Do Squats Make Your Arms Bigger?

Some say that working small muscle groups, such as the biceps and triceps, alongside larger muscle groups will make those muscles grow more quickly. 

You’ll often hear things like “to get big arms, you need to train your legs” or “deadlifts and squats make your whole body grow.”

The idea is based on research showing that heavy compound exercises lead to a post-exercise boost in various anabolic hormones, such as testosterone, growth hormone (GH), and insulin-like growth factor (IGF-1).

Train your arms at the same time as your legs, and your biceps and triceps will benefit from the high hormone levels flooding your system.

That’s the theory anyway. Personally, I’m not convinced.

In fact, most research fails to show that training the legs and arms together has any kind of meaningful impact on muscle growth over and above working the arms by themselves.

However, most research doesn’t mean all research, and there is some data out there to support the idea.

Scientists from Norway’s Lillehammer University College, for example, found that training legs immediately before working the biceps led to a faster rate of muscle growth compared to a biceps-only workout [1]. 

After 11 weeks of training, they saw greater gains in certain regions of the biceps in the high hormone condition. This suggests that the elevated hormones were responsible for the faster rate of muscle growth.

However, there are a number of weaknesses with this study that put the conclusions on shaky ground.

Here’s what Stuart Phillips — a Professor in the Department of Kinesiology at McMaster University — has to say in a letter to the editor of the European Journal of Applied Physiology:

“The findings are no more proof that systemic hormones exert an influence in the resistance exercise training-induced adaptations than any previous paper in this area. 

“It appears that selective reporting (considering only the site of the largest cross sectional area), incomplete statistical analysis (not comparing the changes in cross sectional area between arms), and questionable magnetic resonance imaging practices are the main messages from this paper.“

What’s more, these are the results from just one study. You can’t come to a strong conclusion on anything based on the results of one study. 

In fact, most research shows that training the biceps in a high hormonal environment doesn’t make them grow any faster.

A team of scientists from New Zealand got two groups of men to train their biceps twice a week for 10 weeks [2]. 

• Group one trained the biceps alone
• Group two did the same exercises as part of a full-body workout.

The full-body workout included exercises for the upper and lower body, such as the leg press, leg curl, lunge, bench press and dumbbell pullover.

The size of the biceps increased in both groups. But there was no significant difference in gains between the biceps-only and the biceps + full-body workout groups.

A similar trial looked at muscle growth in a group of men who trained their biceps for 15 weeks on separate days and under different hormonal conditions [3].

In the low hormone condition, subjects trained the biceps on one side of their body. On a separate day, they did the same exercise for the other arm, which was followed immediately by several leg exercises designed to boost the release of testosterone, GH and IGF-1.

In essence, the researchers were able to manipulate hormone levels so that, during the post-exercise period, one arm was repeatedly exposed to marked increases in testosterone, GH, and IGF-1 levels. The other arm was exposed to much lower levels of these hormones.

Because one arm of the subjects served as a control, both conditions also had the same genetic environment.

If the hormonal response to exercise was as important as some say it is, you’d expect to see the arm that was trained along with the legs and exposed to higher hormone levels grow more quickly.

But that isn’t what happened.

The size of the biceps increased to a similar extent in both groups — 12% in the low hormone condition versus 10% in the high hormone condition.

Strength also increased in both arms, but the increase was not different between the low hormone and high hormone conditions.

To quote the researchers directly:

“These findings, combined with our previous work, provide multiple lines of evidence that exercise-induced elevations of purportedly anabolic hormones are not necessary for, and do not enhance, muscle anabolism in young men. Our data indicate that exercise-induced changes in concentrations of systemic hormones do not reflect the underlying processes of muscle protein accretion and cannot be used as a proxy marker of muscle hypertrophy.”

Bottom line?

Exercises like squats and deadlifts aren’t going to have any meaningful impact on the size of your biceps and triceps. If you want bigger arms, you’ll need to train your upper body directly.