Greig Watson, PhD, and Douglas J. Casa, PhD, ATC, FACSM, contributed to conception and design; acquisition and evaluation and interpretation of the info; and drafting, vital revision, and closing approval of the article. Kelly A. Fiala, PhD, ATC; Amy M. Hile, MS; Melissa W. Roti, PhD; Julie C. Healey, MS; Lawrence E. Armstrong, PhD, FACSM; and Carl M. Maresh, PhD, FACSM, contributed to conception and design; acquisition and evaluation and interpretation of the info; and demanding revision and closing approval of the article.
Summary
Creatine monohydrate (CrM) loading (eg, 20 g·d−1 for five to 7 days) may cause muscle phosphocreatine content material to extend by as a lot as 50%,1–3 towards what seems to be an higher storage restrict of 160 mmol·kg−1 dry muscle.4 This elevated phosphocreatine content material supplies extra substrate for the phosphagen system and enhances its resynthesis price throughout intense muscular contraction.5 Consequently, maximal or close to maximal bursts of power and energy, anaerobic efficiency, and fast restoration between explosive train bouts may be improved.6–10 Not surprisingly, then, CrM use is very prevalent in staff sports activities similar to soccer, lacrosse, and ice hockey and by highschool,11–13 collegiate,14,15 skilled,16 and recreational17 athletes.
Issues have been raised about creatine use, nonetheless, due to anecdotal observations of elevated cramping, muscle damage, and warmth intolerance18 and strategies that it will increase the chance of dehydration through fluid shifts into the intracellular house.3,19 These issues are particularly related to train carried out in situations that restrict warmth dissipation, as a result of train efficiency and, extra importantly, particular person well being rely upon temperature regulation and hydration state.
Due to these issues, the American School of Sports activities Medication, in suggestions titled “The Physiological and Health Effects of Oral Creatine Supplementation,”20 said, “…there are concerns about the possibility of altered fluid balance, and impaired sweating and thermoregulation in athletes acutely loading with creatine in settings where there is potential for thermal stress.”20 Additional, “…high-dose creatine supplementation (ie, 20 g·d−1) should be avoided during periods of increased thermal stress, such as sports activities performed under high ambient temperature/humidity conditions.”20 Nonetheless, no scientific proof is offered to help this advice and, to our information, no research to this point help it.
Anecdotal claims of elevated incidence of cramps and damage weren’t supported by outcomes from a 3-year commentary of Nationwide Collegiate Athletic Affiliation Division IA school soccer gamers utilizing CrM throughout coaching and competitors.21 Furthermore, the 4 teams of authors22–25 who examined CrM use throughout train within the warmth reported that creatine use both didn’t alter22 or attenuated23–25 the thermal stress skilled by euhydrated people. Particularly, creatine resulted in decreased coronary heart price,24,26 a decreased rise in rectal temperature throughout train,24–26 and decreased metabolic price.24 Certainly, the osmotic property of creatine, which ends up in a concomitant inflow of water into the cell, will increase physique water23,24,26–28 via a mix of elevated extracellular fluid and intracellular fluid,23,24,26,29 and will have aided topics by delaying the development of dehydration.
Our goal was to look at the affect of creatine supplementation on warmth tolerance in dehydrated males throughout extended train interspersed with high-intensity bouts. This state of affairs is necessary due to the excessive incidence of creatine use amongst athletes who take part in demanding sports activities actions in which there’s potential for thermal stress and since dehydration accentuates the thermal and cardiovascular stress of train within the heat30 and is acknowledged as an intrinsic threat issue for warmth sickness.31,32 We hypothesized that creatine supplementation wouldn’t alter thermoregulatory, cardiorespiratory, metabolic, or perceptual responses.
METHODS
RESULTS
DISCUSSION – “does creatine dehydrate you”
Concern has been expressed about doable alterations in fluid steadiness and impairment of thermoregulation in athletes acutely loading with creatine in settings with the potential for thermal stress.20 To look at this, we in contrast thermoregulatory (rectal temperature, imply weighted pores and skin temperature, sweat loss), cardiopulmonary (V̇o2, minute air flow, respiratory change ratio, respiratory price, coronary heart price, blood strain), metabolic (plasma glucose, lactate), and perceptual responses (thirst, thermal sensation, scores of perceived exertion) in dehydrated males throughout 80 minutes of train (a typical size of time of a observe session or sport in quite a few sports activities) interspersed with high-intensity train bouts after per week of both CrM or placebo supplementation.
We discovered that CrM was related to higher upkeep of plasma quantity and barely greater (however regular) plasma glucose throughout train. Moreover, we discovered that urine osmolality and urine shade had been larger earlier than train and that urine particular gravity was greater earlier than and after train with CrM, indicative of elevated creatine and creatinine excretion throughout CrM. These urine information are necessary as a result of if urine particular gravity and/or urine shade (2 widespread hydration indices) are used to evaluate the hydration state of athletes supplementing with CrM, then these athletes could seem extra dehydrated or hypohydrated than they really are.
No distinction was famous within the ESQ scores earlier than and after train between CrM and placebo, suggesting that short-term creatine use was not related to any symptomatic negative effects. Of specific curiosity, the incidence of cramping was not elevated with CrM, in all probability as a result of there have been no abnormalities in plasma sodium and potassium, no distinction in dehydration stage incurred throughout train (CrM versus placebo), and no metabolic abnormalities, all of which have been offered as hypotheses to elucidate muscle cramping.44 Our information, subsequently, present that hydration state and thermoregulation weren’t adversely affected by short-term CrM supplementation in these males exercising within the warmth, nor did CrM enhance the incidence of signs of warmth sickness in contrast with placebo.
We discovered that 1 week of CrM supplementation elevated physique mass a median of 0.88 kg versus no change with placebo. That is according to earlier findings (+0.7 to 2.0 kg),22,24,27,45,46 though important will increase will not be at all times noticed after a 7-day loading part.27 The physique mass acquire possible concerned water retention, which happens as a consequence of the osmotic load of CrM, as evidenced by the considerably greater plasma osmolality with CrM versus placebo at relaxation earlier than dehydration (289 versus 283 mOsm·kg−1, P < 0.001) and through the EHT (296 versus 291 mOsm·kg−1, P = 0.028). Small will increase in contractile protein synthesis have been noticed after CrM supplementation,47 however the contribution to elevated physique mass is minimal in contrast with water retention, and the topics on this research weren't performing high-intensity exercise. Earlier researchers27 have proven that in creatine supplementation, retained fluid is distributed usually between the fluid compartments. In our research, then, it's possible that roughly two thirds of the physique mass acquire resulted from water retained within the intracellular fluid house and that the remaining third of the acquire was due to fluid retained within the extracellular fluid house. Consequently, plasma quantity could have elevated barely (∼50 mL) with CrM.48
Dehydration resulted in comparable losses of physique mass and plasma quantity for CrM and placebo. In the course of the preliminary 20 minutes of the EHT, nonetheless, plasma quantity was considerably lowered with placebo however not with CrM; each values decreased equally thereafter till the tip of train. This consequence contrasts with the findings of Volek et al,22 who noticed no distinction in share change of plasma quantity throughout 35 minutes of intense biking within the warmth. Our information recommend that creatine use could restrict the motion of fluid out of the plasma and into the intracellular fluid house on the onset of train within the warmth, when topics are dehydrated. Nonetheless, the upkeep of plasma quantity and the rise in complete physique water weren't related to a change in sweat loss or with decreases in rectal temperature, coronary heart price, blood strain, or perceptual responses (thirst, thermal sensation, and scores of perceived exertion) and, subsequently, CrM didn't present a measurable hydration or thermoregulatory benefit. It's unclear why plasma quantity was maintained with CrM, however extracellular quantity could have been maintained as a consequence of the osmotic property of creatine and elevated plasma osmolality. In settlement with earlier findings22,24 and as indicated by comparable physique mass losses for CrM and placebo, the general stage of dehydration attained by the tip of train was not affected by CrM. Consequently, athletes shouldn't be involved that creatine supplementation alone could contribute to whole-body dehydration whereas exercising for extended durations underneath important thermal stress. On this research, CrM supplementation had no impact on V̇o2, plasma lactate, or respiratory change ratio, which is in settlement with earlier analysis inspecting creatine use throughout train within the warmth.24 Contrasting outcomes for V̇o2 throughout submaximal train in a temperate setting have been noticed; nonetheless, as a result of V̇o2 both was unaltered49 or was attenuated (together with lactate accumulation),50 neither necessitate concern about CrM use. Our information help the suggestion of Kilduff et al24 that muscle bioenergetics are unaffected by creatine throughout train within the warmth, and ours are the primary information to indicate this in dehydrated males. At present, no proof exists to help an impartial and contrasting impact of CrM on minute air flow and respiratory price. Consequently, as there have been no interplay or remedy variations in V̇o2, plasma lactate, or respiratory change ratio, the contrasting interactions discovered for minute air flow (rising extra in placebo) and respiratory price (rising extra in CrM) are troublesome to elucidate. Each effect-size statistics (η2) for these interactions had been weak, nonetheless. The elevation of plasma glucose with CrM can be troublesome to elucidate. Nonetheless, proof means that creatine supplementation disrupts glucose homeostasis. For instance, Rooney et al51 confirmed elevated blood glucose in topics after they ingested a 75-g glucose load following creatine supplemention for 42 days. The modifications in plasma glucose had been impartial of modifications in plasma insulin, however a mechanism to elucidate the disruption in glucose homeostasis was not established. It's doable {that a} comparable disruption in glucose homeostasis resulted from the 46 g of carbohydrate contained within the meal eaten 90 minutes earlier than the EHT. In neither research, nonetheless, was plasma glucose ever abnormally excessive. We discovered no impact of CrM on train coronary heart price and blood strain responses, and to our information, these are the primary information to indicate these outcomes with the added part of reasonable dehydration. Earlier analysis reveals contrasting findings: creatine supplementation throughout train within the warmth both had no impact on coronary heart price and blood pressure22 or attenuated coronary heart price.24 Methodologic variations (length and depth) possible clarify these contrasting outcomes, however once more, trigger for concern about short-term CrM supplementation on this inhabitants was not supported. Physique temperature (rectal temperature and imply weighted pores and skin temperature), thermal sensation, and the Physiological Pressure Index (a criterion of warmth pressure)38 weren't altered by CrM supplementation. Earlier authors who've examined creatine use and train within the warmth have proven that physique temperature responses are just like placebo22 or that creatine attenuated the rise in physique temperature versus placebo.23–25 Our information prolong these findings and are the primary to point that creatine doesn't considerably have an effect on temperature regulation and cardiovascular responses in skilled, dehydrated males performing intense train underneath excessive thermal stress. General (ie, entire physique exertion), central (ie, exertion related to respiration) and decrease physique (ie, leg exertion) scores of perceived exertion weren't affected by short-term CrM supplementation. Kilduff et al,24 nonetheless, discovered that creatine supplementation considerably lowered scores of perceived leg fatigue throughout train and elevated the benefit of train after supplementation. In distinction to our research, Kilduff et al additionally discovered that creatine considerably decreased coronary heart price, rectal temperature, and sweat price to offer a mechanism for lowered warmth pressure and dehydration throughout train. Acute urine quantity was unaltered by CrM supplementation however urine osmolality was greater throughout CrM supplementation. Earlier investigators have reported increased22 and decreased3 24-hour urine volumes after per week of creatine loading. The CrM altered urine shade, urine particular gravity, and urine osmolality. These modifications had been possible due to will increase within the urinary content material of creatinine52 and creatine53 ensuing from creatine supplementation.CONCLUSIONS
Our information add to the rising variety of research exhibiting that short-term CrM supplementation doesn’t adversely have an effect on thermoregulatory, cardiorespiratory, metabolic, or perceptual responses in individuals exercising underneath thermal stress. Our research was the primary to indicate this in dehydrated people. Moreover, short-term CrM supplementation was not related to elevated incidence of damaging negative effects (ie, cramping or warmth diseases and accidents). Consequently, concern for skilled males who complement with creatine, a minimum of within the brief time period, and train underneath thermal stress stays unfounded. The final advice for individuals to not use creatine whereas exercising underneath thermal stress must be reconsidered.
Acknowledgments
“does creatine dehydrate you”