Weight Training Effects on Libido & Erections

I’ve seen some bodybuilders complain in forums, that ever since they started weight training they have lower libido or even erectile dysfunction (ED) problems. Like many other bodybuilders, I always thought weight training promoted healthy testosterone levels, so it wouldn’t have this effect. It wasn’t until I started studying the hormonal reactions from weight training recently, that I realized it certainly could have an effect.

Within about an hour of starting a weight training workout, there will be a spike in cortisol. There will also be a spike in testosterone and other hormones. A few hours later though, testosterone will drop quickly below normal pre-training levels. They won't return to pre-training levels for a day or 2. Testosterone plays a crucial role in men, for libido and erections. I believe during the time it is well below normal, is when problems libido or ED problems could occur.

Excessive weight training (overtraining) would just make the problem even worse. Bodybuilders sometimes find that they're sex drive goes up when they take a couple weeks off. This is because taking a break off does restore your hormone levels, if you have been overtraining or gone months without any breaks from lifting. After reading this you may, think that bodybuilding does more harm than good for healthy hormonal levels. In the long run however, bodybuilding will help maintain (or slightly increase) your resting testosterone levels, provided you aren't overtraining. It is just during the period of immediate recovery for about 24 to 36 hours, that your testosterone levels drop temporarily. Common diet and supplement practices of bodybuilders, such as high calorie diet and plenty of healthy fats and getting plenty of sleep has been shown to increase natural testosterone production.

Does Weight Training Increase Risk of Hernia?

Hernias are very common in men. While bodybuilders are told how to lift with proper form and breathing, sometimes that is lost when we lift too heavy a weight to show off in the gym.

Hernia studies:

A recent study published in Surgery Volume 141, Issue 2, February 2007, Pages 262-266 was done between 2002 and 2004 on over 1200 people. They were divided into a control or case group on whether they had inguinal hernia. Inguinal hernia is a hernia located in the abdomen, the most common surgical performed hernia. Each person was asked to fill out a standard questionnaire. The results of the study showed that chronic obstructive airway disease was a risk factor for direct hernia(one type of inguinal hernia). Family history was a independent predictor for inguinal hernia. Total activity index and family history of hernia, were significantly related to both direct and indirect hernias( two types of inguinal hernias). Family history was the most important cause, not activity index, of inguinal hernia. Those with a positive family history, were 8 more times likely to have one. Total activity index could include a lot of things in a lifestyle, besides weight training. I'm sure most of the people in the study were not weight training.

This study and many others, point to genetics as the most overwhelming risk factor for hernias. Many males will eventually develop the hernia anyways, given enough time. However, I would not brush off the risk with weight training completely. If weight training is not performed correctly you can increase your risk of Hernia. A study published in (European Journal of Epidemiology Volume 8, Number 2 / March, 1992 pg. 277-282) and many other studies, have shown that strenuous exertion jobs or lifestyles increase risk. I believe this increased risk is mainly due to improper form. When your lifting boxes or furniture for a living, your going to wind up having to contort your body in unusual ways to lift it. This will cause a strain on your abdomen and cause a hernia. Lifting barbells and dumbells in contrast, is very easy to pick up and do with proper form. It is important you breath in on the negative portion of the rep and out on the positive. You should lift with your target muscles and not use bad form or cheat to lift a heavy weight. Leave your ego at the door, as cheating to lift a weight will cause strain on your abdomen, which could cause a hernia. When doing squats and deadlifts, also make sure you lift the weight with your legs and not with your abdomen.

What Causes Overtraining?

Bodybuilders always tell newbies to watch how many workout sets they do, to avoid overtraining. The word gets thrown around so much, without anyone describing the cause of overtraining. Many bodybuilders don’t even believe in overtraining. Some bodybuilders have claimed that there is no way to overtrain, just that some people are undereating. I believe this is because most bodybuilders don’t have a true concept of what causes overtraining.

Does overtraining even exist?

Yes. Bodybuilders claiming that overtraining only exists because they aren’t eating enough, is foolish and goes against the laws of basic science. The body works on the law of diminishing returns. In other words, in the beginning eating more might help the body recover better, but it's going to hit a point where increasing calories isn't going to stop overtraining. Think of it as putting safety features on your car. There is only so much you can do to making a car safer, before a really big wreck will still wind up killing you!

How one enters the overtraining state:

Our body at all times, is either in an anabolic(muscle building), catabolic(muscle wasting), or equilibrium state(protein synthesis and breakdown equal). Overtraining is a catabolic state, where you have done too much for your body and it's hormones.

In order to recover completely from a weight training session, the following must happen:

- your muscles must heal from the previous workout
- your CNS (nervous system) must heal
- your cortisol levels must lower to pre-training levels
- testosterone must increase back to normal pre-training levels
- your muscle glycogen must be restored

After a weight training session, it puts stress on all the above factors. If you keep compounding the problem by continuing work out, then things will get worse and you are in an overtraining state.

Does overtraining involve muscle parts or the whole body?

Some people think of overtraining as a specific muscle. Overtraining is much more than just a specific part of the body. Overtraining involves the whole body because testosterone, cortisol, and other hormones are involved. When testosterone levels are low and/or cortisol high, you will be breaking down muscle more than you are building it up. Cortisol is probably the main cause hormonally for entering the overtraining state.

During hormonal levels like this, you would be better off taking a rest than doing a weight training session. Each time you weight train cortisol levels increase and testosterone levels drop. So the last thing you want to do, is weight train again when your hormones are in a catabolic state. Because of this persistent and overwhelming state, overtraining is considered a syndrome.

How does one get out of overtraining state?

Rest. Cortisol blockers might help a little to speed up recovery from this state, but you still will have to wait for your entire body to recover, not just cortisol. Weight training or even daily stress(which causes high long term cortisol levels), will keep you in an overtraining state indefinitely.

Signs of overtraining:

Insomnia, tiredness in the day, aching muscles and joints, high resting pulse, strength loss on lifts, are the most obvious immediate signs you are overtraining. Long term you will notice fat gain and muscle loss.

Squats / Deadlifts and Release of Testosterone and Growth Hormone

In bodybuilding forums, you’ll constantly see bodybuilders tell each other to work on their legs, mainly with squats and deadlift excercises. Most beginner bodybuilders hate working legs and look for an excuse to not work them. They are told it helps release testosterone, growth hormone, and will increase overall body muscle mass. Is there studies that support all these claims?

Testosterone and GH levels after squats & deadlifts:

Resistance training in general, increases testosterone and growth hormone, during and immediately after post excercise. It has been shown in many studies, including a published study Int J Sports Med. 1991 Apr;12(2):228-35 done on both men and women during resistance excercise. Squats and deadlifts increase GH and Testosterone, more than other compound excercises during excercise.

There is however, no significant studies that show that resistance excercise, directly leads to higher hormone levels long term. In fact, for a day or 2 post-excercise, many studies show LH and testosterone decline, while cortisol increases. In other words, building yourself up to a 200 lb ripped bodybuilder doesn't directly increase your testosterone levels, from when you were smaller. But you might though have higher testosterone levels, due to better eating, supplementation, and working out, as a result of the bodybuilding lifestyle. The increased cortisol levels and lower testosterone, is also why overtraining is such an easy state to enter. We have to allow our body to recuperate itself, before doing more weight lifting.

Long term effects from squatting and deadlifting:

The benefit for doing leg excercises, appears from research not to be from increasing long term natural levels of testosterone and GH. I believe however the large burst of testosterone and other hormones during leg excercises, are the major reasons why squats and deadlifts are very important for overall muscle building. It's the same reason why a bench press is more effective mass builder than a chest flye workout. Why? because the compound bench press is going to release more testosterone and GH in a workout than a chest flye.

The large burst of anabolic hormones resulting from squats and deadlifts, allows most of your muscles to benefit from this release simultaneously. Squats and deadlifts work many muscles simultaneously in the body and will allow most of your body to get some stimulation from the release of the hormones during the workout. The testosterone and GH released, is very crucial for being a catalyst for your muscle growth. It won't be released as much in the smaller compound excercises, such as bench press. Therefore doing smaller compound excercises, would not be able to makeup for the benefit of having leg workouts in your routine.

Most experienced bodybuilders know all too well, how important leg excercises are for overall mass. You've probably seen the guys walking in the gym who look like lightbulbs (big upper body, but chicken legs). That has made many bodybuilders question the idea that leg excercises always equals bigger upper body. One must keep in mind we don't know if they are using steroids, which would make it a little easier to gain upper body mass without leg excercises. On the flipside, it would also be harder post cycle for a steroid user just to keep his gains. These people probably also have excellent upper body genetics and years of training experience. If they worked harder on leg excercises, they would be even bigger.

Effect of Ejaculation (Sex) on Bodybuilding Gains

The question on whether ejaculation (or sex) before workouts will effect their strength or muscle gains, is a common question for many bodybuilders. Athletes have also have been debating this question for years. Some believe that ejaculation before an athletic event will help their performance, while others believe it should be done after or even abstained completely. In this article I will discuss the hormonal effects of ejaculation on the body and when (or if) it should be avoided

Effects on testosterone during sexual arousal and ejaculation:

Testosterone level have been found in research to rise in humans after sexual stimuli (such as sexually explicit pictures). One study like this was published in New Scientist 22 Aug 98 11, done by Ludwig Boltzmann Institute for Urban Ethology in Vienna. 10 men and 10 women viewed a 15 minute pornographic film. Men's testosterone levels increased 100 percent afterwards, while women's was 80 percent.

Another study published by Psychoneuroendocrinology. 1993;18(3):205-18 used sexually arousing films on 9 males. LH levels (stimulates testosterone production) and testosterone levels increased within 10 minutes of sexually arousal. Other studies have also shown, other types of stimuli may also increase testosterone levels and agression, such as holding a gun.

Studies dealing with testosterone levels and it's effects during sexual acts and ejaculation, seem to be mostly done on animals.  One study done on rats by the Instituto de Neuroetologia, Universidad Veracruzana, Xalapa, Ver., Mexico showed that after 2 ejaculations there was a steep rise in serum testosterone and remained higher even after 4 ejaculations in a row. Another study was done on stallions and mating by the Dipartimento di Scienze Cliniche Veterinarie, Sez. Clinica Ostetrica e Ginecologica Veterinaria. They found that testosterone levels rised 10 minutes after mating and then again 30 minutes into it. Cortisol levels also increased during the mating.

A study by Department of Pharmacobiology, Centro de Investigación y Estudios Avanzados was done on rats to measure sexual satiety and androgen receptors. The rats were measured after a sexual encounter. They measured the testosterone levels afterwards and found no change. They also measured a drop in angrodren receptor density, in the MPOA-medial part of the brain. This receptor density returned 72 hours later. It appears from this study, the lack of sexual desire post ejaculation, may have been from changes in the brain, not from changes in testosterone.

A study by the Department of Reproductive Biology, Universidad Autonoma Metropolitana-Iztapalapa found that testosterone levels stayed the same or rised, after various types of sexual encounters in male rats. The more experienced rats had a large increase in testosterone post-ejaculation, which remained even 24 hours afterwards. The sexually inexperienced rats however, had little change in testosterone post sexual encounter. This study suggests that sexual experience and execution, may play a role in the rise of testosterone.

Long term testosterone levels from abstaining ejaculation:

The only study I could find measuring testosterone levels of men who didn't ejaculation for extended periods of time, was research done by chinese researchers, J Zhejiang Univ Sci. 2003 Mar-Apr;4(2):236-40. The study was done on 28 men who were told to not ejaculate for entire week. It was found that for first 6 days testosterone levels did not change. However, on the 7th day of abstaining, testosterone levels jumped up by nearly 50%. It then declined quickly after that day, therefore abstaining from ejaculation had no long term rising effect.


What do these studies on animals and humans tell us about the relationship between testosterone and sexual activity? Many people have always assumed that after sexual activity, males experience a drop in testosterone levels. There is no research we could find that points to a significant drop in testosterone post-ejaculation. In fact research tells us that the opposite seems to be true. Men will have significant jumps in testosterone levels from sexually arousing stimuli(and certain other types of stimuli). The research also suggests that sexual encounters and ejaculation, will not effect and may increase, testosterone blood levels.

Viewing sexually arousing material, without ejaculating, before working out should be beneficial for improving workouts.  Ejaculating before working out, would probably not be ideal, since ejaculation also releases endorphins(pain killing) natural hormones in the body. This would in turn effect your strength and energy before your workout.

The chinese study also suggests that abstaining from ejaculation will not increase your Testosterone levels long term and hence, not improve your bodybuilding gains.  Recent studies are also showing a significant drop in prostate cancer risk, for men who more frequently ejaculate. According to current research, ejaculation (or sex) is not going to lower your testosterone levels, in either the short term or long term.

Negative (eccentric) reps compared to positive(concentric)

The positive (concentric) and negative(eccentric) portions of a rep, appear to have different effects on muscle growth. Understanding why one does it better than the other, could help us gear our workout routine for optimal muscle growth.

Studies on eccentric and cocentric rep training:

University of Alabama at Birmingham did a study on 10 male and female subjects, who did 8 heavy sets of squats per workout. One workout they did concentric, the other eccentric only contractions. They measured the amounts of IGF-1, IGFBP-4, and Androgen receptors in the muscle. The negative rep stimulated IGF-1 and lowered levels of IGFBP-4(which binds to IGF-1 to make it inactive) better than the concentric. The positive rep increased androgen receptor density (making it more responsive to testosterone) than the negative. From this study, we can see that eccentric reps induce growth more by IGF-1 and the positive mainly from testosterone.

Another study was done at UC Irvine by Ken Baldwin and other scientists, to find the chemical reactions behind eccentric contractions. They also found that they had a significant increase in IGF-1 over positive reps, but also in increasing MGF(mechano growth factor) and the lowering of Myostatin(an important chemical that regulates muscle growth).

Other effects of negative reps:

Besides the differences in hormonal and chemical actions, there is other reasons why eccentric portions of the rep
might be more effective than concentric. Eccentric contractions probably cause more muscle growth, due to the fact they cause more microtrauma on the muscle fibers. The positive portion of the rep causes very little muscle tearing damage compared to the negative portion.

Other possible benefits of negative parts of the rep, may be in the ability to stimulate hyperplasia muscle growth and muscle fascia stretching

Should we do eccentric only training then?:

One might conclude that it is best to do eccentric only training since it is more effective. However, eccentric only training is taxing on the system due to the increased muscle damage it causes.   It  would quickly lead to overtraining, without a subsequent drop in set volume. Doing half negative rep workouts, are also inconvenient and most bodybuilders prefer to be able to use the entire rep range. One alternative would be to modify your regular training routine instead, by lowering the volume slightly and emphasizing the negative portion of the reps more.   Negative emphasize training cannot be used indefinitely because your body will adapt (plateau) to it after a period of time, like with all training techniques.

Muscle Fascia Stretching

You may have heard of the idea of muscle fascia stretching to help increase muscle growth. What is the muscle fascia and is there any scientific evidence these help support muscle growth?

What is the muscle fascia?

Muscle fascia is a very tough material that surrounds individual muscles and muscle groups. It hugs the muscles very tightly.

Research on muscle fascia helping muscle growth:

I could not find any studies, where it directly supported that muscle fascia stretching increases muscle growth. Right now it is mostly based on indirect scientific studies, anatomy, and ancedotal evidence. The theory seems to have got started because people who used to have muscle (or were even fat), had a easier time putting back on muscle, called "muscle memory".

Other supporting evidence, is that bodybuilders who spot inject site enhancement oil. This is where they inject a oil into a muscle in order to bring up a lagging muscle. The most notorious user of this was Greg Valentino, who went overboard and has made his body look ridiculous. Many people assume that the oil is causing temporary muscle gain, but in fact based on user experience it appears to cause actual long term muscle gain as the result of stretching the muscle fascia. Many pro-bodybuilders, such as Olympia winners Jay Cutler and Arnold Schwarzennegar, do forms of weighted fascia stretching as part of their workouts.

It is reasonable to assume from all this, that muscle fascia should help make muscle gains easier. If you are looking for scientific research, surprisingly there is another reason why muscle fascia may help muscle growth. You can read more about it in a previous article I wrote:Does hyperplasia cause growth in human skeletal muscle?

With the evidence on hyperplasia and muscle fascia, I have no doubt that muscle fascia stretching will help boost your muscle growth. I recently started incorporating it into my workouts.

How to stretch the muscle fascia tissue:

Muscle fascia stretching should be done after a good muscle pump from your workout. All fascia stretching is done at the bottom of the negative rep for a good long stretch of 30 seconds to one minute. For example if your doing chest, after your chest workout sets, hold a good long weighted fascia stretch with a chest flye at the bottom. Make sure you don't lower the weight to the point of pain. You should feel a stretch and it should be tough to hold, but it should not be excessive as it will cause injury.

Muscle fascia stretching automatically grow muscle?

No. You will still need to train hard and increase calories and protein. The muscle fascia tissue is stretched which allows the opportunityof muscle growth to happen. If you don't stimulate it by bulking and weight training, you won't notice any gains.

Does hyperplasia cause growth in human skeletal muscles?

The possible role of hyperplasia in muscle growth, is a big debate in excercise science and among bodybuilders. Most bodybuilders accept that it doesn't happen in human skeletal muscle. But are they too easy to dismiss overwhelming evidence?

Two types of muscle growth?

The traditional common belief in muscle growth is in hypertrophy. This theory says that each individual muscle fiber gets thicker due to increased protein retention(due to increased protein synthesis). The increase of size of many individual fibers, in turn makes the entire muscle bigger in diameter.

The opposite theory is hyperplasia. Hyperplasia theory says muscle fibers stay the same, but the muscle cells divide creating more fibers. More fibers at the same size increases the diameter of the muscle overall.

The argument:

No one is arguing that hyperplasia doesn't happen in smooth muscles like the intestines of humans. We have done studies on other animals and know it for certain happens in other animal's skeletal issues. The controversy for experts, comes down to whether the muscle hypertrophy exists in skeletal muscles of humans. The common belief has been that we are born with a certain specific amount of muscle fibers. They believe that muscle hyperplasia is only possible in very abnormal circumstances, such as muscular dystrophy or pregnant women's abdomen.

Studies supporting hyperplasia in animal skeletal muscles:

Dr. Gonyea put weights on cats to test for hyperplasia. His results showed a 20% increase in number of muscle fibers. The results were controversial because scientist said it couldn't apply to humans or because of the method he used to determine new muscle fibers. There have been other studies done on birds and rats that also support hyperplasia for them also.

Studies supporting hyperplasia theory for humans:

Muscle fibers contain tens of thousands of fibers. The problem with doing hyperplasia studies is it involves counting the fibers. Not to mention some of the studies that they do on animals, won't be considered as ethical or possible with humans. It would require the removal of muscle cells causing the tissue is partially destroyed. Luckily, you can still draw conclusions of hyperplasia by using proportions.

Scientists by the name Tesch and Larsson, in 1982 did a fine needle biopsy comparison of 3 groups of athletes: competitive bodybuilders, powerlifters, untrained individuals. Interesting enough the muscle fibers were found smaller in the competitive bodybuilders than in powerlifters and the same size as the untrained. The study was confirmed again when redone in 1986. If hyperplasia is not possible, then how can large bodybuilders have the same muscle fiber diameter as untrained individuals?

Another interesting study done by the American College of Sports Medicine's Medicine and Science in Sport and Exercise found it in powerlifters who use steroids.

Studies supporting muscle hypertrophy theory:

To make matters confusing, there have been multiple studies that show evidence for muscle hypertrophy instead of hyperplasia theory. Using similiar methods of measuring proportions as the previous studies, they found that muscle size increased without a change in muscle fiber number.


Why do the studies give such conflicting results? I personally am of the belief that both hyperplasia and hypertrophy happen. Hyperplasia probably happens only as a result of certain types of training or possibly only from steroid use. That is the only logical explanation I could see from why some studies give different results, yet are scientifically sound. If hyperplasia is possible in other animals and there is supporting research in humans, there is no reason not to strongly believe it happens in humans.

Training to stimulate hyperplasia:

If hyperplasia is possible, which seems highly likely, the next question is, how can we stimulate it? One study by the Journal of Applied Physiology in October 1996 Mechanical overload and skeletal muscle fiber hyperplasia: a meta-analysis seems to help possibly answer that question. They had mechanical overload into 3 groups on several animal species: stretch, excercise, and compensatory. The stretch group had by far the most hyperplasia and the excercise group had the second most.

This research and other studies suggest that emphasis should be put on the negative portion of the rep, especially at the bottom. Slow deliberate negatives on each rep could help stimulate hyperplasia. A much better way to induce hyperplasia however, would be to get a good stretch at the end of a negative rep and hold it. For example, after a few sets of chest excercises, position a weight at the bottom of a chest flye negative portion of rep. Hold the weight at the bottom for a good stretch of about 30 seconds to one minute.

After you are done with back excercises you can get a good long weighted stretch of the lats at the bottom of a negative rep for the bent over row or pullup. Make sure when you do these stretches that you don't overdo it and that you have a nice pump from previous sets. For shrugs you will have to hold the barbell weight behind your back and get a good stretch.

Arnold Schwarzennegar was known for holding the weight and getting a good squeeze when doing chest flyes after a good chest workout. He also was known for having one of the best chests ever. As you seen from this article, it probably was more than coincidental.

There is yet another reason why a good deep static stretch could be stimulating to muscle growth, besides stimulating hyperplasia. The answer is due to the fact it will also stretch muscle fascia. I wrote a article on the issue here: Muscle fascia stretching

Muscle Size Proportional to Strength?

The ultimate goal of male bodybuilders is to increase muscle size as much as possible. We all have heard theories from bodybuilders about what causes strength and how it relates to muscle size. Is strength gains necessary to gain muscle or is muscle gains needed to gain strength? or perhaps science suggests there is no connection between muscle size and strength? Read on to find out the answer.

Studies have shown that muscle tissue has similiar "strength" in all people of equivalent sizes. They measure muscle size by cross sectional diameter and then testing the power output of a muscle fiber. If this is the case, then why do some people of similiar muscle size seem to be vary widely in strength during training?

Strength during actual weight lifting, is a result of a variety of factors. When you are an experienced powerlifter/bodybuilder, your weight training experience has adapted you to have a stronger neural connection. This allows you to be stronger than lesser experienced individuals. The type of training you do also can effect how strong these neural connections get. For example, people who do lower reps and heavier weight, can get stronger than those who do higher reps and lighter weight.

Some people are also naturally stronger per unit of muscle, due to anatomical differences. There have been studies showing muscle attachments can determine your natural strength. In other words, some people naturally start at a higher strength level before even lifting their first weight.

You may have heard it said here and elsewhere, that increasing strength ultimately leads to muscle gain. We know this to be false from experience, as we all know those skinny hardgainers who get much stronger, but never seem to gain a pound of muscle. Olympic gymnast often get much stronger without gaining substantial amount of mass. The increase in strength without muscle mass, is due to lack of calories in the hardgainers and very low reps and high weight in the olympic gymnast.

There is a limit how much strength you can ultimately gain without size. This is why you won't see small guys in any powerlifting competitions. One thing that will always be true, is if you gain muscle, strength will ALWAYS follow. If each muscle fiber has the same amount of strength, then the more you gain you should have a proportional increase in strength. If you aren't getting stronger, then you aren't gaining significant muscle. Sometimes strength can plateau because of lack of sleep or a hectic schedule, but in the long run you should get stronger if you gain muscle. Therefore, strength gains is probably the best indicator of actual muscle gains when trying a supplement or steroid, to see how well it works.


It can be kind of confusing to keep track of everything, so let's summarize it. Each pound of muscle inherently has roughly the amount of strength regardless of bodytype, training, or sex. Your strength during training, is the result of muscle size and anatomical differences and training experience. Muscle gains always lead to strength gains, but strength gains do not always produce muscle gains.

How does weight training cause muscle growth?

One of the most core questions for every bodybuilder, is what are the mechanisms that cause muscle growth? Perhaps if we knew exactly the mechanisms, we could gear a diet and training routine around it. Let's discuss some of the major theories out there and the merit of them.

Muscle Damage Theory:

This theory will make a lot of sense to the novice bodybuilder, who is so sore they can barely walk after their first squat workout. Originally people thought lactic acid was the cause of muscle soreness and damage. It wasn't until they actually took a electron microscopic biopsy of the muscle tissue, that they could see what really happened.

They discovered that a small portion of the fibers had a disorderly pattern. They coined the term to describe this "micro tears". Upon further research they found that eccentric(the negative portion of a rep), did better than the positive in inducing this micro tear. The negative portion is therefore probably more important for muscle growth.

Muscle growth and hormone involvement:

We have been just focusing at the muscle aspect, but the whole body is involved in muscle growth and recovery through the
release of hormones. Muscle damage theory doesn't really answer a lot of questions. That is where another theory comes into play called, substrate accumulation theory. The theory basically believes, that muscle growth is a result of the release of the cascade of anabolic hormones post-workout.

We know the body releases and regulates levels of growth hormone, IGF-1, cortisol, adrenaline, testosterone, during and for many hours post-workout. The most important hormone involved during the muscle building process seems to be testosterone. Testosterone levels will dip low and not reach their peak again until somewhere around 48 hours after weight training.

The longest time protein synthesis lasts post workout for a muscle, is about 48 hours, but often lasts far less than that. Excessive cortisol levels, that start to increase post-workout, must go to a low level quickly again or else overtraining happens.

Which muscle growth theory is correct?

Both theories have flaws when looked at them independantly. For example, if you believed in substrate accumulation theory exclusively, then you would believe that taking a bunch of steroids without weight training could cause muscle growth.   You need muscles to be stimulated plus the hormonal response.  Both theories however, work well together. When they are put together, it seems to be the most plausible explanation.

Muscle Hyperplasia theory:

Unfortunately, it doesn't stop with those two theories. Another major theory is based on hyperplasia, which is a very controversial. Due to the complexity of this theory I wrote my own exclusive article on it: Does Hyperplasia Cause Growth in Human Skeletal Muscles?. It provides some interesting insight, including how to possibly stimulate hyperplasia, that you won't find anywhere else.

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