Prevailing wisdom suggests that having more testosterone leads to more muscle and strength gain. After all, the hormone is synonymous with manliness, physical development, and vitality, so it only makes sense.

But are these common beliefs completely accurate, or is the truth somewhere else? Let’s talk about it.

What is Testosterone And How Does it Work?

Testosterone is a hormone––think of it as a small messenger running around your body, giving orders to specific cells. In men, testosterone is mainly produced in the testicles. In women, it’s made in the ovaries, albeit in smaller amounts.

Put simply, testosterone plays a huge role in many areas that affect your physical performance and overall fitness: muscular development, strength and power output, fat loss, and more.

Let’s look at muscle growth as an example. Unlike some hormones, testosterone can enter cells and convert to DHT thanks to an enzyme called 5α-reductase. DHT molecules then bind to androgen receptors, leading to large changes in the body.

One function of the hormone is to affect genes related to muscle hypertrophy. As a result, the hormone can promote muscle gain by positively impacting processes involved in physical development:

• Improving force production, leading to better performance and high-quality workouts
• Promoting muscle repair following a demanding workout
• Slowing down muscle protein breakdown
• Activating satellite cells, which can improve the capacity for muscle protein synthesis

Do Testosterone Levels Influence Muscle Growth?

In short, yes. However, the relationship doesn’t appear to be nearly as dose-dependent as most people think.

When comparing people with low testosterone levels and those who enjoy extremely high levels of the hormone as the result of ‘supplementation,’ there is a clear difference in muscle and strength gain, fat loss, and overall well-being.

Take, for instance, in this study from 1996, researchers split 43 people into four groups:

• Placebo + no exercise
• Testosterone injections + no exercise
• Placebo + exercise
• Testosterone injections + exercise

Another study from 2001 clearly shows a dose-dependent relationship between increases in testosterone levels via exogenous administration (in men receiving 25, 300, or 600 mg of testosterone weekly) and physical improvements (muscle and strength gain, fat loss, etc.).

But here is the thing:

According to research, high doses of exogenous testosterone appear beneficial because they increase androgen receptor density. One likely explanation is that the body produces more of these receptors, allowing testosterone to interact with the body and cause the necessary changes.

In other words, this is simply a way for the body to meet the greater testosterone demands that result from injecting the hormone and raising its levels beyond the physiological range.

The problem is that we might not notice the same thing if we increase testosterone levels within the physiological range.

But What About Within the Physiological Range?

Everyone wants to increase their testosterone levels, which is why testosterone ‘boosting’ supplements are so popular today. They promise to naturally boost levels of the hormone, thus leading to greater muscle and strength gains.

However, can we expect to notice a difference if our testosterone goes from, say, 400 to 800 ng/dL? After all, that’s a two-fold increase.

Let’s look at some data. In this study by McCall and colleagues, 11 college-aged men completed 12 weeks of high-volume training (33 total sessions). At the end of the experiment, the subjects had seen decent increases in bicep muscle size.

Subjects’ resting testosterone levels didn’t change; average levels were 518 ng/dL. Levels of the hormone varied by 172 ng/dL, meaning some subjects had testosterone levels of around 346 ng/dL, and others had levels of 690 ng/dL, or two times higher.

Yet, despite these differences, there didn’t seem to be a direct relationship between testosterone levels and hypertrophy. All the subjects saw similar gains despite the significant differences in test levels among some of them.

In a more recent study, researchers recruited 49 trained men and had them do full-body training four days per week for three months. Their findings?

We performed backward elimination and principal component regression on a relatively large cohort (n = 49) of resistance-trained men and conclude that the post-exercise AUC (i.e., acute transient net hormonal exposure) and resting hormone concentrations measured in the blood do not share common variance with RET-induced changes in muscle mass.

In other words, hormone levels (free and total testosterone, cortisol, etc.) were not correlated with muscle growth.

What Does This Mean For You?

Here are some key takeaways:

1. Don’t obsess over testosterone levels. While necessary for good health, well-being, and muscle gain, the relationship between gains and testosterone isn’t as linear as one might think.

The human body complex and numerous factors affect our training outcomes. So long as your test levels are not below the lower end of the spectrum (in other words, they are at least 300 ng/dL) and you’re not experiencing persistent symptoms of hypogonadism (low to non-existent sex drive, chronic fatigue, mood swings, etc.), you should focus elsewhere.

2. Pay attention to your nutrition. A balanced diet is crucial for optimal growth. Make sure you’re eating:

• Enough calories - a slight surplus (100 to 200 over maintenance) is generally best for bulking to build muscle
• Protein to support growth and recovery (at least 0.7 grams per lb)
• Carbs to support protein synthesis and promote optimal performance
• Dietary fats (0.35 to 0.45 grams per lb) to optimize hormone levels

3. Get enough sleep. Aim for at least seven hours of uninterrupted, restful sleep each night to feel better and maintain long-term motivation for hard and consistent training.

4. Follow a structured training plan. Design a workout plan that aligns with your goals and pushes you hard enough to see small, steady improvements. Random workouts here and there just won’t cut it.

5. Train hard. Aside from following a solid workout plan, push yourself enough on each set. For growth, that generally means training to an RPE of 7 to 8. In other words, you should leave two to three sets in the tank at the end of most sets.

In a nutshell, while testosterone is essential for growth, it’s not the end-all-be-all. Don’t ignore other aspects of fitness, and don’t conclude that you’re doomed to stay small just because you think your testosterone levels aren’t ‘optimal.’

Thanks for sticking around. I'll catch you next week!

Best,
Philip

All Newsletters ⇒