Friday, October 14, 2011

Differences in Growth Hormone, Insulin and IGF-1 Response in Trained and Untrained Resistance Trainees - Further Evidence That GH Builds Neither Muscle Nor Strength

Image 1: Rookie (top) or veteran (bottom, Jack Lalanne), their hormonal response to push-ups is different, but does not explain the different outcomes of strength training.
If you are a regular, here at the SuppVersity, you will have hear me lament the fact that in many of the mainstream studies on the effects of exercise on body composition, endocrine parameters and so on, the study participants are either sickly, obese or both... admittedly, whenever measures of muscle hypertrophy are involved, the subjects are usually healthy rookies, which is by  no means better, as you all know from your first weeks in the gym that, despite doing everything wrong, your strength and size gains were tremendous. Now, the obvious question is, are the endocrine adaptations / responses distinct, as well? According to the results of a recent study by Rasani Ranjbar et al. they are (Hasani-Ranjbar. 2011) - surprisingly, though, on paper, the endocrine milieu of the veterans appears more conducive to strength and size gains than that of the rookies... but let's take a look at the actual results, before we even start discussing their implications.

The Iranian scientists recruited 15 previously strength trained and 19 untrained male (how else could it be in this lovely country?) students at the Tarbiat Moallem University, divided them in an experimental (trained) and a control group and took blood samples at 10am (pre-test) after the students, who had arrived at the lab at 7am, had been served identical breakfasts (at 7:30-8:00am). Subsequently, the training groups (E1 = previous strength training experience; E2 = rookies) performed a resistance training protocol at 70-80% of their maximum strength in the 10-12rep range (i.e. a classical "hypertrophy training"), consisting of 4 sets of chest presses, stretch wires [I have no clue what kind of Iranian specialty that is], leg extensions and leg curls to failure with rest times of 2 minutes in between sets and 4 minutes between exercises.
Figure 1: Training induced changes in growth hormone (GH) compared to untrained control (Hasani-Ranjbar. 2011).

Blood was drawn at four timepoints: pre-test (T1), immediately after cessation of the exercise session and before lunch was served (T2), five hours post training (T3) and seven hours post training (T3). The samples were analyzed for growth hormone (GH), insulin, insulin-like-growth-factor 1 (IGF1), IGF1 binding protein 1 and 3 (IGFBP1 & IGFBP2). I have plotted the relevant data (i.e. data where you see meaningful changes) in figures 1 & 2.
Figure 2: Training induced changes in insulin and IGF1 compared to untrained control (Hasani-Ranjbar. 2011).
Now, what do we make of these results? Obviously the immediate GH response to resistance training is more profound in the veteran group, it is yet more sustained in the rookies, whose insulin levels interestingly skyrocket in the late post exercise period, yet in the absence of any significant increases in IGF1 levels (the same was true for the binding proteins) over the untrained control group.
Figure 1: Absolute IGF1 levels (in ng/ml) in trained and untrained rookies and veterans (Hasani-Ranjbar. 2011).
I don't know which data the Iranian scientists analyzed, but despite the fact that there is as they state a steady decline in IGF1 this probably isn't a result of the strength training regimen (as the Iranians would have it) but simply related to the lack of food intake in the 5-7h post lunch, which was ingested right after the post blood draw, i.e. exactly 5 hours before the 5h post blood was drawn....

Be that as it may, the more relevant result is that there may be differences in the endocrine response to exercise, but those are exactly contrary to what we would have to see, if the highly marketable GH increase, you are supposed to spike with all sorts of supplements had any effect on your gains in the gym. After all, you bet that if any of the two groups had had measurable strength or size increases at a subsequent training session / body composition measurement, it would have been the rookie group. That being said, this study further supports the position of the Phillips group from McMaster University (cf. Arms Don't Grow Faster with Prior Leg Training), who maintain that the exercise induced GH increase has absolutely no effect on strength or size gains... in other words, spending money on respective supps or focusing on training techniques that have been shown to increase GH (and have not been shown to be productive in terms of size and strength gains) is not advisable.