Dietary protein safety and resistance exercise: what do we really know?

Lonnie M. Lowery and Lorena Devia. Dietary protein safety and resistance exercise: what do we really know? J Int Soc Sports Nutr. 2009 Jan 12;6:3.

Abstract: Resistance trainers continue to receive mixed messages about the safety of purposely seeking ample dietary protein in their quest for stimulating protein synthesis, improving performance, or maintaining health. Despite protein's lay popularity and the routinely high intakes exhibited by strength athletes, liberal and purposeful protein consumption is often maligned by "experts". University textbooks, instructors, and various forms of literature from personal training groups and athletic organizations continue to use dissuasive language surrounding dietary protein. Due to the widely known health benefits of dietary protein and a growing body of evidence on its safety profile, this is unfortunate. In response, researchers have critiqued unfounded educational messages. As a recent summarizing example, the International Society of Sports Nutrition (ISSN) Position Stand: Protein and Exercise reviewed general literature on renal and bone health. The concluding remark that "Concerns that protein intake within this range [1.4 – 2.0 g/kg body weight per day] is unhealthy are unfounded in healthy, exercising individuals." was based largely upon data from non-athletes due to "a lack of scientific evidence". Future studies were deemed necessary. This assessment is not unique in the scientific literature. Investigators continue to cite controversy, debate, and the lack of direct evidence that allows it. This review discusses the few existing safety studies done specific to athletes and calls for protein research specific to resistance trainers. Population-specific, long term data will be necessary for effective education in dietetics textbooks and from sports governing bodies.



While reading along with this review article it occurred to me just how unsure scientists in Ex Sci are of just how important protein intake is to athletes (particularly strength athletes). These studies that have been conducted are mostly on sedentary individuals which has its place of course however it is very hard to generalize and assume that everyone's body (trained or untrained) will synthesise excess protein similarly. This review also mentions ISSN's position on protein consumption and how it is unfounded as to how much protein is necessary for athletes and just exactly how much is too much. Many claims are made you can see them in all types of media without scientific support. If excessive protein intake is so dangerous than why isn't the number of bodybuilders/powerlifters death's due to renal disease or suffering from osteoporosis (since excessive protein consumtion is believed to create bone catabolism) at a preamature age? Also, is it possible that maybe its not just excessive protein consumption but perhaps it also deals with the "type" of protein consumed that have the so called detrimental effects on the body? Even though there aren't many studies that show excess protein is good or bad for athletes. According to Wolff's Law: The body will conform and adapt to the directions and stresses it is habitually exposed to. Now this law may apply to bone specifically, however, it is my thought that your body is always in survival mode. Therefore, any stress you put your body through habitually it will try to adapt and find better ways accomodate this contiuous stress. Also, I heard this from someone somewhere, if you overload your system with protein won't you force yourself into gluconeogenisis in which your body will begin using the excess protein (amino acids) for energy? I'm not sure, anyone got a response?

Abstract:Examination of a pre-exercise, high energy supplement on exercise performance

Background
The purpose of this study was to examine the effect of a pre-exercise high energy drink on reaction time and anaerobic power in competitive strength/power athletes. In addition, the effect of the pre-exercise drink on subjective feelings of energy, fatigue, alertness and focus was also explored.
Methods
Twelve male strength/power athletes (21.1 ± 1.3 y; 179.8 ± 7.1 cm; 88.6 ± 12.1 kg; 17.6 ± 3.3% body fat) underwent two testing sessions administered in a randomized and double-blind fashion. During each session, subjects reported to the Human Performance Laboratory and were provided with either 120 ml of a high energy drink (SUP), commercially marketed as Redline Extreme® or 120 ml of a placebo (PL) that was similar in taste and appearance but contained no active ingredients. Following consumption of the supplement or placebo subjects rested quietly for 10-minutes prior to completing a survey and commencing exercise. The survey consisted of 4 questions asking each subject to describe their feelings of energy, fatigue, alertness and focus for that moment. Following the completion of the questionnaire subjects performed a 2-minute quickness and reaction test on the Makoto testing device (Makoto USA, Centennial CO) and a 20-second Wingate Anaerobic Power test. Following a 10-minute rest subjects repeated the testing sequence and after a similar rest period a third and final testing sequence was performed. The Makoto testing device consisted of subjects reacting to both a visual and auditory stimulus and striking one out of 30 potential targets on three towers.
Results
Significant difference in reaction performance was seen between SUP and PL in both average number of targets struck (55.8 ± 7.4 versus 51.9 ± 7.4, respectively) and percent of targets struck (71.9 ± 10.5% versus 66.8 ± 10.9%, respectively). No significant differences between trials were seen in any anaerobic power measure. Subjective feelings of energy (3.5 ± 0.5 versus 3.1 ± 0.5) and focus (3.8 ± 0.5 versus 3.3 ± 0.7) were significantly higher during SUP compared to PL, respectively. In addition, a trend towards an increase in average alertness (p = 0.06) was seen in SUP compared to P.
Conclusion
Results indicate a significant increase in reaction performance, with no effect on anaerobic power performance. In addition, ingestion of this supplement significantly improves subjective feelings of focus and energy in male strength/power athletes.

My take:
I always see Redline products being marketed as a weight management supplement. It was good to see a study that tested reaction time, anaerobic power, and alertness after ingesting Redline. Unfortunately for myself, and a great percentage of the individuals that work out at the same gym, Redline extreme doesn't seem to offer any added benefit towards anaerobic power. One positive result people can take from this study, is on those days where you are physically and mentally fatigued Redline extreme may offer a solution to your alertness and reaction times to help power through your workout.
One problem I had with the design is 10 minutes after ingestion the subjects completed a four question survey then began their physical tests. The authors did not make it clear how long the survey took, but I am assuming four questions did not take too long. So overall each trial may have taken 45 minutes to an hour max to complete (if my math is correct) and I was under the impression that caffeine and other stimulants can take 15-45 minutes to start "kicking in." A possible future study could take that into account.

Meltdown: Thermogenic Effect of an acute ingestion of a weight loss supplement.

Abstract
The purpose of this study was to examine the acute effects of a weight loss supplement on resting oxygen uptake (VO2), respiratory quotient (RQ), caloric expenditure (kcal), heart rate (HR), and blood pressure (BP) in healthy and physically active individuals.
Methods
Ten subjects (5 male, 5 female; 20.2 ± 1.2 y; 172.2 ± 8.9 cm; 71.5 ± 17.2 kg; 17.3 ± 2.6% body fat) underwent two testing sessions administered in a randomized and double-blind fashion. During each session, subjects reported to the Human Performance Laboratory after at least 3-h post-absorptive state and were provided either 3 capsules of the weight loss supplement (SUP), commercially marketed as Meltdown® or 3 capsules of a placebo (P). Subjects then rested in a semi-recumbent position for three hours. VO2 and HR were determined every 5 min during the first 30 min and every 10 min during the next 150 min. BP was determined every 15 min during the first 30 min and every 30 min thereafter. The profile of mood states was assessed every 30 min.
Results
Area under the curve analysis revealed a significant 28.9% difference in VO2 between SUP and P for the three hour study period. In addition, a significant difference in energy expenditure was also seen between SUP (1.28 ± 0.33 kcal·min-1) and P (1.00 ± 0.32 kcal·min-1). A trend (p = 0.06) towards a greater utilization of stored fat as an energy source was also demonstrated (0.78 ± 0.23 kcal·min-1 and 0.50 ± 0.38 kcal·min-1 in P and SUP, respectively). Significant elevations in HR were seen during hours two and three of the study, and significantly higher average systolic BP was observed between SUP (118.0 ± 7.3 mmHg) and P (111.4 ± 8.2 mmHg). No significant differences were seen in diastolic blood pressure at any time point. Significant increases in tension and confusion were seen in SUP.
Conclusion
Results indicate a significant increase in energy expenditure in young, healthy individuals following an acute ingestion of a weight loss supplement. In addition, ingestion of this supplement appears to modify mood and elevate HR and systolic BP following ingestion
Reference
Thermogenic effect of an acute ingestion of a weight loss supplement
Jay R Hoffman , Jie Kang , Nicholas A Ratamess , Stefanie L Rashti , Christopher P Tranchina and Avery D Faigenbaum
Department of Health and Exercise Science, The College of New Jersey, PO Box 7718, Ewing, New Jersey 08628, USA

My take on it?
I had always thought that Ephedra was a nifty weight loss supplement so I wondered how long it would be before someone tried to do an end run around the FDA ban on it.
The supplement studied here (Meltdown) contains synephrine, which certainly sounds like it is related to ephedrine . . . but the authors don't make that clear.
Whilst more studies will no doubt be done on this one, I think the side effects of increased anxiety and confusion may be problematic, not to mention the increased Systolic BP. Additionally there seems to be an increase in vasoconstriction (hence the increased SBP), that could be problematic if this supplement were used in conjunction with exercise in the heat.

Abstract: Hydroxycut hepatotoxicity: A case series and review of liver

Abstract:

Dietary supplements represent an increasingly common
source of drug-induced liver injury. Hydroxycut is
a popular weight loss supplement which has previously
been linked to hepatotoxicity, although the individual
chemical components underlying liver injury remain
poorly understood. We report two cases of acute
hepatitis in the setting of Hydroxycut exposure and
describe possible mechanisms of liver injury. We also
comprehensively review and summarize the existing
literature on commonly used weight loss supplements,
and their individual components which have demonstrated
potential for liver toxicity. An increased effort to
screen for and educate patients and physicians about
supplement-associated hepatotoxicity is warranted.

Reference

Dara, L., Hewett, J., & Lim, J.K. (2008). Hydroxycut hepatotoxicity: A case series and review of liver. World Journal of Gastroenterology, 14(45), 6999-7004.

My Take

First of all, here are definitions that will be helpful...
hepatotoxicity- The quality or condition of being toxic or destructive to the liver.
hepatitis- inflammation of the liver, caused by a virus or a toxin and characterized by jaundice, liver enlargement, and fever.

The authors are trying to associate liver problems with consuming hydroxycut, but I don't think you can make this causal conclusion because N=2, and this is just a case study rather than an experiment. Instead hydroxycut is correlated with liver problems, but as mentioned in the paper, we are not sure why. On the other hand, the paper does an okay job at listing and briefly explaining the ingredients (Garcinia Cambogia, Chromium, and Camelia Sinensis) that may cause damage to the liver.

Effect of Capsaicin on Endurance in rats

Effect of capsaicin on endurance in rats

Several studies have been conducted on the effect of capsaicin and endurance. Where many studies failed to prove an improvement in endurance capacity by consuming a high diet in capsaicin or a capsaicin supplement, a study conducted by Tae- Woong Who and Fukio Ohta in Japan showed positive results. The researcher tested 49 male rates on endurance capacity. The rats where divided into 4 groups, a placebo group who didn’t receive a capsaicin treatment, and three groups where every group received either 6mg, 10mg or 15mg Capsaicin per kg body weight. The researchers tested half of the rats on their swimming endurance, where endurance was measured as time to exhaustion. The other half of the rats was just tested on blood values during a resting phase. The dose of 15mg/kg increased significantly endurance performance in rats. They also found out that Capsaicin intake had no influence on muscle glycogen in the resting rats but it influenced positively the glycogen content of the rats at exhaustion. The researchers concluded that the former tests which had failed to prove an improvement in endurance capacity with the supplementation of capsaicin wasn’t performed with a high enough dose.

I haven’t found a study on the effect of capsaicin and endurance performance on humans yet. But capsaicin has been proved to release pain and inflammation and has therefore become an increasing influence in treatment of several diseases like arthritis and is part of several ointments.

Wouldn’t it be great if capsaicin does not only relieve pain but through its antioxidant capacity improves endurance performance? I did the math of how much Capsaicin a human being would need to get the positive effect:

An average person of 80kg would need to take 1200mg (15mg*80)of Capsaicin daily in order to have a positive effect.

After doing a little research I found the content of Capsaicin in Chili which is about 2%. This would mean a human would need to take in 60g of Chili every day. This amount is not achievable. Supplementation would be needed. It would be interesting to see if Capsaicin really has the ability to improve endurance performance and in which dose a human would benefit of it. Further studies need to be conducted in order to reveal the truth about Capsaicin and the effect on endurance in humans. But next time, if a Mexican passes you in a 5k, you should think about the possible effect of Capsaicin.

Effects of exercise training and antioxidant R-ALA on glucose transport in insulin-sensitive rat skeletal muscle.

Saengsirisuwan V, Perez FR, Kinnick TR, Henriksen EJ.

Muscle Metabolism Laboratory, Department of Physiology, University of Arizona, College of Medicine, Tucson, Arizona 85721-0093, USA.

We have recently demonstrated (Saengsirisuwan V, Kinnick TR, Schmit MB, and Henriksen EJ, J Appl Physiol 91: 145-153, 2001) that exercise training (ET) and the antioxidant R-(+)-alpha-lipoic acid (R-ALA) interact in an additive fashion to improve insulin action in insulin-resistant obese Zucker (fa/fa) rats. The purpose of the present study was to assess the interactions of ET and R-ALA on insulin action and oxidative stress in a model of normal insulin sensitivity, the lean Zucker (fa/-) rat. For 6 wk, animals either remained sedentary, received R-ALA (30 mg. kg body wt(-1). day(-1)), performed ET (treadmill running), or underwent both R-ALA treatment and ET. ET alone or in combination with R-ALA significantly increased peak oxygen consumption (28-31%) and maximum run time (52-63%). During an oral glucose tolerance test, ET alone or in combination with R-ALA resulted in a significant lowering of the glucose response (17-36%) at 15 min relative to R-ALA alone and of the insulin response (19-36%) at 15 min compared with sedentary controls. Insulin-mediated glucose transport activity was increased by ET alone in isolated epitrochlearis (30%) and soleus (50%) muscles, and this was associated with increased GLUT-4 protein levels. Insulin action was not improved by R-ALA alone, and ET-associated improvements in these variables were not further enhanced with combined ET and R-ALA. Although ET and R-ALA caused reductions in soleus protein carbonyls (an index of oxidative stress), these alterations were not significantly correlated with insulin-mediated soleus glucose transport. These results indicate that the beneficial interactive effects of ET and R-ALA on skeletal muscle insulin action observed previously in insulin-resistant obese Zucker rats are not apparent in insulin-sensitive lean Zucker rats.

POST BY: Kevin Jones

Comments: First off, I'm not sure if I am doing this correctly. Please let me know if this is OK. Second, I wanted to post an article about ALA but I could not find any relevant studies on humans and glucose uptake. All I could find was studies on rats...

But after reading a few of these reports on ALA, it makes me wonder if I am just wasting my time and money on ALA supplements. From what I've gathered, ALA is only effective in insulin resistant obese individuals. I was under the impression that ALA mimicked insulin and helped increase glucose uptake, therefore increasing glycogen stores. But I am neither diabetic nor obese, so does the ALA do anything at all for me? I also believed that it is a powerful free radical scavenger and would be smart to use after exercise as an anti-oxidant to protect against all the metabolic by-products created during the workout.

FTC Proposes Revisions To Guidelines for Advertising Endorsements

The Federal Trade Commission ("FTC") has requested comment on amendments to its Guides Concerning the Use of Endorsements and Testimonials in Advertising ("Guides"). These Guides govern the use of consumer and expert endorsements and testimonials in advertising — including viral advertising occurring through blogs and other Internet-based endorsement programs. Although the Guides are not binding, they explain how the FTC interprets Section 5 of the FTC Act’s prohibition on unfair or deceptive acts or practices. Consequently, the FTC could bring a Section 5 enforcement action based on practices that are inconsistent with the Guides.

As background, the FTC has not changed its Guides since they were released in 1980. In January 2007, the Commission released two studies it had commissioned on testimonials and issued a broad invitation for comments on the continued importance and appropriateness of the Guides. Twenty-two comments were submitted. Based on this feedback, the Commission is now proposing extensive revisions to the 1980 Guides. The changes to the Guides include:

declaring that both advertisers and endorsers are legally responsible for false or unsubstantiated statements made in endorsements, or failing to disclose material relationships;
eliminating the safe harbor formerly provided by "results not typical" language in consumer testimonials;
expanding the obligation of experts and celebrities to disclose certain contractual relationships (for instance, when speaking on talk shows); and
suggesting potentially sweeping liability for advertisers who encourage blogging about and viral marketing of their products.

JISSN Announces New Editors-in-Chief

The JISSN announces that Jose Antonio, Ph.D. and Douglas Kalman, R.D., Ph.D. will take over the helm of Editor in Chief for the Journal of the International Society of Sports Nutrition. Under the previous leadership of Dr. Richard Kreider, of Texas A & M, the JISSN has grown to be the leading source of scientic information in the sports nutrition and supplements category. Click here to read the latest studies in the JISSN.

Milk Your Workout for all It’s Worth—5 Wheys Low-Fat Dairy is a Nutrient Powerhouse

Is your body getting what it needs after a workout? So many sports and health products are released every year; each one boasting superior benefits for workout recovery. Neon-colored drinks are posed as the best source of hydration, while formulations designed to emulate human milk are advertised as optimal muscle-building fuel, with little or no research to support the claims. If your blender is simply building clutter, and doing little for your muscles, look no further than cooler or your local grocer or convenience store for a convenient, effective post workout. Plain old non-fat or low-fat milk is a perfect post-workout recovery drink. So what are some traits of a good workout supplement?

1. Provides carbohydrates in the form of sugar

2. Good source of high quality protein, but is also low in fat

3. Protein content also has branched-chain amino acids

4. Contains liquid and electrolytes

5. Inexpensive and convenient

1. Provides carbohydrates in the form of sugar

After a workout, the body needs recovery food to completely benefit from the exercise. Carbohydrates are important after a workout for a few reasons. First of all, they help to maintain blood sugar, especially for people who are likely to experience hypoglycemic (low blood sugar) symptoms; Type 2 diabetics fall into this category. Also, sugar is a potent stimulator of insulin. Following a workout, insulin binds to recpetors on the muscle and sends a“signal” that it is time to make protein. An insulin spike right after a workout tells the genes for making muscle proteins to become activated.

Finally, sugar is a good source of carbohydrate for the quick replacement of glycogen stores. This is especially important for athletes (of any age and competition level) who will be playing in a tournament or several matches back to back. Athletes “hit the wall” when muscle glycogen is depleted; the sooner carbohydrate makes it to your muscles, the better. Skim milk contains the two-unit sugar lactose.

Also, sweetened low-fat milk products are also good to have after a workout. One study, conducted by Karp and his colleagues, compared low-fat chocolate milk to either a traditional hydration drink or another carbohydrate-containing beverage in between two hard endurance workouts. The athletes who got the chocolate milk were able to exercise longer in the second bout. In addition to chocolate milk, low-fat ice cream or low-fat yogurt are also good choices.

2. Good source of high quality protein, but is also low in fat

Once the muscles get the signal to increase protein synthesis, they need a steady stream of building blocks, or amino acids, to complete the process. Amino acids are obtained from protein in food. Milk is an especially good source of protein because it contains both quick-absorbing whey and slower-absorbing casein. Both of these protein types are shown to increase protein synthesis after a workout; however, some researchers think that the muscle-building benefits of each protein are maximized when the two are taken together. Unfortunately, many high quality protein sources are in solid form and also packaged with a lot of extra fat. Fat slows the rate at which food is emptied from the stomach into the small intestine, so having too much fat after a workout slows the adsorption of much-needed sugars and amino acids into the blood. This is why high-fat post-workout drink may not be a good choice. Low-fat dairy is one of the few natural, high-quality protein, low-fat post workout options.

3. Protein content also has branched-chain amino acids

Not all amino acids are created equal. Some cannot be made in the body and are considered “essential.” Branched-chain amino acids (BCAA) and the BCAA leucine, in particular, are special for a couple of reasons. First of all, the muscle prefers to use BCAA as fuel during a workout; the body will break down your own muscle mass to get them if your supply if insufficient, since all BCAA are essential amino acids. Also, the BCAA leucine, like insulin, tells the muscles to make more structural proteins, so leucine is both a nutrient and a “signal.” Low-fat milk is a great source of leucine; specifically, milk contains about 0.8g of leucine per 8oz (240mL) cup. Typically, sports nutrition experts recommend about 1.5-2 grams of leucine following a workout; therefore, 2 cups of fat-free milk would put you the ball park by providing 1.6 grams of muscle-building leucine.

4. Contains liquid and electrolytes

Until recently, it was assumed that the best post workout hydration source is an fruity electrolyte drink. However, a recent article published in the British Journal of Nutrition found that low-fat milk promotes hydration after exercise better than either commonly used sports drink or water.

5. Inexpensive and convenient

Last, but certainly not least, you shouldn’t have to go out of your way to give your body what it needs after a hard day and an even harder workout. Low-fat milk, ice cream and yogurts are everywhere! In summary, according to Karen Kafer, RD, National Dairy Council, “[Milk is a] nutrient-rich package…for athletes: protein, carbohydrates, fluid and electrolytes, and vitamins and minerals. The vitamin and mineral package in milk includes calcium, phosphorus, vitamin D, vitamin A, riboflavin, vitamin B12, niacin and potassium. Together these help with strong bones, convert energy to fuel working muscles and maintain fluid and mineral balance."

Jean offers nutrition coaching for weight loss, muscle gain, or any of your personal goals at her office in the Alico building in downtown Waco, TX. She also offers personal training services at Ironhorse gym on the corner of Franklin and 17th, which is also very convenient to downtown. Contact information can be found on her personal website.

BCAAs ameliorate fatigue due to sailing

Eur J Appl Physiol. 2008 Nov;104(5):787-94. Epub 2008 Aug 13. Effects of branched-chain amino acids supplementation on physiological and psychological performance during an offshore sailing race. Portier H, Chatard JC, Filaire E, Jaunet-Devienne MF, Robert A, Guezennec CY. AMAPP EA 4248, Université d'Orléans, 2 allée du château, Orléans, France. hugues.portier@univ-orleans.fr

The aim of the present study was to investigate the effect of protein diets, rich in branched chain amino acids (BCAA) on perceived exertion, mental and physical performance during an offshore sailing race that lasted 32 h. Twelve sailors were randomly allocated into one of two groups [Control (CON) and BCAA: n = 6/group]. The BCAA group consumed a standard diet of 11.2 MJ day(-1) (58% carbohydrate, 30% fat, 12% Protein) along with a high-protein supplement of 1.7 MJ day(-1) (40% carbohydrate, 35% protein, 25% fat) and 1.7 MJ day(-1) composed of 50% valine, 35% leucine, and 15% isoleucine. CON was given a standard diet of 14.5 MJ day(-1) (58% carbohydrate, 30% fat and 12% protein). During the race, heart rate was monitored. Subjects self-evaluated their feeling of fatigue every 3 h, and 12 samples of saliva from each subject were collected to perform cortisol assays. Before and after the race a vertical jump and a handgrip test were performed, and mental performance was evaluated with a standardized battery of tests. A significant increase in the feeling of fatigue was noted on the second day (D2) of race in both groups; the increase was higher in CON (P < 0.05). For both groups, salivary cortisol concentration followed a nycthemeral rhythm, with an alteration during the race as evidenced by high midnight cortisol levels between D1 and D2, and significantly decreased cortisol levels observed on D2 (P < 0.05). There was no change in physical performance at the end of the race in both groups. As a significant decrease (P < 0.05) in short-term memory performance was observed only in the CON group. These data indicate that an offshore sailing race enhances the feeling of fatigue, and decreases short-term memory performance. These detrimental consequences are reduced by a high-protein diet with BCAA.

Creatine has no harmful effects in football players

Br J Sports Med. 2008 Sep;42(9):731-5.
Creatine supplementation does not affect clinical health markers in football players. Cancela P, Ohanian C, Cuitiño E, Hackney AC. Lic. Biochemistry, Facultad de Ciencias, Universidad de la República, Uruguay. cohanian@netgate.com.uy

PURPOSE: To study the effects of 8-week creatine monohydrate (CrM) supplementation on blood and urinary clinical health markers in football players. METHODS: 14 football players were randomly assigned in a double-blinded fashion to Cre (n = 7) or Pla (n = 7) group. The Cre group ingested 15 g/day of CrM for 7 days and 3 g/day for the remaining 49 days, whereas the Pla group ingested maltodextrin following the same protocol. Football-specific training was performed during the study. Total body mass was determined and blood and urine samples were analysed for metabolic, hepatic, renal and muscular function markers, before and after supplementation. RESULTS: A gain of total body mass was observed after CrM intake, but not with placebo. Blood and urinary markers remained within normal reference values. There were no significant changes in renal and hepatic markers after CrM intake. However, total creatine kinase (CK) activity significantly increased, and uric acid level tended to decrease after CrM use. Likewise, serum glucose decreased in the Cre group following supplementation. No significant differences in urine parameters were found in either group after supplementation. CONCLUSIONS: 8 weeks of CrM supplementation had no negative effects on blood and urinary clinical health markers in football players. Properties of CrM may, however, be associated with an increase in CK activity, improving the efficiency for ATP resynthesis, a phenomenon indirectly confirmed by the decreasing tendency in uric acid concentration. Furthermore, CrM seems to slightly influence glucoregulation in trained subjects.