If you’ve been in the fitness world for a while, you’ve probably heard the debate: does bigger muscle size increase strength?

It seems logical — if your muscles grow, you should automatically be able to lift more weight, right? But a 2021 study by Buckner and colleagues challenges that assumption and reveals a much more nuanced answer.

In this article, I’ll break down the research, highlight key findings, and share what it means for your training program if you’re serious about getting stronger.

The Big Question: Size vs Strength

Over the past three to five years, fitness enthusiasts have hotly debated whether gaining muscle size (hypertrophy) directly boosts strength potential.

Think about it: if your biceps get bigger, do you automatically curl more weight?
Or is it more about how you train — your rep ranges, load selection, and program design — rather than just how large your muscles grow?

Spoiler alert: it’s a loaded question, and today’s research review helps shed some important light on it.

Study Overview: Buckner et al., 2021

The 2021 study, published in Clinical Physiology and Functional Imaging, aimed to examine the relationship between exercise-induced muscle hypertrophy and strength gains in resistance-trained individuals.

Specifically, the authors wanted to determine:

  • Does traditional hypertrophy training (higher reps, moderate weights) lead to better strength gains compared to just lifting heavy singles?

  • If you gain muscle size, does that provide a strength advantage later on?

In short: does bigger muscle size increase strength potential — especially in trained lifters?

Study Methods: How It Was Tested

To find out, researchers had 25 resistance-trained individuals perform bicep curls with each arm, but each arm followed a different training condition:

  • One arm: Four sets of 8–12 reps taken to failure (traditional hypertrophy training)

  • Other arm: Worked up to a heavy single (one-rep max training) each session

Both arms trained twice per week for 8 weeks.

Following this, participants entered a 4-week strength-focused mesocycle, where both arms trained identically — working up to a one-rep max during each session, with hypertrophy maintenance sets added.

Measurements:

  • Maximal 1RM biceps strength

  • Biceps muscle thickness (via B-mode ultrasound)
    These were assessed at baseline, after 8 weeks, and again after the 4-week strength phase.

Study Results: What Happened?

Here’s what the researchers found:

  1. Muscle growth:
    The traditional hypertrophy group (8–12 reps) experienced greater increases in muscle size compared to the 1RM-only training group.

  2. Strength gains:
    Despite the difference in muscle growth, strength gains were similar between both arms after the initial 8 weeks.

  3. No advantage from hypertrophy:
    Even after the 4-week strength phase, the bigger arms (from hypertrophy training) did not outperform the smaller arms in terms of strength.

  • The changes in muscle size were moderate, with the greatest gains at the 70% upper arm site.

  • Mean muscle thickness increase: 0.21 cm — a small, measurable change, but not enough to produce a strength advantage.

What This Means for You

1. Strength Is Not Just About Size

Despite traditional thinking — and what many textbooks suggest — strength adaptations are not solely dependent on muscle growth.

In this study, even trained lifters with years of experience were able to boost their strength without significant hypertrophy, suggesting other factors at play.

2. Neural Adaptations Matter

Practicing lifting heavy weights can strengthen your body through neural adaptations (like better motor unit recruitment and coordination) even when your muscles don’t visibly grow.

This might explain why focusing on low-rep, high-load training can produce strength gains without drastic size changes.

3. Bigger Muscles May Help — Over Time

While short-term gains in muscle size didn’t improve strength in this 12-week window, it’s still possible that longer-term hypertrophy (over 6–12 months) could play a more significant role in strength adaptations.

But if your primary goal is to get stronger fast?
You need to focus on training specifically for strength:

  • Heavy loads

  • Low reps

  • Practicing the actual lifts you’re trying to improve

Main Takeaway

If you want to get seriously strong, you have to train specifically for strength — not just chase bigger muscles.

Additional size might eventually contribute to performance, but it’s not the only factor (or even the biggest factor) when it comes to short-term strength gains.

In fact, the small muscle growth you might achieve over an 8-week training block is probably too small to make a meaningful impact on your ability to move heavier weights.

What Do You Think?

Have you ever gotten stronger without seeing big changes in muscle size?
Or maybe you’ve experienced size gains without an obvious strength boost?

I’d love to hear your experience — drop a comment below and let’s talk about it!

If you found this article helpful, make sure to check out more evidence-based fitness tips right here each week. 🏋️‍♂️

🔗 Related reading:
Want to focus on growing muscle size the smart way? Check out my evidence-based hypertrophy training tips here — packed with practical strategies you can apply in your next training block.