para conseguir los efectos ergogénicos de esta sustancia y que dosis superiores se relacionan con aparición de efectos secundarios (5-7, 21, 26-30). ...
... este resultado está en línea con los trabajos publicados por Grenwood y colaboradores (25,36), quienes mostraron como la ingesta de creatina en jugadores de rugby profesionales durante 3 temporadas no incrementó el número de lesiones musculares o calambres en comparación con atletas que no realizaron la ingesta. Los resultados del presente estudio y los publicados por Grenwood et al., aportan una mayor veracidad a los numerosos estudios que han propuesto que la suplementación con creatina no provoca los efectos adversos anteriormente sugeridos ni otros problemas de salud asociados (6)(7)10,21,30,37). en este sentido, se podría argumentar que la suplementación con MC permitiría a los atletas tolerar la carga de entrenamiento de una manera más eficiente y, en consecuencia, reduciría la incidencia de lesión. ...
Purpose: to study the incidence of sports injuries in first level soccer players supplemented with creatine monohydrate (MC). Methods: a retrospective study of control cases during a six month period was undertaken.Thirty males who play in a first level first soccer team were evaluated. Ten of the subjects were administered creatine monohydrate (MC) supplements while the other remaining 20 were used as control group. The study included the analysis of all injuries occurred in the team during the second half of the 2004-2005 season. Information was recorded on the type of injury, diagnosis, time to return to normal practice with the team and creatine monohydrate supplementation. Results: 43,37 injuries took place every thousand hours of competition in the group that received MC supplementation, whereas in the control group suffered 46,43 injuries every thousand hours of competition (p>0.05), being the competition times higher in the group with MC supplementation. As for the injury rate in relation to training time, the group that received MC showed 2,27 injuries every thousand hours of training whereas the control group showed 4,31 injuries every thousand hours of training (p<0,05). Conclusion: the supplementation with low doses of MC is a contributory factor to prevent muscle injuries in soccer players.
... Os dados do presente trabalho estão em conformidade com os estudos de Earnest et al. (15) , que não encontraram variações significativas das frações de bilirrubina quando a suplementação ocorreu com 20g/dia por cinco dias e 10g nos 51 dias restantes. Não foi encontrada nenhuma resposta diferente das já existentes na literatura em relação à função hepática (5,10,(15)(16)(17) . ...
... Ao analisar a função renal (16,26,27) e a função hepática (17,20,28) , tanto em curto prazo com altas doses quanto a longo prazo com baixas doses de suplementação de creatina, não observaram nenhuma disfunção. Bemben e Lammont (29) não relataram nenhum efeito adverso em revisão bibliográfica sobre os efeitos da suplementação com creatina em vários órgãos. ...
RESUMO A creatina é o suplemento nutricional mais popular utilizado para melhorar o desempenho em atividades que envolvem exercícios de curta duração e alta intensidade. Porém, as possíveis intercorrências advindas do seu uso não estão totalmente elucidadas. O objetivo do estudo foi avaliar os efeitos de duas dosagens de suplementação com creatina nas funções renal e hepática de adultos saudáveis durante oito semanas de treinamento de musculação. Exames bioquímicos foram realizados em 35 praticantes de musculação distribuídos aleatoriamente em três grupos, placebo (PLA, n = 12), creatina (CRE1, n = 12) e creatina 2 (CRE2, n = 11), antes e após oito semanas de treinamento com exercícios resistidos. Em desenho duplo-cego, os voluntários foram suplementados (20g/dia) com creatina (CRE1 e CRE2) ou placebo (PLA) por sete dias e nos 53 dias subsequentes com 0,03g/kg de massa corporal de creatina (CRE1) e placebo (PLA) e com 5g/dia o grupo CRE2. Não houve intervenção na composição de suas dietas, que foram registradas e analisadas. Os resultados dos exames bioquímicos realizados permaneceram dentro das faixas de normalidade. Os valores de creatinina aumentaram 12,2% no grupo CRE1 e 9,0%, no CRE2, enquanto que no grupo PLA diminuiu 4,7%, entretanto, esses valores não ultrapassaram os índices de normalidade. Os valores dos exames da função hepática diminuíram em quase todas as frações, em todos os tratamentos, contudo, sem significância estatística. Conclui-se que a suplementação com creatina nas dosagens utilizadas (0,03g/kg e 5g/dia) para indivíduos saudáveis por oito semanas não altera a função hepática ou renal, sendo assim, nas condições deste estudo, foi considerada segura. ABSTRACT Creatine is the most popular nutritional supplement widely used to improve performance in activities that involve exercise of short duration and high intensity. However, the complications arising from its use are not fully elucidated. The aim of this study was to evaluate the effects of two doses of creatine supple-mentation on renal and hepatic function in healthy adults during eight weeks of resistance exercise training. Biochemical tests were performed on 35 athletes randomly distributed into three groups, placebo (PLA, n = 12), creatine (CRE1, n = 12) and creatine2 (CRE2, n = 11) before and after eight weeks of resistance training. In a double-blind design, the volunteers were supplemented (20 g/day) with creatine (CRE1, CRE2) or placebo (PLA) for seven days and at the 53 subsequent days with 0.03g/kg of body weight of each supplement (CRE1, PLA) and 5g/day for CRE2. There was no intervention in the composition of their diets, which were recorded and analyzed. The results of biochemical tests conducted remained within normal ranges. Creatinine values increased by 12.2% for CRE1 and 9.0% for CRE2, whereas decreased by 4.7% in PLA; however, these values did not exceed normal rates. The values of liver function tests declined in nearly all fractions in all treatments, not being statistically significant, though. It is concluded that creatine supplementation at the dosages used (0.03g/kg and 5g/day) for healthy subjects during eight weeks does not alter hepatic or renal function, hence under the conditions of this study, creatine was considered safe.
... The data of the present study are in agreement with the studies by Earnest et al. (15) , which did not find significant alterations of the bilirubin fractions when supplementation occurred with 20g/ day for five days and 10g on the 51 remaining days. None responses different from the already existing in the literature about the hepatic function was found (5,10,(15)(16)(17) . ...
... Moreover, when the renal function (16,26,27) and hepatic function (17,20,28) , both in the short run with high doses and long run with low doses of creatine supplementation, did not observe any dysfunction. Bemben and Lammont (29) did not report any adverse effect in bibliographic review on the effects of creatine Table 7. Main indicators of the urine simple exam -EAS. ...
Creatine is the most popular nutritional supplement widely used to improve performance in
activities that involve exercise of short duration and high intensity. However, the complications arising
from its use are not fully elucidated. The aim of this study was to evaluate the effects of two doses
of creatine supplementation on renal and hepatic function in healthy adults during eight weeks of
resistance exercise training. Biochemical tests were performed on 35 athletes randomly distributed into
three groups, placebo (PLA, n = 12), creatine (CRE1, n = 12) and creatine2 (CRE2, n = 11) before and
after eight weeks of resistance training. In a double-blind design, the volunteers were supplemented
(20 g/day) with creatine (CRE1, CRE2) or placebo (PLA) for seven days and at the 53 subsequent days
with 0.03g/kg of body weight of each supplement (CRE1, PLA) and 5g/day for CRE2. There was no
intervention in the composition of their diets, which were recorded and analyzed. The results of biochemical
tests conducted remained within normal ranges. Creatinine values increased by 12.2% for
CRE1 and 9.0% for CRE2, whereas decreased by 4.7% in PLA; however, these values did not exceed
normal rates. The values of liver function tests declined in nearly all fractions in all treatments, not
being statistically significant, though. It is concluded that creatine supplementation at the dosages
used (0.03g/kg and 5g/day) for healthy subjects during eight weeks does not alter hepatic or renal
function, hence under the conditions of this study, creatine was considered safe.
... It is possible that other agents were also being consumed-though none were reported-or that excipients in the creatine preparations were the real culprits. In keeping with these possibilities, prolonged use of high maintenance doses of 9.7 ± 5.7 g/day for up to four years has been shown to have no apparent detrimental effects [44]. Similarly, creatine supplementation together with a high protein intake (1.2-3.1 g/kg/day) and resistance training had no apparent effect on creatinine clearance and albuminuria [45]. ...
Bodybuilders routinely engage in many dietary and other practices purported to be harmful to kidney health. The development of acute kidney injury, focal segmental glomerular sclerosis (FSGS) and nephrocalcinosis may be particular risks. There is little evidence that high protein diets and moderate creatine supplementation pose risks to individuals with normal kidney function though long-term high protein intake in those with underlying impairment of kidney function is inadvisable. The links between anabolic androgenic steroid use and FSGS are stronger, and there are undoubted dangers of nephrocalcinosis in those taking high doses of vitamins A, D and E. Dehydrating practices including diuretic misuse, and NSAID use also carry potential risks. It is difficult to predict the effects of multiple practices carried out in concert. Investigations into sub-clinical kidney damage associated with these practices have rarely been undertaken. Future re-search is warranted to identify clinical and subclinical harm associated with individual practices and combinations to enable appropriate and timely advice
... The gains in muscle mass appear to be a result of an improved ability to perform high intensity exercise enabling an athlete to train harder and thereby promote greater training adaptations and muscle hypertrophy [55][56][57] . The only clinically significant side effect reported from creatine supplementation has been weight gain 36,53,54,58 Although concerns have been raised about the safety and possible side effects of creatine supplementation 59, 60 , recent long-term safety studies have reported no apparent side effects 58,61,62 and/or that creatine may lessen the incidence of injury during training [63][64][65] . Consequently, supplementing the diet with creatine and/or creatine containing formulations seems to be a safe and effective method to increase muscle mass. ...
... The most effective way to increase muscle creatine stores is to ingest 5 g of creatine monohydrate (or approximately 0.3 g/kg body mass) 4 times daily for 5-7 days, followed by 3-5 g/day thereafter in order to maintain elevated creatine levels [3,15,37]. Creatine supplementation with long-term use appears to have no negative health effects in healthy individuals when appropriate loading protocols are followed [38,39]; however, a potential small increase in body mass after creatine loading as a result of water retention may be detrimental for sports with weight classes/restrictions or where an increased body mass may decrease performance, such as in longdistance and jumping events [3,40]. The WA Consensus Statement 2019 (Nutrition for Athletics) noted that creatine supplementation may help achieve a marginal performance gain in all TF disciplines except for middle-(1500 m) and long-distance events [41,42]. ...
Background:
While scientific evidence supports the efficacy of only limited nutritional supplements (NS) on sports performance, the use of NS is widespread in athletes. Given the serious issues of health damage or unintended Anti-Doping Rule Violations due to ingestion of contaminated NS in sports, accurately understanding NS practices by athletes is crucial. This study therefore elucidated the use of NS by elite Japanese track and field (TF) athletes.
Methods:
The subjects were 574 Japanese TF athletes, including 275 junior athletes (under 20 years) and 299 senior athletes, who participated in international competitions from 2013 to 2018. Data on NS use were collected through pre-participation medical forms obtained from all entrants before their participation in competitions. NS users were requested to report the product names and primary components of all NS they were taking.
Results:
The overall prevalence of NS use was 63.9%. The mean number of NS products used per athlete was 1.4. The prevalence was significantly higher in women (69.2%) than in men (59.6%) (p = 0.018) and significantly higher in senior athletes (68.9%) than in junior athletes (58.9%) (p = 0.012). The prevalence of NS use was higher in long-distance runners (75.8%) and lower in jumpers (52.3%) and throwers (49.2%) than other disciplines (p < 0.001). The most prevalent components were amino acids (49.3%), followed by vitamins (48.3%), minerals (22.8%), and protein (17.8%).
Conclusions:
Approximately two-thirds of elite Japanese TF athletes reported the use of NS, and NS practices varied by gender, age, and discipline.
... Serum creatinine remains the most commonly used biomarker of renal function and this corresponds to our review. Previous studies have shown no significant change in serum creatinine levels [94,135,[144][145][146][147][148][149], or a mild to modest change of up to 13% with creatine supplementation [150][151][152], which correlates with the ranges reported in our studies. Serum creatinine remained within normal range across all studies over the time of supplementation, and this finding corresponds with a previous review that found 91% of studies reported no change or change that remained within normal limits [87]. ...
Creatine Monohydrate (CrM) is a dietary supplement routinely used as an ergogenic aid for sport and training, and as a potential therapeutic aid to augment different disease processes. Despite its increased use in recent years, studies reporting potential adverse outcomes of CrM have been mostly derived from male or mixed sex populations. A systematic search was conducted, which included female participants on CrM, where adverse outcomes were reported, with meta-analysis performed where appropriate. Six hundred and fifty-six studies were identified where creatine supplementation was the primary intervention; fifty-eight were female only studies (9%). Twenty-nine studies monitored for adverse outcomes, with 951 participants. There were no deaths or serious adverse outcomes reported. There were no significant differences in total adverse events, (risk ratio (RR) 1.24 (95% CI 0.51, 2.98)), gastrointestinal events, (RR 1.09 (95% CI 0.53, 2.24)), or weight gain, (mean difference (MD) 1.24 kg pre-intervention, (95% CI −0.34, 2.82)) to 1.37 kg post-intervention (95% CI −0.50, 3.23)), in CrM supplemented females, when stratified by dosing regimen and subject to meta-analysis. No statistically significant difference was reported in measures of renal or hepatic function. In conclusion, mortality and serious adverse events are not associated with CrM supplementation in females. Nor does the use of creatine supplementation increase the risk of total adverse outcomes, weight gain or renal and hepatic complications in females. However, all future studies of creatine supplementation in females should consider surveillance and comprehensive reporting of adverse outcomes to better inform participants and health professionals involved in future trials.
... Cr as an oral supplement is considered safe and ethical, the perception of safety cannot be guaranteed, especially when administered for long period of time to different populations (athletes, sedentary, patient, active, young or elderly [2]. Thus Cr supplementation is a safe practice when administered within the recommended criteria [10,25,109,[116][117][118]. Nevertheless a possible unexpected outcome related to CrM ingestion is the amount of contaminants present that may be generated during the industrial production [119]. ...
... Estudos clínicos avaliando possíveis efeitos da suplementação com creatina sobre o fígado ainda deixam muitas dúvidas, não permitindo uma afi rmação de que a suplementação com creatina leva a alterações hepáticas, principalmente por se tratar de relatos de casos e estudos retrospectivos [49,50]. ...
Enquanto o consumo de creatina por atletas e praticantes de atividade física que desejam aumentar a massa muscular e o desempenho físico tem crescido vertiginosamente, os efeitos adversos desse suplemento continuam sendo alvos de debates. O objetivo desta revisão é descrever aspectos gerais da creatina, seu metabolismo e impacto na composição corporal. Enfatizam-se possíveis efeitos colaterais prejudiciais, em especial sobre a função renal e hepática. Há muitas contradições e lacunas na literatura, fatores que contribuem para a divergência do tema, uma vez que os resultados disponíveis são contraditórios. Levando-se em conta que estudos sobre possíveis efeitos tóxicos da suplementação com creatina são escassos, sugere-se investimento adicional para avaliar a relação custo-benefício de sua suplementação.
... While creatine supplementation appears relatively "safe" (Poortmans and Francaux 1999;Schilling et al. 2001;Mayhew et al. 2002), there has been no critical evaluation of its health implications following long-term use in children and adolescent athletes. A most recent news release by the American Academy of Pediatrics (Rogers 2007) titled "Creatine use by adolescents not recommended due to limited data" outlines several concerns regarding the use of creatine by adolescent athletes, these include; ...
... At present, there are no clinically significant side effects reported following CM supplementation at recommended doses, unlike weight gain-an attribute often required by many athletes and subjects affected by muscle diseases (Bender et al., 2008;Dalbo et al., 2008;Kreider et al., 2003a;Schilling et al., 2001). ...
... No negative health effects have been noted with the long-term use of CM (up to 4 years) when appropriate loading protocols are followed (Schilling et al., 2001), and in some instances, potential anti-inflammatory effects are proposed (Deminice et al., 2013). Therefore, creatine supplementation consumed according to the aforementioned protocols, shows strong efficacy for both acute and chronic performance gains where power, strength and short repeated bouts of high-intensity exercise are encountered. ...
Athletes are exposed to numerous nutritional products, attractively marketed with claims of optimizing health, function and performance. However, there is limited evidence to support many of these claims, and the efficacy and safety of many products is questionable. The variety of nutritional aids considered for use by track and field athletes includes sports foods, performance supplements and therapeutic nutritional aids. Support for sports foods, and five evidence-based performance supplements (caffeine, creatine, nitrate/beetroot juice, beta-alanine and bicarbonate) varies according to the event, the specific scenario of use and the individual athlete's goals and responsiveness. Specific challenges include developing protocols to manage repeated use of performance supplements in multi-event or heat-final competitions or the interaction between several products which are used concurrently. Potential disadvantages of supplement use include expense, false expectancy and the risk of ingesting banned substances sometimes present as contaminants. However, a pragmatic approach to the decision-making process for supplement use is recommended. We conclude that it is pertinent for sports foods and nutritional supplements to be considered only where a strong evidence-base supports their use as safe, legal and effective; and that such supplements are trialed thoroughly by the individual before committing to use in a competition setting.
... The only clinically significant side effect occasionally reported from creatine monohydrate supplementation has been the potential for weight gain [181,182,187,188]. Although concerns have been raised about the safety and possible side effects of creatine supplementation [189,190], multiple shorter [191][192][193] and long-term safety studies have reported no apparent side effects [188,194,195] and/or that creatine monohydrate may lessen the incidence of injury during training [196][197][198][199]. Consequently, supplementing the diet with creatine monohydrate and/or creatine containing formulations seems to be a safe and effective method to increase muscle mass. The ISSN position stand on creatine monohydrate [10] summarizes their findings as this: ...
Background:
Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words 'sport nutrition'. Consequently, staying current with the relevant literature is often difficult.
Methods:
This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches.
Conclusions:
This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.
... No negative health effects are noted with long-term use (up to 4 years) when appropriate loading protocols are followed. 67 A potential 1-2 kg BM increase after creatine loading (primarily as a result of water retention 66 68 ) may be detrimental for endurance performance or in events where the BM must be moved against gravity (eg, high jump, pole vault) or where athletes must achieve a specific BM target. ...
Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition program. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including the management of micronutrient deficiencies, supply of convenient forms of energy and macronutrients, and provision of direct benefits to performance or indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can offer benefits to the athlete, but others may be harmful to the athlete's health, performance, and/or livelihood and reputation if an anti-doping rule violation results. A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome, and habitual diet. Supplements intended to enhance performance should be thoroughly trialed in training or simulated competition before implementation in competition. Inadvertent ingestion of substances prohibited under the anti-doping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount, and expert professional opinion and assistance is strongly advised before embarking on supplement use.
... No negative health effects are noted with long-term use (up to 4 years) when appropriate loading protocols are followed. 67 A potential 1-2 kg BM increase after creatine loading (primarily as a result of water retention 66 68 ) may be detrimental for endurance performance or in events where the BM must be moved against gravity (eg, high jump, pole vault) or where athletes must achieve a specific BM target. ...
Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition programme. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including (1) the management of micronutrient deficiencies, (2) supply of convenient forms of energy and macronutrients, and (3) provision of direct benefits to performance or (4) indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can benefit the athlete, but others may harm the athlete’s health, performance, and/or livelihood and reputation (if an antidoping rule violation results). A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome and habitual diet. Supplements intended to enhance performance should be thoroughly trialled in training or simulated competition before being used in competition. Inadvertent ingestion of substances prohibited under the antidoping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete’s health and awareness of the potential for harm must be paramount; expert professional opinion and assistance is strongly advised before an athlete embarks on supplement use.
... Interestingly, concurrent consumption of CM with a mixed protein/carbohydrate source (∼50 g of protein and carbohydrate) appears to enhance muscle creatine uptake via an insulin-mediated effect ( Steenge et al., 2000), suggesting that creatine doses are best taken with a meal (or separate food supplement). No negative health effects have been reported with the long-term use of CM (up to 4 years) when appropriate loading protocols are followed ( Schilling et al., 2001). In fact, some reports propose CM supple- mentation to be anti-inflammatory, and to reduce exercise-induced oxidative stress (Deminice et al., 2013). ...
A strong foundation in physical conditioning and sport-specific experience, in addition to a bespoke and periodized training and nutrition program, are essential for athlete development. Once these underpinning factors are accounted for, and the athlete reaches a training maturity and competition level where marginal gains determine success, a role may exist for the use of evidence-based performance supplements. However, it is important that any decisions surrounding performance supplements are made in consideration of robust information that suggests the use of a product is safe, legal, and effective. The following review focuses on the current evidence-base for a number of common (and emerging) performance supplements used in sport. The supplements discussed here are separated into three categories based on the level of evidence supporting their use for enhancing sports performance: (1) established (caffeine, creatine, nitrate, beta-alanine, bicarbonate); (2) equivocal (citrate, phosphate, carnitine); and (3) developing. Within each section, the relevant performance type, the potential mechanisms of action, and the most common protocols used in the supplement dosing schedule are summarized.
... The same study states that creatine monohydrate is still the most used form of creatine supplementation. Finally, long-term creatine use does not appear to result in adverse health effects, at least while consuming the most popular creatine forms [246,284]. ...
Contemporary elite soccer features increased physical demands during match-play, as well as a larger number of matches per season. Now more than ever, aspects related to performance optimization are highly regarded by both players and soccer coaches. Here, nutrition takes a special role as most elite teams try to provide an adequate diet to guarantee maximum performance while ensuring a faster recovery from matches and training exertions. It is currently known that manipulation and periodization of macronutrients, as well as sound hydration practices, have the potential to interfere with training adaptation and recovery. A careful monitoring of micronutrient status is also relevant to prevent undue fatigue and immune impairment secondary to a deficiency status. Furthermore, the sensible use of evidence-based dietary supplements may also play a role in soccer performance optimization. In this sense, several nutritional recommendations have been issued. This detailed and comprehensive review addresses the most relevant and up-to-date nutritional recommendations for elite soccer players, covering from macro and micronutrients to hydration and selected supplements in different contexts (daily requirements, pre, peri and post training/match and competition).
... The patient received high-dose supplementation with Cr (20 g/day) for 5 days followed by Cr (5 g/day) for 30 days without negatively affecting his kidney function [71]. A retrospective study of long-term high-dose Cr supplementation (13 g Cr/day for up to 4 years) that assessed 65 variables, including independent clinical markers for kidney function, did not observe untoward health effects, except for occasional gastrointestinal upset [72]. Notably, a double-blinded, placebo-controlled clinical study of 18 healthy participants who received 10 g of Cr per day for 3 months found a slight but significant increase in the glomerular filtration rate for the participants receiving Cr versus the controls, as measured by the cystatin clearance method [73]. ...
The CK/PCr-system, with creatine (Cr) as an energy precursor, plays a crucial role in cellular physiology. In the kidney, as in other organs and cells with high and fluctuating energy requirements, energy-charged phospho-creatine (PCr) acts as an immediate high-energy source and energy buffer, and as an intracellular energy transport vehicle. A maximally filled total Cr (Cr plus PCr) pool is a prerequisite for optimal functioning of the body and its organs, and health. Skeletal- and cardiac muscles of dialysis patients with chronic kidney disease (CKD) are depleted of Cr in parallel with the duration of dialysis. The accompanying accumulation of cellular damage seen in CKD patients lead to a deterioration of musculo-skeletal and neurological functioning and poor quality of life (QOL). Therefore, to counteract Cr depletion, it is proposed to supplement CKD patients with Cr. The anticipated benefits include previously documented improvements in the musculo-skeletal system, brain and peripheral nervous system, as well as improvements in the common comorbidities of CKD patients (see below). Thus, with a relatively simple, safe and inexpensive Cr supplementation marked improvements in quality of life (QOL) and life span are likely reached. To avoid Cr and fluid overload by oral Cr administration, we propose intradialytic Cr supplementation, whereby a relatively small amount of Cr is added to the large volume of dialysis solution to a final concentration of 1-10mM. From there, Cr enters the patient’s circulation by back diffusion during dialysis. Because of the high affinity of the Cr transporter (CRT) for Cr affinity for Cr (Vmax of CRT for Cr = 20-40 μM Cr), Cr is actively transported from the blood stream into the target cells and organs, including skeletal and cardiac muscle, brain, proximal tubules of kidney epithelial cells, neurons, and leukocytes and erythrocytes, which all express CRT and depend on the CK/PCr system. By this intradialytic strategy, only as much Cr is taken up by the body as is needed to fill the tissue Cr pools and no excess Cr has to be excreted, as is the case with oral Cr. Because aqueous solutions of Cr are not very stable, Cr must be added immediately before dialysis either as solid Cr powder or from a frozen Cr stock solution to the dialysate, or alternatively, Cr could become an additional component of a novel dry dialysate mixture in a cartridge device.
... The gains in muscle mass appear to be a result of an improved ability to perform high intensity exercise enabling an athlete to train harder and thereby promote greater training adaptations and muscle hypertrophy [72][73][74][75]. The only clinically significant side effect occasionally reported from creatine monohydrate supplementation has been the potential for weight gain [71,[76][77][78] Although concerns have been raised about the safety and possible side effects of creatine supplementation [79,80], recent longterm safety studies have reported no apparent side effects [78,81,82] and/or that creatine monohydrate may lessen the incidence of injury during training [83][84][85]. Additionally a recent review was published which addresses some of the concerns and myths surrounding creatine monohydrate supplementation [86]. ...
Abstract Sport nutrition is a constantly evolving field with literally thousands of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper presents a well-referenced overview of the current state of the science related to how to optimize training through nutrition. More specifically, this article discusses: 1.) how to evaluate the scientific merit of nutritional supplements; 2.) general nutritional strategies to optimize performance and enhance recovery; and, 3.) our current understanding of the available science behind weight gain, weight loss, and performance enhancement supplements. Our hope is that ISSN members find this review useful in their daily practice and consultation with their clients.
... An increase in body mass associated with creatine supplementation has been suggested to be an unwanted side effect by some individuals (Schilling et al., 2001). For most athletes supplementing with creatine, weight gain is often a desired outcome. ...
Creatine and beta-alanine are two of the most popular sport supplements used by strength/power athletes today. The popularity of creatine has resulted in more than 600 studies examining the physiology, efficacy and safety of its use among various athletic populations. Recently, beta-alanine has become as popular a supplement for the anaerobic athlete due to its unique ability to enhance muscle buffering capacity. This review examine the studies that have been conducted on the efficacy of these supplements. In addition, the physiology that underlies the mechanisms of action behind these supplements will be described and provide an understanding to the potential ergogenic benefits that they hold for strength and power athletes. Finally, discussion will also examine the potential adverse effects associated with each supplement.
... In addition, long term CrS (5 g/day during 21 months) does not negatively affect athletes' health nor caused any clinically significant change in serum metabolic markers, muscle and liver enzyme efflux, serum electrolytes, blood lipid profiles, red and white whole blood cell hematology, or quantitative and qualitative urinary markers[145]. In addition, this research supports previous reports from short-term studies (5 days-12 weeks) and long term retrospective studies of athletes (up to 5 years) that found no adversely effects in athletes, healthy individuals and patient populations[60,136,[146][147][148][149][150]. ...
Creatine is one of the best-known and most studied ergogenic supplements among athletes. Besides its performance-enhancing power, creatine has significant clinical potential in patients with neurological and neuromuscular diseases. The most frequently used form of creatine is creatine monohydrate. The utilization of creatine monohydrate seems to be somewhat limited due to its physico-chemical characteristics such as poor water solubility, instability in aqueous solutions (because of its tendency to cyclize into biologically inactive creatinine), and finite capacity of creatine transporters. Therefore, the pharmaceutical industry strives to develop novel forms of creatine that will diminishor overcome aforementioned limitations. New formulations of creatine seem to appear inthe market on a daily basis while no sufficient research is conducted regarding their physico-chemical characteristics and safety in humans. In this chapter, authors reviewed recent literature on advanced creatine formulations (e.g., creatine salts, chelates, estersand alkaline buffered forms). The purpose and goal for the use of new creatine formulations have been discussed as well as their advantages and disadvantages compared to creatine monohydrate
... previous studies. [18][19][20] Compared with placebo, a slight (1-1.5 kg) increase in body weight was found after medium term creatine supplementation. This has also been reported in most previous studies. ...
The aim of the study was to determine the effects of creatine supplementation on tennis performance and various health parameters. This was an experimental, double blind study that was placebo-controlled. A total of 36 competitive tennis players (24 with creatine supplementation, 12 with placebo) of International Tennis No. 3 status or higher were tested three times on two successive days: before the study, after six days of creatine loading and after a maintenance phase of four weeks (14 with creatine supplementation, 10 with placebo). On the test days, the players served ten times, as fast and accurately as possible. This was followed by balls hit down the lines, consisting of three series of five times eight strokes (alternating forehand and backhand), with the player sprinting along the baseline. The velocity of all strokes was measured. The next day the strength of the arms and legs was measured in repetitive maximal bench press and leg press tests. Subsequently, three series of five 20m sprints were performed. The level of general and muscular well-being was recorded through questionnaires. Various health parameters were examined, using biometry and blood and urine samples. No performance-enhancing effect of creatine supplementation was found on service velocity, velocity of the ground strokes, repetitive sprinting velocity of the strength of the upper and lower extremities. Body weight increased significantly in the creatine group compared to the placebo group (1.4±1,0 vs. -0.24±2.0 kg. P<0.05). Creatine was not found to have any effect on the various health parameters.
... Schilling et al. [77] examined the long-term (0.8-4 yr) safety of Cr supplementation in 26 competitive athletes (18 male and 8 females, 24.7±9.2 yr) and found no evidence of increased incidence of muscle injury, cramps, or any other side effects. ...
Limb immobilization (casting) results in a loss of muscle mass along with decrements in muscle strength and endurance. In addition, immobilization has been shown to impair high energy phosphate catabolism in skeletal muscle. Creatine ingestion in conjunction with resistance training can significantly increase muscle force production, augment muscle size increases, and improve energy-rich phosphate catabolism in skeletal muscle. Surprisingly, there are few research studies investigating the potential of oral creatine supplementation to mitigate the muscle changes during immobilization. Early investigations found that creatine supplementation can maintain muscle size, strength, and endurance during short-term (1-2 wk) immobilization. Future research should focus on whether creatine supplementation can also prevent muscle metabolic consequences during immobilization. Creatine ingestion during short-term immobilization may help to identify the underlying mechanisms that contribute to the reported ergogenic effects.
... Estudos realizados em indivíduos com deficiência da síntese de creatina não apontaram efeitos colaterais em períodos prolongados de utilização 67,82 . Já estudos com outras populações sugerem que a suplementação de creatina não prejudica a função renal 30,55,73,74,90 , hepática 83 e do sistema cardiovascular 48 , bem como inúmeros marcadores de saúde 12,62,65 . ...
Creatine was discovered more than one century ago, but its use became importantin sports scenario in the 70’s. Since then, the improvement in knowledge and utilization protocolsmade this substance the licit ergogenic aid most studied and used by athletes nowadays. Thebenefits of supplementation in athletes served as a model for studies in diseased individuals,that present ATP synthesis or ressynthesis deficiency, neurological and muscular diseases,or that suffer from muscular atrophy or impairment of muscular metabolism
... Schilling et al (2001) conducted a retrospective study to examine markers related to health, the incidence of reported side effects and the perceived training benefits in athletes supplementing with creatine monohydrate.Various clinical examinations were performed and a questionnaire completed regarding dietary habits, creatine supplementation, medical, and training history, and perceived effects of supplementation. Subjects were grouped They conclude that the means of all variables within each group fell within normal clinical ranges. ...
... In addition, there is an increasing body of literature indicating that creatine supplementation may also be an effective clinical treatment for various neuromuscular (Felber, Skladal, Wyss, Kremser, Koller, & Sperl, 2000), neurological (Matthews, Yang, Jenkins, Ferrante, Rosen, Kaddurah-Daouk, et al., 1998), and cardiovascular (Saks & Strumia, 1993) diseases, as well as a role as an anticancer agent (Martin, Winslow, & Kaddurah-Daouk, 1994). Lastly, there have been no clinically significant safety concerns or side effects reported with creatine supplementation (Farquhar & Zambraski, 2002;Greenwood, Kreider, Melton, Rasmussen, Lancaster, Cantler, et al., 2003;Kreider, Melton, Rasmussen, Greenwood, Lancaster, Cantler, et al., 2003;Poortmans & Francaux, 2000;Schilling, Stone, Utter, Kearney, Johnson, Coglianese, et al., 2001). ...
Thesis Chairperson: Darryn S. Willoughby, Ph.D. Creatine monohydrate has become one of the most popular ingested nutritional supplements used for its potential to enhance athletic performance. Numerous creatine formulations have been developed to maximize creatine absorption, and may also provide a means to either partially bypass or up-regulate the function of creatine transporter-1 (CreaT1). Cinnamon extract (Cinnulin TM) has been observed to mimic the effects of insulin, thereby up-regulating glucose uptake and insulin signaling. This study examined how a seven-week supplementation regimen with creatine monohydrate combined with Cinnulin TM (CCI), creatine monohydrate (CR), or placebo (PLA) affected physiological and molecular adaptations in nonresistance-trained males following a prescribed resistance-training program. Results demonstrated that Cinnulin TM combined with creatine monohydrate elicited greater mean increases in relative 1-RM leg press, thigh lean mass, body water, and total Akt protein content when compared to creatine monohydrate alone, or placebo; however, intramuscular creatine increases between the CCI and CR groups demonstrated no significant differences.
Context:
Many clinicians, trainers, and athletes do not have a true understanding of the effects of commonly used performance-enhancing drugs (PEDs) on performance and health.
Objective:
To provide an evidence-based review of 7 commonly used pharmacological interventions for performance enhancement in athletes.
Data sources:
PubMed and Scopus databases were searched on April 8, 2022.
Study selection:
Systematic reviews (SRs) and meta-analyses (MAs) assessing the performance-enhancing effects of the following interventions were included: androgenic anabolic steroids (AAS), growth hormone (GH), selective androgen receptor modulators (SARMs), creatine, angiotensin-converting enzyme (ACE)-inhibitors, recombinant human erythropoietin (rHuEPO), and cannabis.
Study design:
Umbrella review of SRs and MAs.
Level of evidence:
Level 4.
Data extraction:
Primary outcomes collected were (1) body mass, (2) muscle strength, (3) performance, and (4) recovery. Adverse effects were also noted.
Results:
A total of 27 papers evaluating 5 pharmacological interventions met inclusion criteria. No studies evaluating SARMs or ACE-inhibitors were included. AAS lead to a 5% to 52% increase in strength and a 0.62 standard mean difference in lean body mass with subsequent lipid derangements. GH alters body composition, without providing a strength or performance benefit, but potential risks include soft tissue edema, fatigue, arthralgias, and carpel tunnel syndrome. Creatine use during resistance training can safely increase total and lean body mass, strength, and performance in high-intensity, short-duration, repetitive tasks. Limited evidence supports rHuEPO benefit on performance despite increases in both VO2max and maximal power output, and severe cardiovascular risks are documented. Cannabis provides no performance benefit and may even impair athletic performance.
Conclusion:
In young healthy persons and athletes, creatine can safely provide a performance-enhancing benefit when taken in controlled doses. AAS, GH, and rHuEPO are associated with severe adverse events and do not support a performance benefit, despite showing the ability to change bodily composition, strength, and/or physiologic measures. Cannabis may have an ergolytic, instead of ergogenic, effect.
RuBisCO is a complete protein, widely abundant and recognized as ideal for human consumption. Further, its biochemical composition, organoleptic and physical features mean RuBisCO has potential as a nutritionally beneficial food additive. Nonetheless, despite growing plant-based market trends, there is a lack of information about the applications of this protein. Here, we explored the biochemical features of RuBisCO as a potential food additive and compared it with other plant protein sources currently available. We describe potential advantages, including nutritional content, digestibility, non-allergenicity and, potential bioactivities. Despite the lack of industrial procedures for RuBisCO purification, a growing number of novel methods are emerging, justifying discussion of their feasibilities. Overall, this information can help both researchers and industry to review the use RuBisCO as a sustainable source of protein for plant-based food products or formulation of novel functional foods.
This chapter presents a case scenario of a 16‐year‐old male, who asks orthopedic specialists about creatine supplementation. The most common legal performance enhancing supplements used by athletes are creatine, protein powders, and caffeine. Creatine is predominately stored in skeletal muscle where it serves as the energy substrate for muscle contraction. Changes in myogenic transcription factors occur when creatine supplementation and resistance training are combined in young healthy males. It was observed that serum levels of myostatin, a muscle growth inhibitor, were decreased in the creatine group. The current consensus is to recommend against creatine use in athletes with existing renal disease. Creatine supplementation may be effective as an ergogenic aid in short bouts of intense exercise. The chapter provides recommendations for implementing evidence‐based practice in the clinical setting.
Objectivo: Défices ou excessos nutricionais podem impedir o máximo rendimento de um desportista. Assim, estudamos a ingestão nutricional de um maratonista de elite, analisando o grau de adequação às exigências de treino e competição. Material e métodos: Maratonista de elite (32 anos, 1,69m, 55 kg), 4º lugar no Campeonato do Mundo de Atletismo, (2h09’28” - melhor marca pessoal). Realiza 12 a 14 treinos por semana. Os dados nutricionais foram obtidos por registo de sete dias. A conversão dos alimentos em nutrientes foi realizada pelo programa informático The Food Processor Plus 7.0. Estatística: Utilizaram-se as medidas descritivas, média, desvio-padrão e valores máximo e mínimo dos sete dias. Resultados: Aporte diários médios: calorias - 2296 ± 639 Kcal; carbohidratos – 40,6 ± 10,2% (4,42 ± 1,98 g/kg/dia); proteínas - 22,9 ± 6,7% (2,1 ± 0,3 g/kg/dia); gorduras – 36,5 ± 6,3%; colesterol – 488,1 ± 102,3 mg; fibras – 8,1 ± 2,8 g; vitamina C – 24,9 ± 12,5 mg; vitamina A – 211,0 ± 130,5 μg ER; Betacaroteno – 163,4 ± 265,5 μg; vitamina D – 3,7 ± 4,1 μg; vitamina E – 7,02 ± 3,4 mg ET. Reduzido aporte de cálcio (387,4 ± 154,5 mg), magnésio (222,6 ± 22,3 mg), molibdénio (2,46 ± 3,42 μg) e iodo (58,6 μg). Conclusão: Este maratonista apresenta um perfil nutricional incompatível com as elevadas exigências do treino e competição, caracterizado pelo reduzido aporte de energia, carboidratos, vitaminas antioxidantes e fibras, com excessivo consumo de colesterol. Este maratonista deve alterar o seu perfil de ingestão nutricional.Palavras-chave: perfil nutricional, esportes, provas de rendimento.
Sports supplements can be generally divided into 3 categories: sports foods (foods/drinks containing macronutrients), medical supplements (vitamins/minerals used to treat deficiencies), and ergogenic supplements (used to benefit performance). Supplements are not regulated by the US Food and Drug Administration. They may get to the market and be contaminated with substances banned in sport or dangerous to health; and the contents may not contain what is listed on the label. When choosing to use a supplement, the safest practice is to choose a certified brand, which tests and authenticates label verification, quality, and lack of contaminants and banned substances for sport.
With regard to athletes attempting to improve their performance, at the present time creatine monohydrate is clearly the most widely used dietary supplement or ergogenic aid. Loading doses as high as 20 g/d are typical among athletes. The majority (> 90%) of the creatine ingested is removed from the plasma by the kidney and excreted in the urine. Despite relatively few isolated reports of renal dysfunction in persons taking creatine, the studies completed to date suggest that in normal healthy individuals the kidneys are able to excrete creatine, and its end product creatinine, in a manner that does not adversely alter renal function. This situation would be predicted to be different in persons with impaired glomerular filtration or inherent renal disease. The question of whether long-term creatine supplementation (ie, months to years) has any deleterious affects on renal structure or function can not be answered at this time. The limited number of studies that have addressed the issue of the chronic use of creatine have not seen remarkable changes in renal function. However, physicians should be aware that the safety of long-term creatine supplementation, in regard to the effects on the kidneys, cannot be guaranteed. More information is needed on possible changes in blood pressure, protein/albumin excretion, and glomerular filtration in athletes who are habitual users of this compound.
Although dietary supplements offer consumers the ability to participate in their own health and well being, steps need to be taken to educate the public and clinicians to prevent misuse and encourage proper use. Better patient education through health care providers and the establishment of good manufacturing procedures for supplement producers will benefit those wishing to take dietary supplements. Currently, supplement users may be exposed to increased risk due to the lack of required good manufacturing procedures, poor communication between patients and health care providers, and the manner in which dietary supplements can be marketed without proof of safety or efficacy derived from large clinical trials.
The primary factors that affect exercise performance capacity include an individual’s genetic endowment, the quality of training, and effective coaching (see Fig. 19.1). Beyond these factors, nutrition plays a critical role in optimizing performance capacity. In order for athletes to perform well, their training and diet must be optimal. If athletes do not train enough or have an inadequate diet, their performance may be decreased [1]. On the other hand, if athletes train too much, without a sufficient diet, they may be susceptible to becoming overtrained (see Fig. 19.2).
Member States requested the European Food Safety Authority (EFSA) to provide opinions relating to the food ingredient creatine and a range of health claims. The EFSA Panel provided a positive opinion on creatine and exercise performance, stating it was effective for 'increasing physical performance during short-term, high intensity, repeated exercise bouts'. However, some data relating to creatine's effects on strength and muscle mass were not addressed in this assessment. Hence the only authorised EU health claim for creatine is: 'Creatine increases physical performance in successive bursts of short-term, high intensity exercise'.
Anecdotal reports suggest that creatine supplementation during intense training and competition may increase the incidence of muscle cramping and injury. This study examined the effects of creatine supplementation on cramping and injury during collegiate baseball training and competition. Thirty-nine Division I baseball players participated in this study. Twenty-one (54.0%) of the thirty-nine athletes ingested 15 to 25g/d of creatine for 5 days followed by 5 g/day of creatine that was mixed with sports drinks or water. Athletes who were non-creatine users had access to a carbohydrate drink that contained no creatine (placebo) during the training/competition period. Injuries treated by the athletic training staff were recorded and categorized as cramping, heat/dehydration, muscle tightness, muscle strains, non-contact injuries joint injuries, contact injuries, and illness. The number of practices missed due to injury and illness were also recorded. While no heat/dehydration events were reported by either group, results revealed that creatine-users had significantly fewer total injuries, ?2 (1)=4.69, p=0.03 than non-creatine users (p<0.05). However, there were no significant differences between groups regarding cramping, ?2 (1)=2.94, p=0.08, muscle tightness, ? 2 (1)=3.01, p=0.08, muscle strains, ?2 (1)=2.92, p=0.08, non-contact joint injuries, ?2 (1)=1.04, p=0.31, contact injuries, ?2 (1)=0.009, p=.92, illness, ?2 (1)=0.02, p=0.95, missed practices due to injury, ?2 (1)=.103, p=0.74, and players lost for the season, ?2 (1)=2.45, p=0.11. Based on the findings in this investigation, creatine supplementation during collegiate baseball training and competition does not appear to increase the incidence of injury or cramping. Additional research is warranted to evaluate the effect of creatine supplementation on athletes training in hot/humid climates.
Without question, since its over the counter availability to consumers in 1992, creatine has become one of the most popular nutritional supplements among exercise and sport populations. In addition to its popularity, creatine has become one of the most extensively studied and research validated products that have been experimentally dissected in a multitude of ways. Specifically, investigators have evaluated topics such as muscle-creatine content and phosphocreatine resynthesis, short-and long-term ergogenic effects of creatine ingestion, gender issues associated with creatine ingestion, age-specific issues related to creatine ingestion, ethical considerations of creatine ingestion, viable clinical and medical applications of creatine ingestion, health and safety concerns regarding creatine ingestion, and more recently relevant biochemical mechanisms regarding the creatine transport system. Although each of these research approaches have greatly contributed to the body of creatine literature, it is first imperative to grasp various foundational aspects associated with understanding this controversial nutritional supplement. With these considerations in mind, the purpose of this chapter is to set the stage for a creatine overview regarding the following information: (1) creatine facts, fallacies, and safety (2) creatine quality, purity, and formulations, (3) creatine dosage protocols, (4) creatine nutritional supplement combinations, (5) foundational creatine ergogenic efficacy, (6) future creatine research options, and (7) common creatine practical applications.
Creatine remains one of the most extensively studied nutritional ergogenic aids available for athletes. Hundreds of studies have reported that increasing muscle creatine stores through creatine supplementation can augment muscle creatine content, improve exercise and training adaptations, and/or provide some therapeutic benefit to some clinical populations. Consequently, creatine represents one of the most effective and popular nutritional ergogenic aids available for athletes. The future of creatine research is very promising. Researchers are attempting to determine ways to maximize creatine storage in the muscle, which types of exercise may obtain the greatest benefit from creatine supplementation, the potential medical uses of creatine, and the long-term safety and efficacy of creatine supplementation. Among these, the most promising area of research is determining the potential medical uses of creatine, particularly in patients with creatine synthesis deficiencies and neuromuscular diseases. Nevertheless, in regard to athletes, creatine has continually proved itself to be one of the most effective and safe nutritional supplements to increase strength, muscle mass, and performance. This is despite oftentimes inaccurate and misleading information that has been written about creatine in the popular media over the last several years.
In the last few decades, the use of ergogenic aids has become widespread among professional and amateur athletes. There are several reasons for this, including changes in the way dietary supplements are marketed, the growing body of research, and increased financial rewards for stand-out athletes. It is important for physicians, athletic trainers, and coaches to have a solid working knowledge about the risks, benefits, and efficacy of common supplements in order to ensure effective and honest communication with athletes.
This study was conducted to investigate the effects of creatine loading and resistance training on the homocysteine and lipid profiles of young males.
Sixty male University students (22.34±2.19 years, 1.79±0.08 m, 77.18±12.57 kg, 15.48±4.57% body fat) were randomly divided in to three groups; control (CG=20), creatine supplement (CEG=20) and placebo (PEG=20). Both CEG and PEG participated in a same resistance-training regimen and either taking a creatine supplement (25 g/d for the first 5 days followed 5 g/d thereafter) or the same amount of placebo for 8 weeks. Participants in CG did not take any creatine supplementation and not engage any exercise program. After the body composition were assessed, the homocysteine (Hcy) concentrations, blood lipids, folic acid and vitamin B12 levels of all the participants were measured at the beginning and end of the eight weeks of resistance training.
The analysis of the data indicated that the Hcy levels of the CEG after resistance training and receiving the creatine supplement (9.33±4.60) was significantly lower than that of baseline (12.66±5.89) measurements, F(1,18)=12.28, P=0.00. No significant differences were seen in the Hcy levels of the PEG (15.01±10.87) after 8 weeks of training and receiving a placebo (12.46±12.50), F(1,16)=4.65, P=0.05. Furthermore, there were no significant differences among groups in terms of Hcy levels, F(2,52)=1.72, P=0.19.
The present study suggests that as well as strength gain; creatine supplementation with resistance training may afford some protection against emerging cardiovascular risk factors.
These experiments provide evidence that creatine, an end product of contraction unique to muscle, is involved in the control of muscle-protein synthesis. Skeletal muscle cells formed both in vitro and in vivo synthesize myosin heavy chain faster when supplied creatine in vitro. The response is apparent within four hours after addition of creatine to the culture medium, and is dependent on concentration over a range of 10-100 muM creatine. The effect seems to be selective for cell-specific proteins(s), since the rate of total protein synthesis is unaffected.
Measuring muscle mass is an important component of the nutritional assessment examination and a suggested index of this body space is the 24-h urinary excretion of creatinine. The method originated from studies in a variety of animal species in whom early workers found a parallelism between total body creatine and urinary excretion of creatinine. Assuming that nearly all creatine was within muscle tissue, that muscle creatine content remained constant and that creatinine was excreted at a uniform rate, an obvious "corollary" was that urinary creatinine was proportional to muscle mass. The so-called "creatinine equivalence" (kg muscle mass/g urinary creatinine) ranged experimentally from 17 to 22. One of the limiting factors in firmly establishing this constant and its associated variability was (and is) the lack of another totally acceptable noninvasive technique of measuring muscle mass to which the creatinine method could (or would) be compared. An improved understanding of creatine metabolism and a variety of clinical studies in recent years has tended to support the general validity of this approach. However, specific conditions have also been established in which the method becomes either inaccurate or invalid. While creatinine excretion may serve as a useful approximation of muscle mass in carefully selected subjects, there remains a need for accurate and practical indices of muscle mass for use in the individuals in whom the method cannot be reliably applied.
1. A randomized, double-blind, placebo-controlled trial utilizing creatine as a potential lipid-lowering agent was conducted to determine plasma lipid, lipoprotein, glucose, urea nitrogen and creatinine profiles in men and women ranging in age from 32 to 70 years.
2. Thirty-four subjects (18 men and 16 women) with total cholesterol concentrations exceeding 200 mg/dl received either a creatine supplement (5 g of creatine plus 1 g of glucose) or a glucose placebo (6 g of glucose) for 56 days. Creatine and placebo were taken orally four times a day for 5 days and then twice a day for 51 days. Plasma analyses were measured at baseline, 4 and 8 weeks of treatment, and at 4 weeks after cessation of treatment (week 12).
3. Significant reductions in plasma total cholesterol, triacylglycerols and very-low-density lipoprotein-C occurred within the creatine monohydrate group. Minor reductions in plasma total cholesterol from baseline (233 ± 9 mg/dl) of 6% and 5% occurred at weeks 4 and 8, respectively, before returning to baseline at week 12. Baseline triacylglycerols (194 ± 21 mg/dl) and very-low-density lipoprotein-C (39 ± 4 mg/dl) were reduced by 23% and 22% at weeks 4 and 8, respectively, and remained attenuated by 26% at week 12. These results remained consistent when data were separated and analysed by gender. Finally, a small, but statistically significant increase in urea nitrogen was observed in women between baseline (11.8 ± 0.7 mg/dl) and week 8 (13.8 ± 0.7 mg/dl, P > 0.05). No significant differences were noted for low-density lipoprotein-C, high-density lipoprotein-C, total cholesterol/high-density lipoprotein ratio, glucose, creatinine, body mass, body mass index or physical activity within or between the experimental and placebo groups. However, a trend towards reduced blood glucose levels was present in males given creatine monohydrate (P = 0.051).
4. These preliminary data suggest that creatine monohydrate may modulate lipid metabolism in certain individuals. These observations may demonstrate practical efficacy to the hyperlipidaemic patient as well as providing possible new mechanistic insights into the cellular regulation of blood lipid concentrations.
To determine the effects of 28 d of creatine supplementation during training on body composition, strength, sprint performance, and hematological profiles.
In a double-blind and randomized manner, 25 NCAA division IA football players were matched-paired and assigned to supplement their diet for 28 d during resistance/agility training (8 h x wk[-1]) with a Phosphagen HP (Experimental and Applied Sciences, Golden, CO) placebo (P) containing 99 g x d(-1) of glucose, 3 g x d(-1) of taurine, 1.1 g x d(-1) of disodium phosphate, and 1.2 g x d(-1) of potassium phosphate (P) or Phosphagen HP containing the P with 15.75 g x d(-1) of HPCE pure creatine monohydrate (HP). Before and after supplementation, fasting blood samples were obtained; total body weight, total body water, and body composition were determined; subjects performed a maximal repetition test on the isotonic bench press, squat, and power clean; and subjects performed a cycle ergometer sprint test (12 x 6-s sprints with 30-s rest recovery).
Hematological parameters remained within normal clinical limits for active individuals with no side effects reported. Total body weight significantly increased (P < 0.05) in the HP group (P 0.85 +/- 2.2; HP 2.42 +/- 1.4 kg) while no differences were observed in the percentage of total body water. DEXA scanned body mass (P 0.77 +/- 1.8; HP 2.22 +/- 1.5 kg) and fat/bone-free mass (P 1.33 +/- 1.1; HP 2.43 +/- 1.4 kg) were significantly increased in the HP group. Gains in bench press lifting volume (P -5 +/- 134; HP 225 +/- 246 kg), the sum of bench press, squat, and power clean lifting volume (P 1,105 +/- 429; HP 1,558 +/- 645 kg), and total work performed during the first five 6-s sprints was significantly greater in the HP group.
The addition of creatine to the glucose/taurine/electrolyte supplement promoted greater gains in fat/bone-free mass, isotonic lifting volume, and sprint performance during intense resistance/agility training.
Oral creatine supplementation is widely used in sportsmen and women. Side effects have been postulated, but no thorough investigations have been conducted to support these assertions. It is important to know whether long-term oral creatine supplementation has any detrimental effects on kidney function in healthy population.
Creatinine, urea, and plasma albumin clearances have been determined in oral creatine consumers (10 months to 5 yr) and in a control group.
There were no statistical differences between the control group and the creatine consumer group for plasma contents and urine excretion rates for creatinine, urea, and albumin. Clearance of these compounds did not differ between the two groups. Thus, glomerular filtration rate, tubular reabsorption, and glomerular membrane permeability were normal in both groups.
Neither short-term, medium-term, nor long-term oral creatine supplements induce detrimental effects on the kidney of healthy individuals.
Elevated serum creatinine (SCr) levels are a predictor of end-stage renal disease, but little is known about the prevalence of elevated SCr levels and their correlates in the community.
In this cross-sectional, community-based sample, SCr levels were measured in 6233 adults (mean age, 54 years; 54% women) who composed the "broad sample" of this investigation. A subset, consisting of 3241 individuals who were free of known renal disease, cardiovascular disease, hypertension, and diabetes, constituted the healthy reference sample. In this latter sample, sex-specific 95th percentiles for SCr levels (men, 136 micromol/L [1.5 mg/dL]; women, 120 micromol/L [1.4 mg/dL]) were labeled cutpoints. These cutpoints were applied to the broad sample in a logistic regression model to identify prevalence and correlates of elevated SCr levels.
The prevalence of elevated SCr levels was 8.9% in men and 8.0% in women. Logistic regression in men identified age, treatment for hypertension (odds ratio [OR], 1.75; 95% confidence interval [CI], 1.27-2.42), and body mass index (OR, 1.08; 95% CI, 1.01-1.15) as correlates of elevated SCr levels. Additionally, men with diabetes who were receiving antihypertensive medication were more likely to have raised SCr values (OR, 2.94; 95% CI, 1.60-5.39). In women, age, use of cardiac medications (OR, 1.58; 95% CI, 1.10-2.96), and treatment for hypertension (OR, 1.42; 95% CI, 1.07-1.87) were associated with elevated SCr levels.
Elevated SCr levels are common in the community and are strongly associated with older age, treatment for hypertension, and diabetes. Longitudinal studies are warranted to determine the clinical outcomes of individuals with elevated levels of SCr and to examine factors related to the progression of renal disease in the community.
The use of creatine (Cr) in its supplemental form, Cr monohydrate, has become rather widespread. The discovery that the Cr and phosphocreatine (PCr) content in human muscle can be increased by oral ingestion of supplemental Cr has led to numerous studies examining its benefits on exercise performance. Cr monohydrate supplementation appears to result in an increased ability to maintain power output during high-intensity exercise and increase the rate of PCr resynthesis during the recovery phase of intermittent high-intensity exercise. Subjects supplemented with Cr monohydrate demonstrate a reduction in the accumulation of plasma lactate, ammonia, and hypoxanthine, indicating an alteration in energy metabolism and an attenuation of ATP degradation. Thus, higher concentrations of Cr seem to enhance the muscle's ability to sustain the high ATP turnover rates encountered during strenuous exercise. Another potential benefit is an increase in body mass which results from the ingestion of Cr monohydrate; however, the composition of the weight gain remains undetermined. This article discusses the theoretical basis for Cr supplementation and reviews what is known about its effects on performance.
(C) 1996 National Strength and Conditioning Association
The use of creatine as an ergogenic aid for athletic performance is growing in popularity, despite limited scientific support for its efficacy. The purpose of this study was to determine the effect of creatine (Cr) monohydrate (CrM) and creatine phosphate (CrP) supplementation on strength, body composition, and blood pressure over a 6-week period. Thirty-five males (age range = 19-29 years) with at least 2 years of strength training experience were tested on three separate occasions (pretest, 3 weeks, 6 weeks). Strength tests performed were the one-repetition maximum (1-RM) bench press, 1-RM leg press, and maximal repetitions on the seated preacher bar curl with a fixed amount of weight. Subjects were divided into three groups matched for strength: placebo (Pl), CrM, and CrP. All subjects were provided a standardized strength training regimen and ingested a loading dosage of 20 g per day for the first 3 days of the study, followed by a maintenance dose of 10 g per day for the remainder of the 6-week supplementation period. Significant differences were noted between the Pl group and the two Cr groups for changes in lean body mass, body weight, and 1-RM bench press. These results suggest that oral Cr supplementation will result in greater strength and fat-free mass development. In addition, CrP may be as effective as CrM in achieving these desired outcomes.
(C) 1999 National Strength and Conditioning Association
Thirty-six (16 men, 20 women) collegiate track and field athletes (sprinter, jumpers, and throwers) were randomly divided into a placebo (P, n = 21) group and a creatine supplemented (C, n = 15) group. Six weeks of supplementation consisted of 0.30 g?kg-1?d-1 of creatine monohydrate (Crm) or a placebo. Subjects were involved in a preseason conditioning program that consisted of interval sprinting and multijoint, large-muscle-group weight-training movements programmed in a periodized manner. Pretesting (PRE) and posttesting (POS) consisted of a 7-site skinfold analysis, hydrostatic weighing, countermovement vertical jump, static vertical jump, and 5 +/- 10-second maximum cycle ergometer rides. Data were analyzed using G T analysis of variance. Significant interactions occurred for several variables. Creatine effected superior gains (percent change creatine vs. placebo) in countermovement vertical jump height (7.0 vs. 2.3%), countermovement vertical jump power index (6.8 vs. 3.1%), average cycle peak power (12.8 vs. 4.8%), cycle average power (10.8 vs. 3.1%), cycle total work (10.8 vs. 3.5%), cycle initial rate of power production (30.0 vs. 11.2%), and lean body mass. These results suggest that 6 weeks of Crm intake can favorably enhance vertical jump, power output, work capacity, and lean body mass in men and women collegiate track and field athletes following a periodized training program.
(C) 1999 National Strength and Conditioning Association
This study investigated the influence of oral creatine monohydrate supplementation on hormone responses to high-intensity resistance exercise in 13 healthy, normally active men. Subjects were randomly assigned in double-blind fashion to either a creatine or placebo group. Both groups performed bench press and jump squat exercise protocols before (T1) and after (T1) ingesting either 25 g creatine monohydrate or placebo per day for 7 days. Blood samples were obtained pre- and 5 min postexercise to determine serum lactate, testosterone, and cortisol concentrations. Creatine ingestion resulted in a significant (p < 0.05) increase in body mass but no changes in skinfold thickness. Serum lactate concentrations were significantly higher at 5 min postexercise in both groups compared to resting values. From T1 to T2 there were no significant differences in postexercise lactate concentration during both exercise protocols in the placebo group, but the creatine group had significantly higher lactate concentrations after the bench press and a trend toward lower concentrations during the jump squat at T2. There were significant increases in testosterone concentration postexercise after the jump squat, but not the bench press, for both groups; 5-min postexercise cortisol concentrations did not differ significantly from preexercise values for both groups for either protocol. Creatine supplementation may increase body mass; however, test-osterone and cortisol may not mediate this initial effect.
(C) 1997 National Strength and Conditioning Association
In a 10-year prospective study, we investigated the utility of the serum creatinine level in predicting the development of hypertension in Japanese adults, all of whom lived in a rural community. The study included 229 subjects, 91 men and 138 women aged 30 to 69 years, who were normotensive (systolic blood pressure 140 mm Hg or less and diastolic blood pressure 90 mm Hg or less) and had no prior history of antihypertensive treatment at baseline (1979 to 1980). Hypertension was defined as systolic blood pressure more than 140 mm Hg and diastolic blood pressure more than 90 mm Hg and starting antihypertensive medication. Stepwise proportional hazard analysis selected serum creatinine (P < .001) as an independent, significant predictor of hypertension together with systolic blood pressure (P < .001), age at entry (P < .001), body mass index (P = .008), and diastolic blood pressure (P = .011). The age- and sex-adjusted relative risk for subjects with a serum creatinine level of 1.2 mg/dL or higher compared with those with a level less than 1.1 mg/dL was 0.42 (95% confidence interval, 0.25 to 0.71). The mechanism of this association might relate to muscle mass and physical exercise or, possibly, to a primary renal abnormality. It appeared that the serum creatinine level may be useful in predicting future hypertension.
There is evidence that cellular hydration state is an important factor controlling cellular protein turnover; protein synthesis and protein degradation are affected in opposite directions by cell swelling and shrinking. An increase in cellular hydration (swelling) acts as an anabolic proliferative signal, whereas cell shrinkage is catabolic and antiproliferative. The cellular hydration state is mainly determined by the activity of ion and substrate transport systems in the plasma membrane. Hormones, substrates, and oxidative stress can change the cellular hydration state within minutes, thereby affecting protein turnover. We postulate that a decrease in cellular hydration in liver and skeletal muscle triggers the protein catabolic states that accompany various diseases.
The effect of dietary creatine and supplementation on skeletal muscle creatine accumulation and subsequent degradation and on urinary creatinine excretion was investigated in 31 male subjects who ingested creatine in different quantities over varying time periods. Muscle total creatine concentration increased by approximately 20% after 6 days of creatine supplementation at a rate of 20 g/day. This elevated concentration was maintained when supplementation was continued at a rate of 2 g/day for a further 30 days. In the absence of 2 g/day supplementation, total creatine concentration gradually declined, such that 30 days after the cessation of supplementation the concentration was no different from the presupplementation value. During this period, urinary creatinine excretion was correspondingly increased. A similar, but more gradual, 20% increase in muscle total creatine concentration was observed over a period of 28 days when supplementation was undertaken at a rate of 3 g/day. In conclusion, a rapid way to "creatine load" human skeletal muscle is to ingest 20 g of creatine for 6 days. This elevated tissue concentration can then be maintained by ingestion of 2 g/day thereafter. The ingestion of 3 g creatine/day is in the long term likely to be as effective at raising tissue levels as this higher dose.
This report describes the distribution of serum creatinine levels by sex, age, and ethnic group in a representative sample of the US population. Serum creatinine level was evaluated in the third National Health and Nutrition Examination Survey (NHANES III) in 18,723 participants aged 12 years and older who were examined between 1988 and 1994. Differences in mean serum creatinine levels were compared for subgroups defined by sex, age, and ethnicity (non-Hispanic white, non-Hispanic black, and Mexican-American). The mean serum creatinine value was 0.96 mg/dL for women in the United States and 1.16 mg/dL for men. Overall mean creatinine levels were highest in non-Hispanic blacks (women, 1.01 mg/dL; men, 1.25 mg/dL), lower in non-Hispanic whites (women, 0.97 mg/dL; men, 1.16 mg/dL), and lowest in Mexican-Americans (women, 0.86 mg/dL; men, 1.07 mg/dL). Mean serum creatinine levels increased with age among both men and women in all three ethnic groups, with total US mean levels ranging from 0.88 to 1.10 mg/dL in women and 1.00 to 1.29 mg/dL in men. The highest mean creatinine level was seen in non-Hispanic black men aged 60+ years. In the total US population, creatinine levels of 1.5 mg/dL or greater were seen in 9.74% of men and 1.78% of women. Overall, among the US noninstitutionalized population, 10.9 million people are estimated to have creatinine values of 1.5 mg/dL or greater, 3.0 million have values of 1.7 mg/dL or greater, and 0.8 million have serum creatinine levels of 2.0 mg/dL or greater. Mean serum creatinine values are higher in men, non-Hispanic blacks, and older persons and are lower in Mexican-Americans. In the absence of information on glomerular filtration rate (GFR) or lean body mass, it is not clear to what extent the variability by sex, ethnicity, and age reflects normal physiological differences rather than the presence of kidney disease. Until this information is known, the use of a single cutpoint to define elevated serum creatinine values may be misleading.
To critically review the current data concerning potential safety concerns of oral creatine supplementation.
Medline was searched using keywords to locate published works relating to creatine supplementation and adverse effects. Abstracts that specifically studied potential adverse effects of creatine were also utilized, as were human and animal studies of creatine metabolism in various organ systems.
Specific data from studies that investigated creatine's side effects and metabolism were grouped by organ system to better describe potential safety issues.
Creatine supplementation results in weight gain due to water retention, which may impede performance in mass-dependent activities such as running and swimming. Although short-term use (fewer than 28 days) at recommended does has not been shown to cause significant adverse effects, the studies on which this is based involved small numbers of subjects, and none of the studies provided a sample size calculation. Furthermore, despite the fact that creatine is normally found in cardiac muscle, brain, and testes, these areas remain essentially unstudied with respect to oral creatine supplementation. Future studies should include large randomized controlled trials evaluating the short and long term effects of oral creatine supplementation on the renal and hepatic systems, as well as the many other organ systems in which creatine plays a metabolic role.
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 monohydrate, 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 (T1) and after (T2) the 50 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.
Ten physically active, untrained, college-aged males (26.4 +/- 5. 8 years old) received creatine (CR, 5 g creatine monohydrate + 3 g dextrose) and placebo (PLA, 7 g dextrose) supplementation four times per day for 5 days in a double-blind, randomized, balanced, crossover design. Performance was assessed during maximal and three repeated submaximal bouts of isometric knee extension and handgrip exercise. CR supplementation significantly increased (p <.05) maximal isometric strength during knee extension but not during handgrip exercise. CR supplementation increased time to fatigue during each of the three bouts of submaximal knee extension and handgrip exercise when compared to the PLA trials. These findings suggest that CR supplementation can increase maximal strength and time to fatigue during isometric exercise. However, the improvements in maximal isometric strength following CR supplementation appear to be restricted to movements performed with a large muscle mass.
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