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Physiological Elevation of Endogenous Hormones Results in Superior Strength Training Adaptations – Research Review

Rønnestad BR et. al. Physiological elevation of endogenous hormones results in superior strength training adaptation.  Eur J Appl Physiol. (2011) Feb 16.

The purpose of this study was to determine the influence of transiently elevated endogenous hormone concentrations during exercise on strength training adaptations. Nine subjects performed four unilateral strength training session per week on the elbow flexors for 11 weeks. During two of the weekly sessions, leg exercises were performed to acutely increase the systemic anabolic hormone concentration immediately before the exercises for one of the elbow flexors (L + A). On the two other weekly training sessions, the contralateral elbow flexors were trained without prior leg exercises (A). By randomizing one arm of the subjects to serve as a control and the other as experimental, both conditions have the same nutritional and genetic environment. Serum testosterone and growth hormone was significantly increased during the L – A training session, while no hormonal changes occurred in the A session. Both A and L + A increased 1RM in biceps curl, peak power in elbow flexors at 30 and 60% of 1RM, and muscle volume of the elbow flexors (p < 0.05). However, only L + A achieved increase in CSA at the part of the arm flexors with largest cross sectional area (p < 0.001), while no changes occurred in A. L + A had superior relative improvement in 1RM biceps curl and favorable muscle adaptations in elbow flexors compared to A (p < 0.05). In conclusion, performing leg exercises prior to arm exercises, and thereby increasing the levels of serum testosterone and growth hormone, induced superior strength training adaptations compared to arm training without acute elevation of hormones.


A long-held belief that has floated around the world of strength and hypertrophy training is that training legs (for a variety of reasons including hormonal) has a positive effect on either strength or size.  Many, many systems of training are based around that (including Dan John’s Mass Made Simple which I recently reviewed and others).

Previously I examined a paper that looked at this in a confusingly titled Casein Hydrolysate and Anabolic Hormones and Growth – Research Review (this was  a brief period when I was looking at two papers at once, it’s the second paper I reviewed) which, in a somewhat confusing study design found no impact of raising ‘ostensibly anabolic hormones’ (translation: testosterone and growth hormone) on size gains.

They concluded that the small hormonal pulses caused by leg training did not in fact affect growth in the arms.  I talked in some detail about a bunch of other issues related to the topic and I’d refer readers to that review rather than write it all again here.

However, a single paper (I’d note that the same group had done a second paper with identical results) isn’t the case closed answer to things; that’s not how science works.  And when another paper comes along with opposite conclusions, you have to look at all the data to see what’s going on.

Which is a, for me anyhow, fairly short introduction to today’s paper which, as you might imagine, looked at the same topic with (at least somewhat) different results.


The Paper

Eleven untrained male subjects were recruited, aged 20-34 years, none had performed any strength training in the previous 6 months.  Two subjects did not complete the study which means that only 9 did.  The study lasted a total of 11 weeks and weight training was carried out 4 days/week with the biceps being trained at every workout.

However, each arm was only trained twice/week.  For one of the arms, the biceps exercises were performed after the subjects had performed heavy leg training.  For the other arm, arms only was trained.  Subjects were informed to ‘keep the arms relaxed’ during the leg training although I doubt this happened; folks always hold on for dear life on heavy leg machine work.

This design confused some people (check the comments section) in the previous research review and I want to explain it.  Basically the study was allowing each subject to be his own control.  That is, for all 9 individuals who finished the study, each one trained one arm after heavy leg training and the other arm without heavy leg training. This way any differences in arm size or strength gains could be attributed to the performance (or not) of the leg training rather than just to being differences between individuals.

That is, say we took two people and had one of them train arms after legs and the only one train just arms.  Let’s say that the first guy made better gains. We wouldn’t be able to say if it was due to the leg training per se, or if it was just because he had better gains (maybe the first guy would have made better gains no matter what he did).  The study design used, having each subject be their own control avoids this confound.

The researchers measured both strength gains (for biceps and arms) with 1 repetition maximum (1RM) biceps curl, leg strength was measured as 1 repetition maximum leg press.  Peak power was also measured for the biceps at 30 and 60% of 1RM.  Muscle size changes were measured using magnetic resonance tomography to determine changes in muscle cross sectional area and 9 images were taken with the final 4 being used to determine changes in muscle size (this will make more sense in a second…maybe).

Hormone levels were measured to ensure that changes in testosterone and growth hormone had actually occurred during the leg training which consisted of leg press, leg extension and leg curl. The arm training consisted of warm-ups followed by 2 sets each of biceps curl, hammer curl and reverse curl. The training was marginally periodized and started with 3 sets of 10RM and 8RM with 60-90 seconds rest in weeks 1-5 and was adjusted to 8RM and 6RM for weeks 6-10.   This note will seem out of place but the subjects were told to ‘relax the arms while performing the leg exercises’.

In terms of strength, the leg press strength went up 23%.  For the arm trained alone, the strength gains was from 39.2 to 44.7kg over 11 weeks; for legs plus arms the gain was from 37.5 to 45.3 kg so the relative improvement was greater.  It’s worth mentioning that the legs plus arms ‘arm’ started out weaker meaning they had more room to improve.  But note that the end result was only 1kg difference in maximum strength; sure it’s 20% gain vs. 15% gain but the absolute amount and the end difference is still pretty irrelevant.  Peak power increased in both the arms only and legs+arms group with no difference between them.

But what about size?  Recall from above that the researchers took a bunch of sequential photos of the arm and then looked at the final 4 to look at size differences.  And here’s where it gets confusing.  The researchers found that the size gains for arms only vs. leg+arms were identical for the first 2 measured slices but that the legs+arms group had larger gains in the last two (furthest away) slices.  I know, this doesn’t make any sense, here’s the chart.

That's so weird....
That’s so weird….


What you can see is that for Section 6 and 7, both groups made identical gains.  For sections 8 and 9 the legs+arm arm made gains and the arms only group did not.  And the results of all of this is colored by the error bars which are almost as large as the difference between groups.  I have no clue about sections 1-5 which were not reported on.

The researchers state that “ANOVA analyses revealed that both groups increased the CSA of the two proximal sections, while only L+A increased the elbow flexors’ CSA at the two middle sections, where the CSA of th elbow flexors was largest.”  Essentially, the belly of the biceps is where the difference was seen.


My Comments

Ok, so now we have two disagreeing papers, what’s going on?    In the study described in Casein Hydrolysate and Anabolic Hormones and Growth – Research Review, training legs with arms had no impact on size gains.  In this study, there was a difference although an odd one (only part of the arm showed a differential growth) with a very very slight difference gain in strength although this is confounded by the legs+arm group ‘arm’ starting weaker.  Sure they made better relative gains but they also had more room to improve.  And although the legs+arm ‘arm’ ended up a bit stronger, the difference was a stunning 1kg (2.2 lbs) stronger.  Yippee.

First, how do we explain the discrepancy between studies?  I mean other than just dismissing whichever study you don’t agree with.

The researchers suggest that the main difference in results is in the timing of the exercises.  In the first study on the topic, the leg training was done AFTER the arm training while in this paper the leg training was done BEFORE the arm training and perhaps anabolic hormones need to be increased prior to the arm training to have an impact.  This would require further study.  Basically they’d need to repeat the study and have one group do legs + arms with legs first and the other legs+arms with leg training second to see if timing was the difference.

Regarding the rather odd regional difference in growth, the researchers simply state “..the finding of no statistical significant increase in CSA at the part of the elbow flexors with the largest CSA in A was not expected and the reasons remain unknown.”  Science speak for “I dunno.”

Here’s my actual random-assed guess.  Recall from above how subjects were told to ‘keep the arms relaxed’ during the leg training.  Have you ever seen anybody actually do it on heavy leg machine training?  Me neither.  Invariably they hold on to the machine handles with a death grip and I am willing to semi-seriously argue that the legs+arms group got a better direct arm training stimulus from the isometric work.  Please note the phrase ‘semi-seriously’ and don’t get all freaked in the comments on this one.

So what’s the conclusion of all of this?  Honestly, I’m not sure.  The difference in strength gains was minimal and I can’t make any more sense of the size gains, especially the weird differential size gains seen in different ‘parts’ of the biceps, than the researchers did.  Small group size, measurement error, just variability in all of this.  I’m sure at least one person will argue that ‘If they’d squatted like real men, there would have been a difference’ in the comments section.

Maybe a longer study would show more pronounced results.   There’s just no way to tell.   Frankly, given the exceedingly small differences in anything measured I find it hard to use this study to support the long-held idea that training legs has a systemic anabolic effect.

It is interesting to note that the subjects reported generalized fatigue during the arm training following the heavy leg work and this is a practical consideration that people tend to miss I think.  If the goal is increased upper body strength or size, training heavy legs first often takes so much out of the person that the upper body training is compromised.  Sometimes severely.

Anybody who has done the classic 20-rep squat routine can attest this, you’re usually cooked after the squat set which means compromised upper body work.  And if you want to use this study as support for the impact of leg training, you can’t say “Just train legs last” because timing may matter.

As usually I think it comes down to priorities; if your goal is optimal upper body training, tiring yourself out first with heavy leg training would seem to have as many cons as pros.  Even if the hormonal effect is improving overall gains, the impact (at least based on this study’s results) would appear to be tiny at best.

And I realize that I’m finishing up this research review without much of a conclusion.  But this paper has been making the rounds to ‘prove’ the old idea of training legs to improve upper body growth.  Certainly it adds to the body of literature (we now have two studies showing no impact of leg training on arm growth and one study showing a small effect with the difference appearing to be when legs were trained).  But too many guys have gotten huge upper bodies (go to any weight room) without ever training legs for the argument that leg training is required to make much sense.

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