Testosterone is most commonly associated with sex drive in men. It also affects mental health, bone and muscle mass, fat storage, and red blood cell production. Abnormally low or high levels can affect a man’s mental and physical health. Your doctor can check your testosterone levels with a simple blood test. Testosterone therapy is available to treat men with low levels of testosterone. If you have low T, ask your doctor if this type of therapy might benefit you.

Stand lunge-length in front of a bench making sure your knee does not extend past your toes. Hold a dumbbell in each hand and rest the top of your left foot on the bench behind you. Lower your body until your rear knee nearly touches the floor and your front thigh is parallel to the floor. Then push through the heel of your front foot to return to standing, keeping the back foot on the bench. Repeat for required reps then switch legs.


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 proper warm-up is an important part of an effective strength workout. Start by foam rolling your muscles to wake 'em up. "Foam rolling loosens up tight muscles so that they work the way they're designed to," says Davis. A dynamic warm-up is another important part of your pre-workout routine, it preps your muscles for the work they're about to do and helps increase your range of motion. Increasing your range of motion allows you to go deeper into those squats and fully extend those bicep curls, which means more muscle recruitment and better results. "These two combined reduce your risk of injury and allow you to push harder during your workout," says Davis. Get started with this five-minute warm-up.

No. It’s not easy for everyone to get the recommended amount of protein in their diets through good eating habits alone. Others may not have clinically low testosterone, but still benefit from boosting their levels to improve their muscle building capacity. You can fix these common problems through muscle building supplements. These easy to take pills and powders can also help you boost your performance at the gym which will, in turn, spur your body’s muscle building and recovery response.


Despite a possible decreasing creatine content in the muscles when maintenance is deemed suboptimal, the overall retention of weight and lean mass is merely additive over time. This is thought to be due to increases in skeletal muscle production (increase in body weight) compensating for the progressive declines in water and glycogen content (decreases in body weight).
In addition to the BBB, SLC6A8 is also expressed on neurons and oligodendrocytes,[192] but is relatively absent from astrocytes, including the astrocytic feet[193][194] which line 98% of the BBB.[195] Creatine can still be transported into astrocytes (as well as cerebellar granule cells) via SLC6A8, as incubation with an SLC6A8 inhibitor prevents accumulation in vitro. It seems to be less active in a whole brain model, relative to other brain cells.[196]
GLUTs are vesicle transporters that are the rate-limiting steps for bringing glucose into a cell, and GLUT4 is the most active variant.[327] Agents that reduce blood glucose (insulin or AMPK) are known to act via mobilizing GLUT4, and increased GLUT4 expression and activity is indicative of a greater ability to bring glucose into a cell, while reducing it impairs glucose uptake.[328] Rat studies have confirmed that creatine feeding increases muscular GLUT4 expression associated with increased insulin-stimulated glucose uptake.[329]
Testosterone is necessary for normal sperm development. It activates genes in Sertoli cells, which promote differentiation of spermatogonia. It regulates acute HPA (hypothalamic–pituitary–adrenal axis) response under dominance challenge.[22] Androgen including testosterone enhances muscle growth. Testosterone also regulates the population of thromboxane A2 receptors on megakaryocytes and platelets and hence platelet aggregation in humans.[23][24]
Some of these signs and symptoms can be caused by various underlying factors, including medication side effects, obstructive sleep apnea, thyroid problems, diabetes and depression. It's also possible that these conditions may be the cause of low testosterone levels, and treatment of these problems may cause testosterone levels to rise. A blood test is the only way to diagnose a low testosterone level.
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]
Bench Press. The bench press is about as American as apple pie, fireworks, or bald eagles. If you’re in a gym on a Monday, then you can pretty guarantee at least 85% of the males in the building will be benching. With good reason though, variations such as the flat bench barbell or dumbbell press and the incline bench barbell or dumbbell press are very effective mass builders for the chest, shoulders, and triceps.
As you grow older, an active life is more important than ever. Even as the world tells you it's time to retire, relax, and take it easy, your body is craving for you to keep moving. And though you may be ready to retire from your 9-5, don’t hang up your walking shoes quite yet. The truth is that if you really want to enjoy these golden years and get more quality time from them, your best strategy is to exercise regularly.

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.

I always recommend starting on the low end of the scale. Only increase volume when you absolutely need to. So, if you’re training chest, you could do 6 work sets of dumbbell bench presses to start out, breaking down to two sets per workout for three sessions per week. You can gradually add sets from there, experimenting with different training splits that will allow you to get in more volume without overtraining (we’ll discuss training splits next).
Post workout, it’s important to restore your body’s energy by consuming protein and carbs. When you’re trying to build muscle, this is an especially important step. Protein powder is a great muscle builder for your post-workout routine, as long as you include a carbohydrate as well. You can get this by eating a banana or adding oats or banana to your protein shake. Or simply cook up a batch of healthy oatmeal muffins and include protein powder in your recipe. Then, enjoy your post-workout supplement as a delicious snack!
Sound complicated? Fortunately, there's an easy rule of thumb for increasing your training volume: For each exercise, perform three to six sets of six to 12 reps, resting for 30 to 90 seconds between each set, she says. The weight used should be enough that you can get out your last reps with proper form but wouldn't be able to perform any additional reps.
Holding a kettlebell in your left hand, stand on your right foot and lift your left foot off the ground.. Keeping your weight in your midfoot to heel, inhale as you hinge at your hips and slightly bend your knee to push your butt backward. Keep your shin vertical and hips squared forward. Exhale as you drive through your heel to return to standing. Do 10-12 reps. Switch sides.
Although creatine can be bought commercially as a standalone product it is often found in combination with other nutrients. A prime example is the combination of creatine with carbohydrate or protein and carbohydrate for augmenting creatine muscle retention [5] mediated through an insulin response from the pancreas [69]. Steenge et al [70] found that body creatine retention of 5 g CM was increased by 25% with the addition of 50 g of protein and 47 g of carbohydrate or 96 g carbohydrate when compared to a placebo treatment of 5 g carbohydrate. The addition of 10g of creatine to 75 g of dextrose, 2 g of taurine, vitamins and minerals, induced a change in cellular osmolarity which in addition to the expected increase in body mass, seems to produce an up regulation of large scale gene expression (mRNA content of genes and protein content of kinases involved in osmosensing and signal transduction, cytoskeleton remodelling, protein and glycogen synthesis regulation, satellite cell proliferation and differentiation, DNA replication and repair, RNA transcription control, and cell survival) [25]. Similar findings have also been reported for creatine monohydrate supplementation alone when combined with resistance training [71].
Cornelissen, V. A., Defoor, J. G., Stevens, A., Schepers, D., Hespel, P., Decramer, M., Mortelmans, L., Dobbels, F., Vanhaecke, J., Fagard, R. H., and Vanhees, L. Effect of creatine supplementation as a potential adjuvant therapy to exercise training in cardiac patients: a randomized controlled trial. Clin.Rehabil. 2010;24(11):988-999. View abstract.
Beginners are advised to build up slowly to a weight training program. Untrained individuals may have some muscles that are comparatively stronger than others; nevertheless, an injury can result if (in a particular exercise) the primary muscle is stronger than its stabilizing muscles. Building up slowly allows muscles time to develop appropriate strengths relative to each other. This can also help to minimize delayed onset muscle soreness. A sudden start to an intense program can cause significant muscular soreness. Unexercised muscles contain cross-linkages that are torn during intense exercise. A regimen of flexibility exercises should be implemented before weight training begins, to help avoid soft tissue pain and injuries.
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.
In general, muscle content of creatine tends to be elevated to 15-20% above baseline (more than 20mM increase) in response to oral supplementation. People who get a sufficiently high influx of creatine are known as responders.[150][151][152][153] A phenomena known as “creatine nonresponse” occurs when people have less than a 10mM influx of creatine into muscle after prolonged supplementation.[154] Quasi-responders (10-20mM increase) also exist.[154] Nonresponse is thought to explain instances where people do not benefit from creatine supplementation in trials, since some trials that find no significant effect do find one when only investigating people with high creatine responsiveness.[155] There are clear differences between those who respond and those who do not, in regard to physical performance.[156] People who are creatine responsive tend to be younger, have higher muscle mass and type II muscle fiber content, but this has no correlation with dietary protein intake.[154][157]
Creatine supplementation often causes weight gain that can be mistaken for increase in muscle mass. Increasing intracellular creatine may cause an osmotic influx of water into the cell because creatine is an osmotically active substance [10]. It is possible that the weight gained is water retention and not increased muscle. The retention of water may be connected to reports of muscle cramps, dehydration, and heat intolerance when taking creatine supplements. It would be prudent to encourage proper hydration for creatine users. Further research is needed to investigate these and other possible side effects.

Supplementation of a loading phase of creatine has been noted to augment the increase in RBC levels of superoxide dismutase (SOD) from exercise, when measured immediately after, by 8.1%, but control groups increased to match within an hour.[299] Glutathione (normally decreases with exercise) and catalase (increases) were both unaffected,[299] and elsewhere in vitro red blood cells incubated with 3mM of creatine (within the supplemental range) is able to improve filterability (a measure of cell rheology, or fluid structure of the cell[300]) when RBC creatine was increased by 12.3% to reach 554µM.[301] This was thought to be due to reduced oxidative stress (assessed via MDA) in the red blood cells, which in the presence of 1-5mM creatine was progressively reduced by 20-41%.[301]
2-[carbamimidoyl(methyl)amino]acetic acid, Cr, Creatin, Creatina, Créatine, Créatine Anhydre, Creatine Anhydrous, Creatine Citrate, Créatine Citrate, Creatine Ethyl Ester, Créatine Ethyl Ester, Creatine Ethyl Ester HCl, Créatine Ethyl Ester HCl, Creatine Gluconate, Creatine Hydrochloride, Créatine Kré Alkaline, Creatine Malate, Créatine Malate, Creatine Monohydrate, Créatine Monohydrate, Créatine Monohydratée, Creatine Pyroglutamate, Créatine Pyroglutamate, Creatine Pyruvate, Créatine Pyruvate, Dicreatine Malate, Dicréatine Malate, Di-Creatine Malate, Éthyle Ester de Créatine, Glycine, Kreatin, Kre-Alkalyn Pyruvate, Malate de Tricréatine, N-(aminoiminométhyl)-N-Méthyl, N-(aminoiminomethyl)-N methyl glycine, N-amidinosarcosine, Phosphocreatine, Phosphocréatine, Tricreatine HCA, Tricréatine HCA, Tricreatine Malate, Tricréatine Malate.


Standing with your feet hips distance apart, hold a barbell or free weights at shoulder height (either the barbell resting above your shoulder blades on your back, or free weights resting on top of your shoulder muscles held in front of you). Keeping your spine in a neutral position move into the squat by retracting your hips and pulling them backward. Hinging at your hips, bend your knees until your thighs come almost parallel to the ground (knees should be directly over your feet). Then push back up until your back is straight and repeat 5–10 times depending on the weight you’re using.
However, testosterone is only one of many factors that aid in adequate erections. Research is inconclusive regarding the role of testosterone replacement in the treatment of erectile dysfunction. In a review of studies that looked at the benefit of testosterone in men with erection difficulties, nearly half showed no improvement with testosterone treatment. Many times, other health problems play a role in erectile difficulties. These can include:
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 males, testosterone is synthesized primarily in Leydig cells. The number of Leydig cells in turn is regulated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In addition, the amount of testosterone produced by existing Leydig cells is under the control of LH, which regulates the expression of 17β-hydroxysteroid dehydrogenase.[132]

Competitive and professional bodybuilders, however, can often build up to two to three pounds of muscle per month during dedicated bulking periods. "But they are living and breathing muscle growth. They aren't just in and out of the gym like most people," Simpson says, noting that under extreme conditions, hyperplasia, or the growth in the number of muscle cells in a given muscle tissue, may actually occur, further adding to muscle growth results.
Based on the limited data on performance and safety, some authors have not identified any conclusions and do not recommend its consumption in regards to creatine supplementation in children and adolescents [52,54]. Conversely, according to the view of the ISSN [5], younger athletes should consider a creatine supplement under certain conditions: puberty is past and he/she is involved in serious competitive training; the athlete is eating a well-balanced caloric adequate diet; he/she as well as the parents approve and understand the truth concerning the effects of creatine supplementation; supplement protocols are supervised by qualified professionals; recommended doses must not be exceeded; quality supplements are administered.
The muscle endurance objective is pursued when you want your muscles to be able to perform the same motions over an extended period of time or in other words when you want your muscles to be strong and not become tired rapidly. You'll want to use at least 4 sets from which at least 16 repetitions are performed. The muscle endurance objective is often used for muscles in your lower body, such as those located in your legs or your buttocks.
Some people recommend first “loading” creatine (typically consuming 5 g 4 times a day for 5 to 7 days). This isn’t necessary though, for muscle stores will be saturated regardless after a few weeks. Remember that you can also use creatine as an alternative to things like caffeine to acutely to ward off some of the negative consequences of sleep loss.
Secure a flat resistance band just above your ankles and stand with your feet at about hip width, keeping feet forward. Keeping your weight in your heels, step your right foot laterally, maintaining the tension in the band. Keep the band taut as you step your left foot slightly to the right. Continue stepping sideways to your right for about 5 steps. Then step to your left to return to the starting position. Repeat three times.
How to do it: Balance on your right foot, keeping your midsection tight and shoulders back and down. Bend at the waist with both of your hands out to the sides and extend your left leg back as you fire the left glute. Your shoulder and heel should move together, forming a straight line. Return to starting position and switch legs, performing a set of 10 on each leg.
How to do it: Begin with your head, neck, and shoulders comfortably fixed against a stability or Swiss ball and both feet firmly planted on the ground, knees bent at 90°. (This is also known as table top position.) Either stretch your arms straight up above your chest with your hands clasped to maximize the balance and stability challenge, or down on either side in case you begin to slip or tip over. As with the other bridge motions, simply lower your hips toward the floor then drive them toward the ceiling. Lower and repeat.

Prevents disease and degenerative conditions: Heart disease is the leading cause of death for both men and women; Strength training helps correct issues relating to cholesterol, high blood pressure, obesity, diabetes, and inactivity – all factors for heart disease. Cardiologists are even starting to recommend strength training for people who have suffered a heart attack as little as three weeks after the attack. Who knows, maybe one day your cardiologist will tell you to do some “cardio” and he’ll be referring to strength training!
In regard to liver fat buildup (steatosis), which is normally associated with reduced availability of S-adenosyl methionine[495][496] and a suppression in expression of genes involved in fatty acid oxidation (PPARα and CPT1), creatine supplementation at 1% of the rat diet alongside a diet that induces fatty liver is able to fully prevent (and nonsignificantly reduce relative to the control given standard diets) the aforementioned changes and the state of steatosis, as well as changes in serum biomarkers (glucose and insulin) that accompany steatosis.[125] 
K. Aleisha Fetters, M.S., C.S.C.S., is a Chicago-based personal and online trainer. She has a graduate degree in health and science reporting from the Medill School of Journalism at Northwestern University and regularly contributes to Men's Health, Women's Health, USNews.com, TIME, and SHAPE. When she's not lifting something heavy, she's usually guzzling coffee and writing about the health benefits of doing so.

Creatine is a non-protein amino acid found in abundance in animal foods such as red meat and fish. A pound of either contains roughly 1 to 2 g of creatine. About 95% of bodily creatine is stored in skeletal muscle, roughly two-thirds of which is phosphocreatine and one-third of which is free creatine. Other creatine storage depots include energy-hungry organs such as the brain and testes.

The researchers found that the dose of testosterone required to produce different effects in the body varied widely. The influence of testosterone and estradiol also differed. As the testosterone gel dose was reduced, the scientists showed, reductions in lean mass, muscle size, and leg-press strength resulted from decreases in testosterone itself. In contrast, increases in body fat were due to the related declines in estradiol. Both testosterone and estradiol levels were associated with libido and erectile function.
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.
I’m 6 foot and 154 pounds and I’m thinking of using this diet to bulk up before I do a cut to shed body fat for a more lean look. How good would this diet be to maintain body fat while building muscle and how much muscle could you expect to put on. Thanks. I do not want to gain that much body fat while bulking and if possible I would just like to maintain my current body fat while bulking.
In males, testosterone is synthesized primarily in Leydig cells. The number of Leydig cells in turn is regulated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In addition, the amount of testosterone produced by existing Leydig cells is under the control of LH, which regulates the expression of 17β-hydroxysteroid dehydrogenase.[132]

Hartman, J. W., Tang, J. E., Wilkinson, S. B., Tarnopolsky, M. A., Lawrence, R. L., Fullerton, A. V., & Phillips, S. M. (2007). Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters. The American Journal of Clinical Nutrition, 86(2), 373-381.
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]
What happened was that, statistically speaking (less than 5% chance what was observed was due to chance means ‘significant’ for this study) there was no significant difference between pre- and post- workout, meaning that both were equally effective. This protocol did note that both groups found benefits with creatine supplementation, but they both found the same amount of benefit.
The right amount of workout: It is highly possible that the protein powder you are taking doesn’t work on your body. Supplements should only be taken if you have a rigorous workout schedule or else, it will turn out to be of no value. Most people just purchase a box of supplements without really doing the math, which is very important. Unless you find out the dosage that suits you, the amount of time you should dedicate for the workout and so on, you must not expect daydream the results. 
Another double-blind study supplemented with 18.75 g/day of creatine monohydrate for 5 days prior to high-intensity intermittent work to exhaustion, and then 2.25 g/day during testing. The workouts consisted of cycling to exhaustion using several protocols: (a) nonstop, (b) 60 seconds work/120 seconds rest, (c) 20 seconds work/40 seconds rest, and (d) 10 seconds work/20 seconds rest. Creatine supplementation significantly increased the total work time for all four protocols [13].
Remember, this is for the extreme skinny guy...But I want you to start hitting a buffet once a week. Try and position this eating frenzy after a hard workout so that the majority of calories get shuttled into the muscles which will really help you pack on those pounds and gain weight in the right places. Don't go too overboard, but this will train your body to 'accept' more food and it will increase your appetite in the days to come. Take advantage of this strategy.
These effects were noted before in a preliminary study of depressed adolescents (with no placebo group) showing a 55% reduction in depressive symptoms at 4g daily when brain phosphocreatine levels increased.[231] Other prelimnary human studies suggest creatine might lessen unipolar depression[256] and one study on Post-Traumatic Stress Disorder (PTSD) noted improved mood as assessed by the Hamilton Depression Rating Scale.[232]
Overtraining occurs when a bodybuilder has trained to the point where his workload exceeds his recovery capacity. There are many reasons why overtraining occurs, including lack of adequate nutrition, lack of recovery time between workouts, insufficient sleep, and training at a high intensity for too long (a lack of splitting apart workouts). Training at a high intensity too frequently also stimulates the central nervous system (CNS) and can result in a hyperadrenergic state that interferes with sleep patterns.[51] To avoid overtraining, intense frequent training must be met with at least an equal amount of purposeful recovery. Timely provision of carbohydrates, proteins, and various micronutrients such as vitamins, minerals, phytochemicals, even nutritional supplements are acutely critical. A mental disorder informally called “bigorexia” (by analogy with anorexia) may be held accountable of some people overtraining. Sufferers feel as if they are never big enough or muscular enough, which forces them to overtrain in order to try and reach their goal physique.[52]
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.
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.
There are many camps within the weight training fitness community. We have bodybuilders, Crossfit athletes, powerlifters, Olympic lifters, and strongman athletes just to name the most popular ones off the top of my head. One thing they all have in common is that they all use resistance to achieve a particular goal. They all also “share” particular exercises. Most resistance-training athletes do barbell squats, overhead presses and deadlifts. I can write pages of differences between each of the disciplines I listed above and I can also write quite a bit about their similarities but one form of resistance training is MORE different than the others. Bodybuilding is the only sport that judges the appearance of the athlete rather than their performance. This may be why bodybuilders tend to get poked at the most.

In other primates, gluteus maximus consists of ischiofemoralis, a small muscle that corresponds to the human gluteus maximus and originates from the ilium and the sacroiliac ligament, and gluteus maximus proprius, a large muscle that extends from the ischial tuberosity to a relatively more distant insertion on the femur. In adapting to bipedal gait, reorganization of the attachment of the muscle as well as the moment arm was required.[4]


From a standing position, balance yourself on your left leg. With your right leg straight and slightly off the floor, perform small circles (from the hip) in front, to the side, and then behind you. Aim for 3-5 circles both clockwise and counterclockwise at each angle. Your supporting leg glutes will be firing to stabilize your pelvis so be sure to stand tall and strong – no swaying.
An obvious use case is injury rehabilitation. Creatine has sometimes (not always) been shown to improve responses to rehabilitation protocols. Related to this, a very rigorous review of all studies that explored effects of creatine in treating skeletal muscle disorders unambiguously showed that creatine improves muscle strength and quality of life in muscular dystrophy patients.

Like other steroid hormones, testosterone is derived from cholesterol (see figure).[128] The first step in the biosynthesis involves the oxidative cleavage of the side-chain of cholesterol by cholesterol side-chain cleavage enzyme (P450scc, CYP11A1), a mitochondrial cytochrome P450 oxidase with the loss of six carbon atoms to give pregnenolone. In the next step, two additional carbon atoms are removed by the CYP17A1 (17α-hydroxylase/17,20-lyase) enzyme in the endoplasmic reticulum to yield a variety of C19 steroids.[129] In addition, the 3β-hydroxyl group is oxidized by 3β-hydroxysteroid dehydrogenase to produce androstenedione. In the final and rate limiting step, the C17 keto group androstenedione is reduced by 17β-hydroxysteroid dehydrogenase to yield testosterone.
While the number of reps you do per set is important, of equal importance is the total number of reps you do per muscle group. The National Strength and Conditioning Association has determined that, to maximize growth, you need approximately 20–70 total reps per muscle group. Depending on which end of a rep range you’re working, this can be done in one session or over a few days (a training week, for instance), but that’s the spread you need to cover to see gains.
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