In men with hypogonadism, a low level of testosterone is produced due to a problem in the testicles or the pituitary gland. According to Harvard Medical School, determining exactly what constitutes a low testosterone level is a controversial matter. Levels of this hormone fluctuate wildly and even vary according to the time of day. However, generally physicians only decide to treat a patient for hypogonadism if the blood testosterone level is below 300 ng/dL and the following symptoms outlined by The National Institutes of Health are present.    
Whey, the liquid remaining after milk has been curdled and strained, is rapidly digested and absorbed and has a remarkable ability to stimulate muscle protein synthesis (Hayes & Cribb, 2008). Whey is available in three varieties — whey protein powder, whey protein concentrate, whey protein isolate — and all provide high levels of the essential and branched chain amino acids, vitamins and minerals.
Most typical bodybuilding programs have way too many sets and reps and use the wrong exercises. However, if you lower the total volume, go heavier, and use compound movements as I’ve outlined above, there is nothing wrong with a body-part split for advanced lifters. In fact, it’s often less stressful to the joints than your average upper/lower split.
More specifically, you can expect to end up in the upper half of these ranges ONLY if you are a beginner, younger, and/or have amazing genetics. You can expect to end up in the lower half of these ranges if you are an intermediate or advanced trainee, older, and/or have poor genetics. The average person can expect to end up somewhere in the middle. Additional details here: How Much Muscle Can You Gain?

If you're a serious strength or physique athlete, you've surely heard that supplements can help you get the most from your intense training sessions and on-point diet. But which supplements? The market is overstuffed like a bodybuilder in a child's blazer! You might be tempted to wander through a digital forest of get-big blogs and personal guru websites, but unfortunately those places can often be rife with misinformation.


Despite the popularity of creatine among young people, there has been very little research conducted in children under age 18. Of those studies, a few have suggested a positive effect but the overall evidence is inconclusive. In one study, teenage swimmers performed better after taking creatine; in another study, it helped high school soccer players sprint, dribble, and jump more effectively.

Testosterone is a steroid from the androstane class containing a keto and hydroxyl groups at the three and seventeen positions respectively. It is biosynthesized in several steps from cholesterol and is converted in the liver to inactive metabolites.[5] It exerts its action through binding to and activation of the androgen receptor.[5] In humans and most other vertebrates, testosterone is secreted primarily by the testicles of males and, to a lesser extent, the ovaries of females. On average, in adult males, levels of testosterone are about 7 to 8 times as great as in adult females.[6] As the metabolism of testosterone in males is greater, the daily production is about 20 times greater in men.[7][8] Females are also more sensitive to the hormone.[9]
The bulking and cutting strategy is effective because there is a well-established link between muscle hypertrophy and being in a state of positive energy balance.[19] A sustained period of caloric surplus will allow the athlete to gain more fat-free mass than they could otherwise gain under eucaloric conditions. Some gain in fat mass is expected, which athletes seek to oxidize in a cutting period while maintaining as much lean mass as possible.
Put simply, "strength training means using resistance to create work for your muscles," says Hannah Davis, C.S.C.S. and author of Operation Bikini Body. So even if your mind jumps straight to those hardcore machines and massive weights, there are a lot of ways to create this resistance that require minimal equipment (or none at all). Bodyweight workouts can be an incredibly effective way to strength train. Squats and push-ups FTW. You can also use tools like dumbbells, medicine balls, TRX bands, resistance bands, kettlebells, and slider disks, to help get the job done, explains Davis. But if that sounds like gibberish don't worry about it. Keep it simple and focus on equipment-free routines first. No matter what you do, the most important thing is to find something that challenges you, says Davis.
Expert tip: “Optimum form and range of motion for the squat is very dependent on your physicality, structure, joint integrity, limb length, strength, flexibility, and current condition,” Reames says. Your range of motion is 90° max at the knee. Some guys will be able to go lower than this, but not everyone will squat to parallel, he says. And that’s totally okay. “Stick to form and the appropriate resistance levels for you; the squat is still one of the best and simplest moves for overall strength, building lower-body muscle, core strength, and athletic performance. 

Bodybuilding is the use of progressive resistance exercise to control and develop one's musculature for aesthetic purposes.[1] An individual who engages in this activity is referred to as a bodybuilder. In professional bodybuilding, bodybuilders appear in lineups and perform specified poses (and later individual posing routines) for a panel of judges who rank the competitors based on criteria such as symmetry, muscularity, and conditioning. Bodybuilders prepare for competitions through the elimination of nonessential body fat, enhanced at the last stage by a combination of intentional dehydration and carbohydrate loading, to achieve maximum muscular definition and vascularity, as well as tanning to accentuate the contrast of the skin under the spotlights. Bodybuilders may use anabolic steroids and other performance enhancing drugs to build muscles.

Most experts recommend starting with your larger muscle groups and then proceeding to the smaller ones. The most demanding exercises are those performed by your large muscle groups, and you will need your smaller muscles to get the most out of these exercises. But don't feel limited by that. You can do your exercises in any order you like, and changing the order is a great way to challenge yourself in different ways.
Present in much greater levels in men than women, testosterone initiates the development of the male internal and external reproductive organs during foetal development and is essential for the production of sperm in adult life. This hormone also signals the body to make new blood cells, ensures that muscles and bones stay strong during and after puberty and enhances libido both in men and women. Testosterone is linked to many of the changes seen in boys during puberty (including an increase in height, body and pubic hair growth, enlargement of the penis, testes and prostate gland, and changes in sexual and aggressive behaviour). It also regulates the secretion of luteinising hormone and follicle stimulating hormone. To effect these changes, testosterone is often converted into another androgen called dihydrotestosterone. 

Great Paleo beef protein, why? Because it doesn't have any preservatives, fillers, Dairy, soy, yeast, corn, or any other additives. No artificial colorings/flavorings. That makes this product not just paleo, but also autoimmune paleo friendly, hard to find. That basically means anti alergic, you dont get the same digestive issues many people get with whey. I think beef protein is underrated, I just finished a batch and went back to my whey. The whey gives me bloating/gas that this product doesnt. Also if you don't like how the amino acid profile stacks up agains Whey protein powder you can add some BCAA to powder, at least thats what I do. In a 30 gram saving you get 28 grams of protein (zero fat and zero carb), not bad!

Phosphocreatine is known to be a major source of energy for cardiac tissue alongside fatty acids, which are dominant under periods of normoxia (normal oxygen) while phosphocreatine becomes more important in periods of hypoxic stress.[281][282][283] The entire CK system plays a role in the recovery of the heart following ischemic/hypoxic stress, since blocking CK activity impairs recovery[284][285] and overexpressing CK activity promotes it.[286] This is due to the heart tissue needing high energy phosphate groups at this time, and the ischemic stress reduces CK activity and the ability of CK to donate these groups.[287][288]


If you’re exercising at your maximum intensity, your body literally can’t produce enough ATP to keep up. (10) That’s where creatine supplements come in: They can help increase your body’s stores of phosphocreatine (an organic compound of creatine and phosphoric acid that’s stored in your muscle tissue) to produce new ATP during high-intensity exercise.

This copyrighted, evidence-based medicine resource is provided by Natural Medicines Comprehensive Database Consumer Version. Natural Medicines Comprehensive Database disclaims any responsibility related to consequences of using any product. This monograph should not replace advice from a healthcare professional and should not be used for the diagnosis or treatment of any medical condition.
In females, this test can find the reason you’re missing periods, not having periods, or having a hard time getting pregnant. Doctors can also use it to diagnose polycystic ovary syndrome (PCOS). That’s a hormone problem that can cause irregular periods and make it hard to get pregnant. A testosterone test can also reveal if you might have a tumor in your ovaries that affects how much of the hormone your body produces.
How to do it: Stand with feet just outside the shoulders and hands behind your head. Squat, keeping your knees behind your toes and squeezing your glutes. After holding this position for two seconds, jump vertically. Pull the toes to your shins in midair to prepare for landing. Land in the starting squat position, hold three seconds and repeat for 10 reps. Be sure to land softly, with the hips back and down.
Testosterone may prove to be an effective treatment in female sexual arousal disorders,[52] and is available as a dermal patch. There is no FDA approved androgen preparation for the treatment of androgen insufficiency; however, it has been used off-label to treat low libido and sexual dysfunction in older women. Testosterone may be a treatment for postmenopausal women as long as they are effectively estrogenized.[52]
In addition to being potentially harmful, some have argued that there is little evidence to indicate any benefit to using bodybuilding protein or amino acid supplements. "In view of the lack of compelling evidence to the contrary, no additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise".[18] In dispute of this, one more recent meta-analysis concluded that for athletes participating in resistance exercise training and consuming protein supplements for an average of 13 weeks, total protein intake up to 1.6 g per kg body weight per day would result in an increase in strength and fat-free mass, i.e. muscle, but that higher intakes would not further contribute. The muscle mass increase was statistically significant but modest - averaging 0.3 for all trials and 1.0 to 2.0 kg, for protein intake ≥ 1.6 g/kg/day.[3]
It can be hard to know where to start when beginning strength training. There are countless exercises you can do, some of which work some muscles, but not others. There are safety concerns to beware of, a wide variety of sometimes confusing equipment to help you in your efforts, and so on. With some familiarity of the basics of getting started with strength training, actually doing so can become far less daunting, and you can begin to craft a routine that is targeted toward helping you achieve your personal goals.
Creatine is a molecule produced in the body. It stores high-energy phosphate groups in the form of phosphocreatine. Phosphocreatine releases energy to aid cellular function during stress. This effect causes strength increases after creatine supplementation, and can also benefit the brain, bones, muscles, and liver. Most of the benefits of creatine are a result of this mechanism.
When it comes to supplementation though, nitric oxide boosters still have a way to go. The body has a limit on how much L-arginine it absorbs. L-citrulline itself is converted to L-arginine in your body, and thus hits the rate limit again. Thus, neither supplement is reliable at increasing the concentration of nitric oxide in the blood. Agmatine is mostly untested on people, with no evidence for its muscle building effects. Manipulating nitric oxide levels may be a good way to build muscle, but the supplements currently on the market won’t help.
The last survivors of the pro-hormone supplements, which were removed from sale last January, estrogen-blocking supplements aren't pro-hormones but do inhibit the enzyme aromatase, which converts androgens into estrogens. In normal men that enzyme is ubiquitous, being present in such tissues as muscle, brain and skin. About 20 percent of the free testosterone circulating in the blood is converted into estrogen by way of aromatase.
In regard to carbohydrate oxidation during exercise, it appears that rats subject to intermittent physical exercise (which utilizes glycogen) have decreased lactate production during said exercise, suggesting a preservation of glycogen usage. This occurred alongside an increase in glycogen stores.[359] This is thought to be due to phosphocreatine donating phosphate to replenish ATP. Without any changes in whole body metabolic rate, it indirectly causes less glucose to be required to replenish ATP, due to a quota needing to be met during exercise and creatine phosphate taking up a relatively larger percentage of said quota.
D-aspartic acid can also help to reduce cortisol levels. Cortisol is known as the “stress” hormone because its production increases during stressful situations. High cortisol levels can have many negative side effects, such as weight gain, muscle tissue breakdown, or increased blood sugar. Taking a supplement that includes cortisol can reduce stress and prevent excess fat storage or muscle loss.
Perform the two workouts (Day 1 and 2) once each per week, resting at least a day between each. Perform the exercises marked with letters as a group. Do one set of A, rest, then one set of B, rest (note that some groups have an exercise “C”), and repeat until all sets are complete. Then go on to the next group. Perform three sets of 8–10 reps for each exercise. After a month, you’ll see how rewarding just a months in the gym can be.
It can be hard not to compare yourself to Schwarzenegger, with his action-star movie career, his stint as a president-appointed fitness ambassador and his election as governor of California. Chang said that Heath’s personality, including his charisma and outspokenness, is similar to that of Schwarzenegger, who is still omnipresent and beloved in the sport.

Creatine is stored in the body in the form of creatine and as creatine phosphate, otherwise known as phosphocreatine, which is the creatine molecule bound to a phosphate group.[39] Creatine phosphate is thought to maintain the ATP/ADP ratio by acting as a high-energy phosphate reservoir.[40] The more ATP a muscle has relative to ADP, the higher its contractility is, and thus its potential strength output in vivo.[41][42] This pro-energetic mechanism also affects nearly all body systems, not just skeletal muscle. [39] During periods of rest and anabolism, creatine can gain a phosphate group through the creatine-kinase enzyme pathway, up to a cellular concentration of 30uM[24] to be later used for quick ATP resupply, when needed.[43][44] 
People sometimes walk up and touch him, as if unsure if he is a man or a machine. What they do not realize is that beneath the stony exterior and self-assuredness is a squishy sense of anxiety and vulnerability. Heath gets nervous every time he strips to his posing trunks. He is rarely satisfied with what he sees in the mirror. He is persistently worried about imperfections others might find, too.
Different exercises will require different weights, but there are some markers that can help guide you towards the right resistance, whether you're using dumbbells, kettlebells, or a barbell. Go for a weight that feel heavy enough to challenge you, but not so heavy that you sacrifice your form. For example, if you're doing 15 reps, you should feel pretty fatigued by the time you hit rep 15. If you can breeze through all your reps, though, that's a sign you should up the weight.

How to do it: Lie on your back with your feet planted firmly on the floor, knees bent. If you’re just starting and using your bodyweight, reach your arms straight up over your chest and clasp your hands. If you’re using dumbbells, place the weight (plate, kettlebell, dumbbells) comfortably on your pelvis and hold it steady. To really activate your glutes, thrust your hips up toward the ceiling, driving with your legs, and dig your heels into the floor. Lower your hips until they’re hovering right above the floor level, then repeat.  
Carbohydrates play an important role for bodybuilders. They give the body energy to deal with the rigors of training and recovery. Carbohydrates also promote secretion of insulin, a hormone enabling cells to get the glucose they need. Insulin also carries amino acids into cells and promotes protein synthesis.[26] Insulin has steroid-like effects in terms of muscle gains.[27] It is impossible to promote protein synthesis without the existence of insulin, which means that without ingesting carbohydrates or protein—which also induces the release of insulin—it is impossible to add muscle mass.[28] Bodybuilders seek out low-glycemic polysaccharides and other slowly digesting carbohydrates, which release energy in a more stable fashion than high-glycemic sugars and starches. This is important as high-glycemic carbohydrates cause a sharp insulin response, which places the body in a state where it is likely to store additional food energy as fat. However, bodybuilders frequently do ingest some quickly digesting sugars (often in form of pure dextrose or maltodextrin) just before, during, and/or just after a workout. This may help to replenish glycogen stored within the muscle, and to stimulate muscle protein synthesis.[29]
There is a genetic condition known as gyrate atrophy of the choroid and retina, which is associated with a high level of Ornithine in the blood and a relative decrease in Arginine, which causes a relative creatine deficiency due to L-arginine being required to make creatine[478][479] and because high ornithine can suppress creatine synthesis (AGAT) in the glial cells of the retina.[475] This condition can be attenuated by either reducting ornithine in the diet[480] or by supplementing creatine, which is, in this instance, therapeutic.[481][482]
Muscle imbalances are quite common among strength athletes and are arguably the most common cause of their injuries. Many times this is due to a “weak link” in the kinetic chain of muscles that activate during their activity. Identifying the “weak” muscle and being able to feel, isolate and contract that “weak” muscle makes correctional exercise and rehab much easier. Bodybuilding training, with its focus on “feel” rather than movement, helps to train and develop the mind to muscle connection. This comes in handy when you need to train a muscle imbalance with correctional exercise and, in the case of injury, for rehab.
Drink plenty of water throughout the day, especially in the hours leading up to your workout. This can help you feel full and reduce hunger pangs. During training, drink about 8 ounces every 15-20 minutes, more when it's hot and humid. The reason is simple: Your performance quickly begins to suffer when the body is dehydrated just 1%-–2%. And if you wait till you feel thirsty, you've waited too long. A flavorful, low-calorie sports drink is a great way to hydrate. Try drinking fluids stored at cooler temperatures; studies show that people consume more when the liquid is colder.
In addition to the proper amount of sleep, do not overdo your training regimen. While you might be tempted to think that "more is better," in fact the opposite is true. You can reach a point known as "over-training", in which you'll lose the ability to "pump" (engorge the muscles with oxygen-rich blood) your muscles, and this can even lead to muscle wasting—exactly the opposite of what you are trying to achieve. Here are some symptoms to be aware of if you think you may be falling into the over-training zone:
Multivitamin supplements may help you reach the recommended daily intakes for vitamins and minerals if you have a less than ideal diet, travel impairs your diet, or strenuous exercise increases requirements. I consider a multivitamin good insurance in these circumstances against possible deficiencies. Choose a reputable brand. You should choose a good all-around supplement with a balanced formula.
In regard to the blood brain barrier (BBB), which is a tightly woven mesh of non-fenestrated microcapillary endothelial cells (MCECs) that prevents passive diffusion of many water-soluble or large compounds into the brain, creatine can be taken into the brain via the SLC6A8 transporter.[192] In contrast, the creatine precursor (guanidinoacetate, or GAA) only appears to enter this transporter during creatine deficiency.[192] More creatine is taken up than effluxed, and more GAA is effluxed rather than taken up, suggesting that creatine utilization in the brain from blood-borne sources[192] is the major source of neural creatine.[193][192] However, “capable of passage” differs from “unregulated passage” and creatine appears to have tightly regulated entry into the brain in vivo[193]. After injecting rats with a large dose of creatine, creatine levels increased and plateaued at 70uM above baseline levels. These baseline levels are about 10mM, so this equates to an 0.7% increase when superloaded.[193] These kinetics may be a reason for the relative lack of neural effects of creatine supplementation in creatine sufficient populations.
There is a genetic condition known as gyrate atrophy of the choroid and retina, which is associated with a high level of Ornithine in the blood and a relative decrease in Arginine, which causes a relative creatine deficiency due to L-arginine being required to make creatine[478][479] and because high ornithine can suppress creatine synthesis (AGAT) in the glial cells of the retina.[475] This condition can be attenuated by either reducting ornithine in the diet[480] or by supplementing creatine, which is, in this instance, therapeutic.[481][482]

The bones and the brain are two important tissues in humans where the primary effect of testosterone is by way of aromatization to estradiol. In the bones, estradiol accelerates ossification of cartilage into bone, leading to closure of the epiphyses and conclusion of growth. In the central nervous system, testosterone is aromatized to estradiol. Estradiol rather than testosterone serves as the most important feedback signal to the hypothalamus (especially affecting LH secretion).[119] In many mammals, prenatal or perinatal "masculinization" of the sexually dimorphic areas of the brain by estradiol derived from testosterone programs later male sexual behavior.[120]


First off, every single resistance-training athlete in the world should be very thankful for bodybuilding training. It was bodybuilding that brought weight training to the mainstream. The bottom line is that the average gym goer is MORE interested in how they look vs. how they perform. 99% of every client I ever trained had an aesthetic goal as their primary goal. In my 20 plus years as a trainer I can count maybe 10 clients who said, “My goal is to be able to bench press or squat or lift more weight.” It was the aesthetic focus of bodybuilding that opened the doors for all other resistance training pursuits to enter into the mainstream.
If you touch your phone between exercise sets, it better be to set its timer to 30 to 90 seconds. When lifting for hypertrophy, rest periods of 30 to 90 seconds encourage a quick release in muscle-building hormones (including testosterone and human growth hormone) while also making sure that you really, truly fatigue your muscles, according to Fitzgerald.
Nitrate-rich foods like beets, radishes, and pomegranates are a great way to boost the production of nitric oxide (NO). Although there's very limited research examining the effects of beet root juice and pomegranate extract on resistance training, these ingredients have previously been shown to increase skeletal muscle blood flow and lead to reduced soreness, which may ultimately lead to improvements in strength and performance.[9,10]
Creatine is a naturally occurring compound found in muscle in large amounts. Creatine monohydrate is the supplement form and combines is a combination of the amino acids arginine, glycine, and methionine. Creatine drives the important creatine phosphate energy pathway, which is important in high-intensity activity such as weightlifting. Creatine can improve body bulk and training performance in high-intensity activities. Be aware that not everyone responds to creatine supplementation and 30 percent of users may not see any improvement. Women may not benefit as much as men. In weight training, increased strength, bulk, and fat loss are reasonably consistent results.
A testicular action was linked to circulating blood fractions – now understood to be a family of androgenic hormones – in the early work on castration and testicular transplantation in fowl by Arnold Adolph Berthold (1803–1861).[182] Research on the action of testosterone received a brief boost in 1889, when the Harvard professor Charles-Édouard Brown-Séquard (1817–1894), then in Paris, self-injected subcutaneously a "rejuvenating elixir" consisting of an extract of dog and guinea pig testicle. He reported in The Lancet that his vigor and feeling of well-being were markedly restored but the effects were transient,[183] and Brown-Séquard's hopes for the compound were dashed. Suffering the ridicule of his colleagues, he abandoned his work on the mechanisms and effects of androgens in human beings.
These complete proteins include all of the essential amino acids that the body cannot produce itself. Different proteins, such as whey and casein, egg and soy have different absorption rates. Whether you should favor one over another for muscle building is still a subject of popular and scientific debate, although whey protein isolate, a more rapidly absorbed protein, has some support from various scientific studies. For protein powders, assess the value by checking out the protein listed on the label. Combined with resistance training, sufficient protein consumption along with an appropriate diet can lead to increased muscle and reduced body fat. You should read more about The Bodybuilding Diet for supplement timing issues before and after training. 
All you need to know about low creatinine levels Creatinine is a waste material in the body, and low levels can suggest a shortfall in liver function or activity. This MNT Knowledge Center feature looks at low creatinine levels., as well as information on what creatinine is, how it affects the body, and how to increase low creatinine levels. Read now
Three additional studies suggest that creatine supplementation may not be beneficial for running velocity, sprint swimming performance, or a maximal cycling effort [7]. Short bouts of repeated anaerobic activity have shown some potential benefits with creatine supplementation use in a laboratory setting. However, creatine supplementation has not been shown to enhance single-event performance such as stationary cycling [16-19]. Taken together, these studies do not support creatine supplementation to enhance aerobic activities such as distance running.
XPI's Myotein is a premium protein blend that features Casein, Whey Protein Isolate and Whey Protein Concentrate. That makes 25 grams of protein per serving of the most advanced protein formula, engineered for fast absorption and utilization. Each scoop also contains 2 grams fat and 2 grams carbs, and additional digestive enzymes for increased bio-availability. With several creamy flavors to choose from, Myotein is rated one of the best tasting protein powders on the market. Keep Reading »

A 2011 survey of 33 supplements commercially available in Italy found that over 50% of them exceeded the European Food Safety Authority recommendations in at least one contaminant. The most prevalent of these contaminants was creatinine, a breakdown product of creatine also produced by the body.[47] Creatinine was present in higher concentrations than the European Food Safety Authority recommendations in 44% of the samples. About 15% of the samples had detectable levels of dihydro-1,3,5-triazine or a high dicyandiamide concentration. Heavy metals contamination was not found to be a concern, with only minor levels of mercury being detectable. Two studies reviewed in 2007 found no impurities.[41]
Most folks work a 9 to 5 position but if you’re not in the corporate world yet then odds are you’re a student with classes scattered throughout the day and it takes up the vast portion of your free time. That being said, you’re likely going to have to work out in the morning or the evening in order to fit in your session amidst the hectic commitments in your everyday life. Here are a few things to consider in regards to each time period:
In muscle cells, the creatine transporter is predominantly localized to the sarcolemmal membrane. Western blot analysis of creatine transporter expression revealed the presence of two distinc protein bands, migrating at 55kDa and 70kDa on reducing SDS-PAGE gels.[147][148] The 73kDa band has been reported to be the predominant band in humans, with no differences based on gender.[148] A more recent report demonstrated that the 55kDa creatine transporter variant is glycosylated, forming the 73 kDa protein. Therefore, the 55 and 75kDa protein bands are actually immature and mature/processed forms of the creatine transporter protein, respectively.[149]
Make no mistake: Eating for muscle is just as important as lifting for muscle. The foods you grab in the morning on the way to work, the meals you pack for lunch and mid-afternoon, what you put into your body immediately following your workout, and your final meal of the day impact your results as much as, if not more than, the number of reps you squeeze out at the end of a set. But in reality, it can be tough to stick to a "“clean"” diet when you'’re busy. We know that adding another layer of complexity to life in the form of reading food labels and studying ingredient lists just isn'’t an option for most of us. Not to mention actually preparing all those healthy meals.

Gain mass: One of the most popular reasons for people to take body building supplements is to gain weight and that is why protein powder is much sought after. Protein is the building block of muscles and therefore, bodybuilders use protein powder to help repair muscles, speed recoveries and preserve muscle mass. They usually consume 1 to 2 grams of protein per pound of body weight every day. 


^ Jump up to: a b Sapienza P, Zingales L, Maestripieri D (September 2009). "Gender differences in financial risk aversion and career choices are affected by testosterone". Proceedings of the National Academy of Sciences of the United States of America. 106 (36): 15268–73. Bibcode:2009PNAS..10615268S. doi:10.1073/pnas.0907352106. PMC 2741240. PMID 19706398.

If you'’re looking to add muscle mass to your frame, hitting the weights hard is a given. Quality time in the gym begins a cascade of changes that will stimulate your muscles to grow bigger in response to the challenges you throw their way. It'’s tempting to think that'’s all it takes to add muscle to your body. After all, you can actually feel your biceps growing after an intense set of curls.
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