The past 4
posts on Diet/Nutrition have been
concerned with the MACRONUTRIENTS; Proteins, Carbohydrates and Fats. Since an adequate and well-balanced diet
will likely provide MICRONUTRIENTS (vitamins and minerals) in sufficient quantities, THIS POST will focus
on SUPPLEMENTS.
The use of
dietary supplements by athletes is
overwhelmingly widespread in sports. Sports Supplements have become a
powerful industry making billions of
dollars worldwide. However, the IAAF Nutrition in Sport (2007) Document warns
that athletes should NOT expect benefits
from MOST of these supplements.
In fact, the
reality is that many supplements can either
pose serious health risks or “positive drug” test results OR both, due to
ingesting larger than recommended doses OR banned
ingredients that ARE NOT LISTED as ingredients on the labels.
The vast
majority of these types of supplements are marketed with claims that they can reduce body fat levels, build bigger AND
stronger muscles FASTER and/or improve performance. These are the supplements
that contain ingredients that are either on the banned list and can lead to
positive drug tests OR contain ingredients that can lead to serious health
risks. In many cases, these types of
ingredients CAN CAUSE BOTH health risk and positive drug test results.
Let me begin my recommendations regarding
SUPPLEMENTS that may be of benefit with this statement:
“SUPPLEMENTS
DO NOT COMPENSATE FOR POOR FOOD CHOICES AND INADEQUATE AMOUNTS OF NUTRIENTS AS
A RESULT OF POOR EATING HABITS!”
As I
mentioned in the recent post on Protein Powders, Protein supplements, protein
bars and amino acid preparations are among the most hyped, marketed and
purchased sports nutrition products.
As also suggested in that post, athletes can easily attain adequate protein for
muscle growth and repair from a well balanced diet that contains meat, fish,
eggs, etc. and extra protein is seldom required beyond a serving or two of a protein powder that contains a mix of
milk, egg, whey proteins WHEN dietary intake DOES fall short.
It should
also be made clear that whole proteins found in foods generally have advantages over individual amino acids and amino acid preparations.
IN ADDITION,
compounds with muscle building claims such as chromium, born, HMB (hydroxymethylbutyrate), colostrum, etc. HAVE NOT
BEEN PROVEN to provide substantial benefits for athletes.
WHY
ATHLETES TAKE SUPPLEMENTS
Athletes
generally look to supplements to: 1)
promote adaptations to training, 2) increase energy supply, 3) allow for more
consistent/intensive training by promoting recovery between training, 4)
maintain good health TO REDUCE illness/fatigue that can interrupt training
AND/OR speed healing processes for injuries and 5) to enhance competitive
performance.
Some
supplements aimed at immune system
health, such as glutamine, zinc, Echinacea, colostrum, Goldenseal, etc. but
there has been NO strong or consistent evidence to support effectiveness of
these mineral/herb supplements. AS
REPORTED IN THE POST ON CARBOHYDRATES, sound
evidence exists that a high carb diet, in TANDEM WITH APPROPRIATE REST AND
SLEEP VOLUMES, CAN LOWER STRESS HORMONE LEVELS.
SUPPLEMENTS
THAT HAVE SHOWN BENEFITS FOR ATHLETES IN TRAINING
At this
time, creatine, caffeine and certain
buffering agents have been shown to improve performance in conjunction with
certain training methods/ modes. For instance, creatine has been shown to be of benefit to STRENGTH/POWER/SPEED or
ALACTIC training BUT is clearly not of benefit to ENDURANCE ATHLETES. Endurance
athletes, along with STRENGTH/POWER/SPEED athletes, CAN benefit from both caffeine and buffering agents for both
training and competition uses.
CAFFEINE
A small
amount of caffeine (1-3mg/kg body
wt.) can help performance in prolonged exercise (endurance activities) and may also be helpful in exercise of
shorter duration: ex:”a caffeine dose of
as little as 2mg/kg of body wt. has been shown to help improve REPEAT sprint
capabilities in some studies.” Many
studies regarding this BENEFIT FOR REPEAT EXPLOSIVE ACTIVITIES have put forth the theory that is may be a
benefit for “well-trained” athletes BUT limited in effect for less-fit
athletes.
Such small
amounts can be found in common sports drinks, energy drinks, coffee and cola
products (including gels). For example, 100mg of caffeine can be obtained from a 12 oz. coffee or 24 oz. cola drink.
LARGER doses of coffee ARE NOT MORE EFFECTIVE and CAN HAVE NEGATIVE
SIDE-EFFECTS ON SLEEP PATTERNS.
Those who do
not normally use caffeine products can
experience short-term effects such as ANXIETY and muscular twitching because
they are not acclimated to caffeine. IT SHOULD ALWAYS BE USED IN TRAINING ON A
TRIAL BASIS BEFORE USING CAFFEINE IN COMPETIONS.
BUFFERING
AGENTS
As noted in “GENERATING ANAEROBIC POWER, CHAPTER 14, by
Dr. David Martin (High Performance Training for Sports, Joyce
& Lewindon),”The two major peripheral limitations to HIGH INTENSITY
EXERCISE are likely energy supply (total
pool of ATP,adenosine triphosphate and creatine phosphate) and ability to buffer waste products of
anaerobic metabolism (accumulation of H+ or hydrogen atoms) which interferes
with muscle contraction and production of energy via anaerobic metabolic
pathways.”
As discussed
above and in the article following this post, creatine can improve skeletal muscles content of high-energy
phosphates .
Many other studies have demonstrated that many buffering agents (sodium bicarbonate, sodium citrate and
sodium-phosphate) can be used to
increase anaerobic capacity, These increases in anaerobic capacity lead
directly to the improvement of
high-intensity exercise and performance.
Sodium bicarbonate (baking soda), ingested 1-2 hours prior to
short, high intensity exercise (30-300 seconds) at a dose of 0.3 gms./kg body
wt. can provide performance/exercise benefits via improved anaerobic work capacity. Too large a dose, however, can cause severe
gastric-intestinal distress so use in training prior to use in competition is
HIGHLY RECOMMENDED.
Beta-alanine, in more recent studies has proven to act as a
nutrient AID to improve intracellular buffering capacity and, in certain
studies, improve maximum performances
lasting between 60-240 seconds. These improvements ARE MOST LIKELY due to
the enhancement quality that beta-alanine contributes to the enrichment of
intramuscular carnosine levels. Carnosine
is an important chemical in the maintenance of the acid-base balance with skeletal muscle.
SLEEP
Although not
listed as a supplement, SLEEP is
absolutely necessary to all YOUNG CHILDREN, Pre-Adolescent, Adolescent and
Adults!
SLEEP is the primary VEHICLE for PERFORMANCE ENHACEMENT of both physical and cognitive performances.
SLEEP is WHEN training adaptations, growth and maturation of body systems,
muscle- tendon tissue growth, repair and recovery from training stimulus TAKES
PLACE. Without adequate amounts of SLEEP, the young athlete may NOT experience
GROWTH POTENTIAL, POTENTIAL FOR SUCCESS IN ACADEMIC AND/OR ATHLETIC
PERFORMANCES.
In addition
to creatine, caffeine, sleep and
buffering agents, there are a number of FOODS that have been developed to
supply specific formulas of nutrients that supply energy in a form that is
quickly and easily digested and absorbed. These FOODS can be valuable to HELP
athletes meet energy requirements when everyday foods are not practical to eat
prior to training or competition. Examples include: sports gels, sports drinks,
sports bars that contain ONLY carbs, protein, fats, vitamins,
minerals/electrolytes in gel, solid or liquid forms.
CREATINE INFORMATION
At the
conclusion of my post I have included a THOROUGH, INFORMATIVE AND REPUTABLE
SOURCE of information on Creatine Supplementation. PART 1, on Theory behind supplementation may not be for most SO, please
scroll down to WHY, WHAT AND WHEN’s of proper methods of Creatine
Supplementation.
AS A TEASER, BELOW IS KEVIN’S FINAL PARAGRAPH:
So there you have it. Creatine supplementation is safe, effective, and cheap. Those three words are very hard to get in the same sentence when talking about a specific supplement, by the way. NOW, READ UP, UNDERSTAND AND APPLY!!!
Creatine and the Theory Behind Supplementation
Kevin Kuhn, M.S.Ed., CSCS
— 01 May 2012
“He that takes medicine and neglects diet wastes the skill of the physician.”
I just want to open this way because most supplements, like most medicines, are not as effective if the diet is poor. So if you have not yet read the Nutrition for the Power Athlete articles, I encourage you to do so.
The next thing I’d like to bring up before diving into the supplement world is…the bell shaped curve. If you have ever studied statistics, or even if you haven’t, you have most likely heard of it as it is the most prominent probability distribution used in statistics. Statistics was not my favorite class in undergraduate or graduate school, but I did learn many things that were/are practical and applicable to my life in general, but also my diet and training specifically. Without going into too much detail, and trying to keep things simple and relevant to our topic…the bell shape curve (sometimes called a normal curve) represents a normal distribution, and is an easy way to view how a specific variable or property has an “effect” on a group of people or population. Again, this is by no means a complete explanation of normal distribution, but it will serve our purposes. If you want to learn more, just watch a few videos on YouTube by searching “bell shape curve” or “normal distribution curve.” Or you can read a stats book…
Creatine and the bell curve: Works for
most, then a small percentage of non and super-responders!
Anyway, the basic premise is that an effect
of a specific variable will be distributed throughout a group in the shape of a
bell curve. This means, for example, that the response to a specific stimuli is
not exactly the same for every person in a group. If you think about it like a
spectrum, and using creatine as an example, the majority of a group will have
some significant response to creatine supplementation, while a small portion
will show a non-significant (non-responder) response and another small portion
on the opposite end of the spectrum will show a very significant response. If
you have ever seen the movie Unbreakable, (spoiler alert!) you’ll understand
how Mr. Glass and the main character are both the minority at opposite ends of
the human spectrum, with the majority of humans somewhere in between. Back to the point: even when research shows a supplement to be “effective”, there are, most often, “statistical outliers” that are either not dealt with statistically or are only mentioned in passing. Since creatine has been studied so heavily, we understand that the majority of people respond quite well to its use…while others seem to show little to no response at all. All that to say…if you try using it and it doesn’t seem to work, you may have poor quality creatine or you may just be a “non-responder”. As an example, Eric Cressey explains on his blog that he is a “non-responder” with regard to supplements, specifically mentioning that he does not gain “water-weight” often associated with creatine supplementation.
If you aren’t getting any stronger
using creatine, it’s not that it doesn’t work, you might just be a
non-responder, or need to buy less shady supplements!
Theoretical premise of Creatine
supplementation:The main theory behind the use of creatine comes down to turning ADP back into ATP. For most body cells, but specifically muscle cells, energy that is immediately available is stored in the form of a high-energy phosphate called ATP (adenosine triphosphate). Unfortunately (in my opinion) cells store only enough ATP to fuel max effort muscle contraction for a very limited time…like a few seconds. The process of generating fuel from ATP is called hydrolysis, because water is required for the reaction to occur. A very simplified version of how ATP serves as energy or fuel is as follows:
An enzyme, called ATPase separates one of the three phosphate bonds on ATP (adenosine triphosphate) which makes available energy for contraction, but also yields a proton, heat, entropy, and an inorganic phosphate. This reaction turns ATP into ADP (adenosine diphosphate) since the enzyme ATPase broke one the of the phosphate bonds.
So…
ATP + water (and the enzyme ATPase) = ADP + an inorganic phosphate + a hydrogen ion (proton) + heat + entropy + free energy.
A bit of an aside…but this is just another reason water is still the most important “ergogenic aid” out there. Without proper hydration, both this reaction to create energy as well as the ability to dissipate the heat created by this reaction could not occur. Dehydration = limited hydrolysis + over heating.
Water: Is it in you?
To maintain high intensity muscle
contraction, the body’s cells act to re-synthesize ATP from ADP and a high
energy phosphate. Creatine phosphate (CP, also called phosphocreatine, PCr),
which is also stored in very small quantities in muscle (enough for another
couple seconds of max effort muscle contraction), is a major player in the
reaction that turns ADP back into ATP so that the hydrolysis reaction can occur
to release more energy for contraction. So…
CP + ADP + a hydrogen ion (proton) = creatine + ATP + heat
So the theory is that ingesting creatine
monohydrate will increase cellular levels of CP, which would thenallow for more
immediate resynthesis of ADP and ATP and thus improve muscular strength and
endurance.
And what do you know? After 1000+
studies on creatine supplementation, the theory is quite sound and
supplementation quite safe. Though we now understand that creatine supplementation may have performance benefits for most (if not all) athletic activities, the potential benefits for the Power Athlete are quite clear. As I alluded to before, creatine supplementation increases the stored levels of CP (creatine phosphate) in the muscle. This means energy production for maximal effort activity can be maintained for longer than normal. Creatine supplementation may only allow for the maintenance of maximal sprint speed for a fraction of a second longer than normal, or the ability to complete 1 more rep when weight training, but when these gains are compounded over multiple training sessions, the results will speak for themselves.
Another way creatine can improve your athletic performance is by allowing more CP to be available for recovery between sets or bouts of a specific exercise or activity. For example, recovery between sets of squats or sprints can occur faster with creatine supplementation, allowing for a reduction in time between training sessions or an increase in the quality of each training session.
That’s all for now…but stay tuned for Creatine Part 2.
In the next article I’ll discuss the What, When, Why, and How of creatine supplementation, along with a few other details that research has brought to light on the topic.
Sources
Balsom, P.D., Soderlund, K., Edblom, B. (1994). Creatine in Humans with Special Reference to Creatine Supplementation. Sports Medicine. 18: 268-280.
Krieder, R.B. (2008). Sports Applications of Creatine. In J. Antonio, D. Kalman, J.R. Stout,M. Greenwood, D.S. Willoughby, and G.G. Haff (Eds.), Essentials of Sports Nutrition and Supplements (pp. 417-439). Totowa, New Jersey: Humana Press
Scott, C.B. (2008). Thermodynamics, Biochemistry, and Metabolism. In J. Antonio, D. Kalman, J.R. Stout, M. Greenwood, D.S. Willoughby, and G.G. Haff (Eds.), Essentials of Sports Nutrition and Supplements (pp. 3-20). Totowa, New Jersey: Humana Press
Creatine Part 2.
Now that the theory of supplementation is out of the way, we can dive into some specific questions. The Why, What, When, and How of creatine supplementation are rarely, if at all, addressed correctly and appropriately on a supplement label. Luckily for those of us who care about what we put into our pie-holes, research has answers to these questions.
The “Why” of supplementation:
So what are the benefits?
Well…even though brand new research shows that maximal effort activity may not be limited by how fast the body can resynthesize ATP, but by fatigue due to other neuromuscular mechanisms, creatine supplementation still improves performance. Did you catch that? We still don’t know exactly what causes maximal effort fatigue…but we do know creatine improves performance.
But it doesn’t just improve performance. It statistically and significantly improves performance. In fact, reviews of literature on creatine studies that measure exercise performance show the average gain in performance from supplementation to be around 10% to 15%. To break that down just a little, single effort sprint performance has been shown to improve by 1% to 5% and repeated sprint performance has been shown to improve by 5% to 15%. That could be the difference between a million dollar contract…and well, no contract. I’m just saying…
Back to reality.
We know the body only stores a limited amount of Creatine Phosphate and free creatine, which make up the creatine pool. A 150 lb. person stores about 120 grams in the creatine pool, two-thirds being CP and one-third being free creatine. To replenish used or depleted creatine and maintain the creatine pool, the body can do two things:
- Utilize creatine that is found in the diet
- Synthesize its own creatine from the amino acids glycine, arginine, and methionine.
Question:
If you could increase the total creatine pool, and thus the CP stored in muscle, would you?
Lets say, for example, that you are a
vegetarian. Research has shown that individuals maintaining a vegetarian diet
have lower than normal levels of stored CP. Now lets say that you have a
creatine synthesis deficiency and you can’t maintain a normal creatine pool.
Or, maybe you just want to increase your creatine pool above normal levels to maximize
athletic performance. Whatever the case may be, all are great reasons to
supplement with creatine.
Study after study on creatine monohydrate
supplementation have shown that the total creatine pool (about 120 grams) can
be increased up to 160 grams, though even slight increases in the creatine pool
have been correlated to improved performance measures. So the potential
benefits, summarized by the ISSN (International Society of Sports Nutrition)
are:- “increased muscle mass and strength”
- “increased single and repetitive sprint performance”
- “enhanced glycogen synthesis”
- “possible enhancement of aerobic capacity via greater shuttling of ATP from mitochondria and buffering of acidity”
- “increased work capacity”
- “enhanced recovery”
- “greater training tolerance”
To sum this portion up. Creatine supplementation improves performance. Bottom line.
The “What” of supplementation:
The “what” in this context deals with the specific type of creatine.
When it is all said and done, good old Creatine Monohydrate is still the best stuff out there. Though many, many, many supplement companies disagree with this statement (especially those selling creatine serum or creatine ethyl ester), no data to date has shown any other type of creatine to be any more effective at increasing creatine uptake than creatine monohydrate powder. In fact, some studies have even shown creatine serum to have no effect at all on muscle creatine uptake. Though many supplement companies have made claims that their type of creatine allows for greater muscle uptake, better absorption in the gut and blood stream, and less breakdown in the stomach, (when compared to creatine monohydrate) research has yet to show any of these to be true. So if you walk into GNC and pull all the creatine supplements off the shelves…the one that costs the cheapest (but is still pharmaceutical grade) is probably the one that works the best. Along those lines, the three main producers of creatine are labs in Germany, United States, and China. The United States International Trade Commission has collected data from independent lab testing, and places German and American creatine at the top of the list since more contaminants have been found in Chinese sources. If the product says it is pharmaceutical grade creatine monohydrate and is manufactured in a lab facility that is both continually inspected by a 3rd party and maintains either FDA or the respecting countries’ governmental guidelines, you probably have a solid product.
The “When” of supplementation:
Though many creatine product labels have a specific “time” for when you should take your creatine (immediately before training, 30 minutes before training, immediately upon waking, immediately after training, etc.), research shows that muscle uptake of creatine is directly related to insulin levels. For this reason, many protocols suggest ingestion of creatine with a meal. The increase in insulin levels due to ingestion of carbohydrates and protein or amino acids post training has been shown to increase protein synthesis and muscle glycogen “refueling.” So to get the most bang for your buck the ISSN explains: “Because insulin levels enhance creatine uptake, ingestion of creatine after exercise with a carbohydrate and/or protein supplement may be an effective way to increase and/or maintain muscle creatine stores.” So holding off to supplement until immediately after you train seems to be the best option.
Creatine Supplementation: Best done
immediately post-workout to help harness the power of insulin!
The “How” of supplementation:As far as the “how” part of supplementation goes, there are 3 main protocols.
The most commonly used protocol (Loading/Maintenance) in supplementation studies involves a “loading” phase (usually 5-7 days) in which creatine is ingested at .3g/kg/day. The total is usually spread out in smaller chunks throughout the day in 5-ish gram increments. So for a 150 lb. person:
.3 x (150/2.2) = about 20 grams/day or 5 grams of creatine monohydrate taken 4 times throughout the day.
After the “loading” phase of 5-7 days, muscle creatine levels are maintained by taking 3-5 grams of creatine monohydrate per day. This protocol is used most often since muscle creatine stores may reach full capacity (an increase of 10%-40%) after 2-3 days of supplementing.
Another protocol (Low-dose) involves supplementing 3 to 6 grams of creatine monohydrate per day. Though 3 grams per day for 28 days has been shown to fully “saturate” muscle creatine stores, it increases these stores in a slower and steady manner.
The third most common protocol (High-dose) involves supplementing .3g/kg/day during training. This is used least often since muscle creatine stores are maxed out within a few days and only a fraction of the dose is needed to keep muscle creatine levels at maximum. Save your money.
Some protocols also take advantage of cycling periods of creatine supplementation. Since it takes about 4 to 6 weeks for the elevated creatine store level to return the pre supplementation level, you don’t really have to take creatine everyday of training. This type of cycling is theorized to increase the naturally occurring level of muscle creatine over time, or at least maintain them. In contrast to cycling, some researchers are now suggesting treating creatine supplementation they way we treat nutrients (carbs, protein, fat, vitamins, minerals, etc.). In other words, taking a low dose (3-5 grams) every day (regardless of training status or periodization cycle) to maintain elevated muscle creatine stores…all the time. I have a strong feeling that this will be the “protocol” that most will follow in the near future.
These aren’t the only relevant questions…
You probably have a few other questions floating through your mind right now…so I’ll try to address those, too.
Does it work right away? Since you can max out your creatine stores within a few days (Loading protocols), research shows performance benefits even for short-term supplementation.
What about long term supplementation? Research shows that supplementing with creatine over extended periods of time (12 weeks or more) leads to greater strength and performance gains. Research also shows that long term supplementation is safe when used within the proper guidelines.
Side effects? The only significant side effect reported in the clinical studies is weight gain. All the anecdotally reported side effects (i.e., dehydration, cramping, muscle pulls/tears, etc.) have been refuted by research reviews and other studies looking into the medical safety of this supplement. Interesting thing to note is that creatine supplementation may actually help reduce the risk of heat related injuries due to the increase in muscle “water-weight” associated with supplementation.
One more thing to consider…
Before you decide whether or not creatine supplementation is for you, I have one more piece of information to share.
When it comes to training for power, muscle size is a pretty big deal. Increases in muscle size (hypertrophy) occur concurrently with increases in myonuclei. So what does that mean? Muscle fibers (cells) have one (but not the only) specific characteristic that differentiates them from most other cells in the body. They have more than one nucleus. The greater the number of nuclei within a cell means the greater potential for muscle protein synthesis, and thus more potential for training adaptation.
So how do you increase the number of nuclei in muscle? Let me introduce you, if you have not already been acquainted, to satellite cells.
Satellite cells are basically muscle “stem cells” that exist on the outer edges of skeletal muscle fibers. When a muscle fiber is damaged, especially the type of damage that occurs due to training, satellite cells are activated and then go through one or more of the stages of mitosis to form “daughter cells” in order to help repair the damaged muscle. These daughter cells can go through further stages of mitosis and become a myotube. A myotube can then “donate” its nucleus to existing muscle fibers, thus increasing the total number of nuclei within a muscle fiber…and thus increasing potential for muscle protein synthesis and advanced training adaptation. Pretty cool stuff. The coolest part, however, is this: Creatine supplementation in combination with resistance training has been shown to increase the number and activity of satellite cells as well as increase the number of myonuclei within muscle fibers more than resistance training alone.
So there you have it. Creatine supplementation is safe, effective, and cheap. Those three words are very hard to get in the same sentence when talking about a specific supplement, by the way.
- Creatine has a variety of proven benefits for speed/power athletes.
- Creatine is best taken directly after a workout with your post-workout supplement.
- American and German creatine monohydrate powders are the way to go; steer clear of the fancy liquid creatine supplements.
- It does not take long in the supplementation process to start noticing the effects of creatine.
- There are a variety of ways to take creatine, you don’t have to take it every single day, and cycling is a good idea when supplementing with it.
- Creatine works with satellite cells during supplementation and resistance training to pack greater amounts of myonuclei into muscle fibers.
United States International Trade Commission, Creatine Monohydrate from the People’s Republic of China: Investigation No. 731-TA-814 (Preliminary). Determination and Views of the Commission (USITC Publication No. 3177, April 1999). Retrieved from
Burke, D.G., Chilibeck, P.D., Parise G., Candow, C.D., Mahoney, D., and Tarnopolsky, M. (2003). Effect of Creatine and Weight Training on Muscle Creatine and Performance in Vegetarians. Medicine and Science in Sports and Exercise. 35: 1946-1955.
Hultman, E., Soderlund, K., Timmorns, J.A., Cederblad, G., and Greenhaff, P.L. (1996). Muscle Creatine Loading in Men. Journal of Applied Physiology. 81: 232-237.
Bundle, M.W. & Weyand, P.G. (2012). Sprint Exercise Performance: Does Metabolic Power Matter? Exercise & Sport Sciences Reviews. 40:3 174-182.
Krieder, R.B. (2008). Sports Applications of Creatine. In J. Antonio, D. Kalman, J.R. Stout,M. Greenwood, D.S. Willoughby, and G.G. Haff (Eds.), Essentials of Sports Nutrition and Supplements (pp. 417-439). Totowa, New Jersey: Humana Press
Chromiak, J.A. & Antonio, J. (2008). Skeletal Muscle Plasticity. In J. Antonio, D. Kalman, J.R. Stout,M. Greenwood, D.S. Willoughby, and G.G. Haff (Eds.), Essentials of Sports Nutrition and Supplements (pp. 21-52). Totowa, New Jersey: Humana Press
Olsen, S., Aagaard, P., Kadi, Fawzi, Tufekovic, G., Verney, J., Olesen, J.L., Suetta, C., and Kjaer, M. (2006). Creatine Supplementation Augements the Increase in Satellite Cell and Myonuclei Number in Human Skeletal Muscle Induced by Strength Training. Journal of Physiology. 573: 525-534.
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