Thread: Testosterone, IGF-1, and Training.

A Study:

Title: Mechanical load increases muscle IGF-I and androgen receptor mRNA concentrations in humans.

Researchers: Bamman MM, Shipp JR, Jiang J, Gower BA, Hunter GR, Goodman A, McLafferty CL Jr, Urban RJ.

Institution: Department of Surgery, University of Texas Medical Branch, and 2 Metabolism Unit, Shriners Hospitals for Children, Galveston, Texas 77550 Source: American Journal of Physiology Endocrinology & Metabolism. 2001 Mar;280(3):E383-90.

Summary: These investigators looked at the effects of concentric (CON) reps vs. eccentric (ECC) reps on muscle insulin-like growth factor-1 (IGF-I) mRNA concentration. They hypothesized a greater IGF-I response after ECC compared with CON.

Methods: Ten healthy subjects (Average age 24.4 yrs) completed eight sets of eight CON or ECC squats separated by 6-10 days. IGF-I, IGF binding protein-4 (IGFBP-4), and androgen receptor (AR) mRNA concentrations were determined in vastus lateralis from muscle biopsy before and 48 h after ECC and CON. Serum total testosterone (TT) and IGF-I were measured serially across 48 h, and serum creatine kinase activity (CK), isometric maximum voluntary contraction (MVC), and soreness were determined at 48 h.

Results: IGF-I mRNA concentration increased 62% and IGFBP-4 mRNA concentration decreased 57% after ECC. The direction of these changes after CON were similar but not statistically significant. AR mRNA concentration increased after ECC (63%) and CON (102%). Serum levels of total testosterone and IGF-I showed little change. MVC fell 10% and CK rose 183% after ECC squats. Perceived soreness was higher after ECC compared with CON.

Conclusion: Results indicate that a single bout of mechanical loading in humans alters activity of the muscle IGF-I system, and the enhanced response to ECC suggests that IGF-I may somehow modulate tissue regeneration after mechanical damage.

Discussion: Nothing in this study should really surprise us. But it does shed light on how lifting weights selectively regulates anabolic activity to specific tissues of the body. Training increased both androgen receptors as well as muscle specific IGF-1.

Training causes an increase in androgen receptors (testosterone receptors) on muscle cells, which increases the sensitivity of your muscle to your natural testosterone levels. This effect of training on androgen receptors is specific to muscle tissue. In other words, you are not going to see an increase in the effects of testosterone in other tissues such as your hair or your skin. So unlike using steroids, training only increases the effects of testosterone in muscle tissue.

IGF-1 is another critical player in muscle growth. Muscle growth from weight training is the result of IGF-1 being produced by the muscle cells themselves, not the liver. In fact, IGF-1 from the liver is genetically different from IGF-1 produced in your muscles. This is the reason why using IGF-1 systemically (from the blood stream) has been a hit and miss proposition.

IGF-1 formation in muscle tissue is absolutely critical if significant muscle hypertrophy is to occur. IGF-1 produced inside muscle cells that have been damaged by heavy training, oozes out of the cell and activates satellite cells. These satellite cells then donate nuclei to the damaged muscle cell, thereby allowing it to grow larger than before. There is a limit to the size of a muscle cell, and it depends largely on the number of nuclei it has. If you prevent a muscle cell from getting more nuclei from satellite cells, it simply will not grow, no matter how heavy things get. (1,2,3) The reduction in IGF binding protein-4 (IGFBP-4) leads to increased IGF-1 activity.(4) [Note: IGFBP-"3" also binds IGF-1 but in a good way. IGFBP-3 is the main carrier of IGF-1 and prolongs the half-life of IGF-1]

I would like to voice my strongly held opinion that the ever so slight changes in systemic hormone levels as a result of exercise are not responsible for the muscle growth observed with resistance exercise. Instead, as this study illustrates, it is the changes that occur within the muscle cells themselves that account for any hormonal contributions to hypertrophy. Both an increase the muscle's sensitivity to existing androgen levels, increases in intracellular IGF-1 levels, with concomitant decreases in inhibitory IGF binding proteins are the primary "hormonal" mechanisms for muscle growth as a result of training (excluding the use of exogenous hormones).

1. Rosenblatt JD, Parry DJ., Gamma irradiation prevents compensatory hypertrophy of overloaded extensor digitorum longus muscle. J. Appl. Physiol. 73:2538-2543, 1992

2. Rosenblatt JD, Yong D, Parry DJ., Satellite cell activity is required for hypertrophy of overloaded adult rat muscle. Muscle Nerve 17:608-613, 1994

3. Phelan JN, Gonyea WJ. Effect of radiation on satellite cell activity and protein expression in overloaded mammalian skeletal muscle. Anat. Rec. 247:179-188, 1997

4. Schneider MR, Lahm H, Wu M, Hoeflich A, Wolf E. Transgenic mouse models for studying the functions of insulin-like growth factor-binding proteins. FASEB J 2000 Apr;14(5):629-40

http://www.hypertrophy-specific.com/...dex.html#art_1

Good post Laz.

We knew it was good but it sounds even better now.

so could one assume from this article that exogenous igf would be best used IM post workout for inj site increased growth?

Originally Posted by micksnowdog

so could one assume from this article that exogenous igf would be best used IM post workout for inj site increased growth?

correct into the muscle just trained post workout.

Originally Posted by Online Nutrition

correct into the muscle just trained post workout.

PWO IM injection = ouch.

Originally Posted by C_T

PWO IM injection = ouch.

yeah it doesn't sound very good and im sure it probably hurts like hell but thats suppose to be the best way.

Lets be serious tho.

The substance goes into the muscle, which simply is a slower rate of releasing into the bloodstream, where it gets transported to every cell in the body.

Your blood ships nutrients/oxygen, the works to the muscle.

So igf in your blood = igf in your muscle.

The benefits of PWO IM injection would not be as pronounced as you'd think.

I know what your saying but then we also have to think without really knowing the answer to the question purely speculation:
If a muscle is damaged from weight training and the cells are requesting IGF1 from the muscle in order to grow wouldn't injecting IGF1 into or close to the area in need of regeneration help to absorb where it needs/wants to go for muscle repairs. Sort of like the door is open come on in.

The second point is we dont know the answer we just base this theory on what other bodybuilders have done with no real science to back it up IM or subQ may very well have the same muscle building effect, the IM injections may very well be site swelling form the injection.

IFBB PRO MASTER OF THE UNIVERSE says "IM your IGF1 its the best" he gets 1000's of followers "hey your right mr pro master of the universe."

BUT is it site growth or is it swelling from the injection??....who know's, it's hard as fuck to obtain the real stuff now days anyway so i wouldn't even bother, the chinese stuff is also bunk as shit it's just as use full as icing on a cake, personally i'd rather use insulin it's cheap is way more effective and its always easy to obtain.....and AAA+++ it's the most anabolic hormone in the body.


I say fuck IGF costs Vs results it suck balls.
Do you ever hear of anyone who is already at a decent muscle mass go "man i used the IGF shit and bam 10kg's later im loving the stuff"????

All i ever here that rings true is "i used insulin on/off and HGH at decent dosages long term and well you guessed it i put on quality muscle with small aditions of gear"

I'd also base a majoity of those gains in the solid cycle purely on the insulin, its the main component driving nutrients into the muscles causing protein and glycogen levels to be well above normal. Think about it if you can maintain a larger amount of glycogen and protein in a muscle more often it has no choice but to adapt.
The skinny kid in school with no muscle's is still skinny with no muscles yet the fat kid who ate to much is still as strong as he was, he always ate his food increasing protein and glycogen retention causing muscle growth if he added weight training stimulus he is now even bigger and stronger, if the skinny kid adds weight training but doesn't increase protein and glycogen retention he will remain skinny, it's like all the newbies on forums saying why can't i get my body weight above 65kg?....why?? your not eating enough go eat everything then eat some more!

well my theory would be;

1. working a muscle group, draws blood into that muscle.

2. raising igf-1 levels in the blood prior to workout, then working that muscle will draw in alot of high igf-1 blood is pooling in that muscle.

Now, lets say a different theory;

1. working out a muscle group, which pumps the muscle full of blood.

2. PWO IM injection. What happens here is a substance is injected, basically what it does is it finds the closest bloodstream pathway and starts seeping into it, mixing with the blood.

Now, considering these 2 theory's, which method do you think, overall, has the highest concentration of igf-1?

Me personally, i think the first method. Using our blood system to deliver the substance. Because site injections are bullshit unless your injecting about 7 different spots all through the belly of the muscle. Its the larger arteries that spread the blood to the muscle, the idea of IM injection is to miss these parts.

So really, the igf is not being absorbed by the muscle its being injected into. I think this fact is false. To my knowledge it just doesn't make sense. You will have a large amount of igf-1 in a localised spot in the muscle that isn't getting much blood or nutrients. And over the course of about 2hrs, this is seeping into our bloodstream where its no-longer localised and is reaching every cell in our body.

Originally Posted by C_T

PWO IM injection = ouch.

Shooting IGF doesn't hurt. Your shooting with a slin pin.

S

Originally Posted by spearman

Shooting IGF doesn't hurt. Your shooting with a slin pin.

S

IGF1 LR3 should be mixed with 100Mm of Acetic acid per ml so that's 0.6% acetic acid, not much your thinking but it fucking stings like a bee subQ or IM.

i hear drawing BAC water into the slin pin with the AA igf combo helps a lot

I've used it alot in the past. You get a slight sting, but it really doesn't hurt.