“Why are we squatting? I want bigger arms.”
“Well, if you do heavy lifts for your legs, you will produce a greater base of anabolic hormones to work off of later and that will allow you to build bigger arms.”
As a personal trainer in Schaumburg, I swear I have had this conversation with almost all of my male clients at some point in time. Unfortunately, the advice I gave is dead wrong. Check out why in my review of literature for this study!
In the lay fitness world it is often said that performing exercises that increase anabolic hormone levels will increase hypertrophy everywhere throughout the body (2).
It is shown that exercise can acutely increase anabolic hormone levels (3, 4, 8, 9). Additionally, it is shown that exercise can increase muscle protein synthesis (MPS) and intracellular signalling proteins (5, 6, 7). However, it has yet to be shown that an increase in anabolic hormone levels leads to a concomitant increase in either MPS or the phosphorylation of intracellular signalling proteins.
The aim of this study is to determine whether an increase in anabolic hormone levels after exercise leads to an increase in MPS and intracellular signalling proteins in tissues that were not challenged during the exercise (1). The authors hypothesized that an increase in anabolic hormone levels would lead to an increase in both MPS and the intracellular signalling proteins (1).
Eight healthy men aged 20 ± 1.1 years participated in the study. The participants didn’t have any formal weight training experience. They also had not consistently partaken in weight training during the previous year.
Immediately before exercise, participants were infused with l-[ring-13C6]phenylalanine. This was done so the participants had amino acids that were available during the MPS process.
The participants performed biceps curls unilaterally on one day. This was the “Low Hormone” (LH) day. On another day the participants performed the same volume of biceps curls using the contralateral arm. These curls were followed by multiple leg exercises designed to acutely increase anabolic hormone levels. This was the “High Hormone” (HH) day.
Muscle biopsies were taken from the involved biceps of the participants after both of the exercise days. These were analyzed for intracellular signaling proteins. Western blots were used for this analysis. One factor ANOVAs were used for the statistical analysis.
Blood samples were taken at baseline and at the end of each of the exercise days. These samples were analyzed for lactate, glucose, insulin, cortisol, testosterone, growth hormone (GH), and insulin-like growth factor 1 (IGF-1) levels. Two-factor repeated measures ANOVAs were used for this statistical analysis.
All of the anabolic hormones were at their highest levels 15 minutes after completing the HH exercise. Except for cortisol, all of these levels returned to the baseline levels within 60 minutes of completing the HH exercise. Cortisol returned to the baseline level by 120 minutes after the HH exercise.
There was no difference in the amount of MPS in the biceps brachii tissue between the LH day and the HH day.
The phosphorylation of STAT3 and p70S6K were elevated after both exercise days, but there was not an additive effect of the anabolic hormones. The other signalling proteins were either unchanged after the different exercise days or slightly decreased after the HH day.
Other Literature Findings
MPS is elevated for up to 36 hours after exercise (5, 6, 7). IGF-1 levels are also elevated for up to 24 hours (8). GH returns to resting levels two hours after exercise and testosterone returns one hour after exercise. (8, 9).
There are conflicting opinions in the research regarding the mechanism of MPS. While some research cites the availability of amino acids as the mechanism of MPS (14), other research finds insulin to be the stimulatory agent (15). By the same token, other research has found insulin to prevent protein breakdown instead of stimulate MPS (16).
More recent research cites the contraction of a muscle as the mechanism that begins the process of MPS (17). Following contraction, phosphorylation of mTORC1 occurs (17). This begins a series of biochemical reactions that ultimately leads to the phosphorylation of rpS6, which is said to both increase the size of cells as well as the proliferation of cells (17).
This study contradicts much of what is said in the lay fitness world (2).
There are three important takeaways from this study. The first is that the acute increase in anabolic hormone levels does not increase muscle protein synthesis. A concept that is often described in fitness magazines and blogs is that by performing exercises that increase anabolic hormone levels, hypertrophy of tissues that were not challenged will occur at a greater rate (2). This study shows that it is highly probable that this claim is false.
The second important takeaway from this study also contradicts the lay conversation. An idea often thrown around the traditional gym environment is that the spike in anabolic hormones from exercise carries over from one day to the next. What this study shows is that anabolic hormones return to resting levels within 60-120 minutes after completion of the exercise.
The third important takeaway is that in order for a tissue to hypertrophy it has to be challenged directly. This means that if somebody wants bigger biceps, they have to challenge their elbow flexor system.
One application of this study is in regards to exercise design. Understanding that a tissue has to be challenged in order for MPS to occur within that tissue may lead to more appropriate exercise design. If this information is not understood, an appropriate challenge may not be created.
Another application of this study is to aid in the defense against the misinformation circulating among the lay regarding muscle hypertrophy. Understanding the conditions by which muscle hypertrophy occurs will allow for more intelligent training and discourse on the subject.
— End original review —
Ultimately, whatever area of your muscular system you want change must be challenged directly. While squatting may be a wonderful exercise to challenge your glutes, hamstrings, and quadriceps, it does not seem plausible that it will actually help to grow your arms.
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