Muscle Growth Myths: Why Pumps, Hormones, and “Metabolic Stress” Don’t Build Muscle
Key Takeaways
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The “muscle pump” feeling and short-term hormone spikes are muscle growth myths — they don’t actually cause muscle growth.
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The real driver of growth is mechanical tension, not hormones or lactic acid.
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To grow muscle, focus on consistent, progressive resistance training rather than chasing the pump.
Introduction
For years, gym folklore has spread all sorts of muscle growth myths — like the idea that getting a crazy pump, flooding your muscles with lactic acid, or triggering huge hormone spikes would somehow make you bigger.
But a new review from McMaster University has completely debunked those beliefs.
In Load-Induced Human Skeletal Muscle Hypertrophy: Mechanisms, Myths, and Misconceptions, published in the Journal of Sport and Health Science (Van Every, Lees, Wilson, Nippard, & Phillips, 2025), researchers broke down what truly builds muscle and what doesn’t. Their conclusion? The real secret isn’t a fancy supplement or a hormonal surge — it’s mechanical tension, the stress your muscles feel when you progressively lift heavier weights.
This new research matters because it clears away confusion, helping lifters focus on what really works while leaving muscle growth myths behind.
Review of the Literature: Debunking Common Muscle Growth Myths
Myth #1: The Muscle Pump Builds Muscle
One of the most popular muscle growth myths is that the tight, vascular “pump” during workouts equals more muscle. The truth? It’s just temporary fluid buildup.
The review showed that this “pump” doesn’t lead to long-term gains. It’s mostly blood and fluid accumulating in your muscle, not new tissue being built.
Sure, the pump feels amazing — it’s motivating, and it can help you connect with your training — but it’s not a sign of permanent muscle growth. In other words, enjoy it, but don’t chase it.
Myth #2: Hormone Spikes Drive Muscle Growth
Another major muscle growth myth is that the bigger your testosterone or growth hormone spike after lifting, the more muscle you’ll build.
The study by Van Every and colleagues (2025) reviewed decades of evidence showing that short-term testosterone changes after a workout don’t translate into bigger muscles. In one experiment, participants trained both arms, but one arm was exposed to much higher post-workout hormone levels. After 15 weeks, both arms grew equally.
Even more surprising? Men and women build muscle at similar rates relative to their size, despite men having 10–20 times more testosterone. That’s proof that natural hormonal differences don’t control your results — training effort does.
Myth #3: Lactic Acid and “Metabolic Stress” Cause Hypertrophy
Feeling the “burn” has been romanticized as a sign of progress. But according to the research, this is another muscle growth myth.
Metabolic stress — the buildup of lactic acid and fatigue — doesn’t directly cause muscle fibers to grow. What it does do is make your body recruit more muscle fibers to keep moving when you’re tired. That’s helpful, but it’s the tension those fibers experience, not the burn itself, that triggers growth.
Even methods like blood flow restriction training (BFR), which purposely create more metabolic stress, don’t grow muscle faster unless they also create sufficient mechanical tension.
Results: The Science Behind True Muscle Growth
After analyzing dozens of studies, the researchers concluded that mechanical tension — the force your muscles generate when working against resistance — is the real foundation of muscle growth.
When you challenge your muscles through progressive overload (lifting heavier over time), special sensors inside the muscle activate protein-building pathways. This leads to thicker, stronger fibers — the actual structure of muscle growth.
On the flip side, factors like cell swelling, hormone spikes, and lactic acid showed little to no effect on stimulating these pathways. So while they might be part of the workout experience, they aren’t the reason your muscles grow.
The review also tackled the trend of “sarcoplasmic hypertrophy” — the idea that muscles can expand mostly through fluid or glycogen. The authors found that lasting growth comes from building more contractile proteins, not simply filling muscles with water or energy stores.
What This Means for Your Training
So what’s the real takeaway from all these busted muscle growth myths?
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The “pump” doesn’t equal progress.
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Hormone (i.e., testosterone) spikes aren’t magic.
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The “burn” isn’t a growth signal.
What works? Consistent, progressive training that makes your muscles generate tension. That’s what tells your body, “Hey, we need to adapt — let’s grow.”
You don’t need fancy supplements or extreme training tricks. Whether you’re lifting 100 pounds (about 45 kilograms) or 200 pounds (about 91 kilograms), what matters most is that you keep pushing close to your limits.
Practical Applications
Here’s how to apply this research in your workouts:
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Progressive Overload Wins
Gradually increase your weights, reps, or sets. That’s the simplest, most effective muscle-building strategy there is. -
Train Close to Failure
Those last few reps before you can’t lift anymore? That’s where growth happens. -
Don’t Chase the Pump
Enjoy the feeling, but know that it doesn’t cause hypertrophy. -
Rest Long Enough Between Sets
Take enough time to recover — at least 1.5 to 3 minutes — so you can lift heavy again. -
Be Patient and Consistent
On average, most people can gain 3–4 pounds (1.3–1.8 kilograms) of muscle over several months of proper training. That might not sound flashy, but it’s real progress. -
Ignore Fitness Fads
Any program promising to “hack” your hormones or “maximize the pump” is probably selling hype, not results.
FAQ: People Also Ask About Muscle Growth Myths
Q: Does the muscle pump actually build muscle?
No. The pump is just extra blood and fluid in your muscles. It feels great but doesn’t cause long-term growth (Van Every et al., 2025).
Q: Do testosterone or growth hormone spikes after workouts help muscle growth?
Not really. Short-term hormone spikes have no measurable effect on long-term muscle gains. What matters most is training volume and tension.
Q: Is “feeling the burn” important for building muscle?
The burn only signals fatigue, not growth. You can build muscle without ever feeling that intense burn, as long as your sets are challenging.
Q: What’s the number one cause of muscle growth?
Mechanical tension — progressively challenging your muscles with heavier loads over time.
Q: Can you grow muscle with light weights?
Yes — as long as you train close to failure. Low weights can still create enough mechanical tension to stimulate growth.
Conclusion
The pump, the burn, and the hormone spikes might make your workouts feel intense, but they aren’t what makes your muscles grow. Real growth happens when you apply mechanical tension, recover properly, and stay consistent.
Forget the hype. Lift hard. Rest well. Repeat. That’s how real muscle is built — no myths required.
References
Van Every, D. W., Lees, M. J., Wilson, B., Nippard, J., & Phillips, S. M. (2025). Load-induced human skeletal muscle hypertrophy: Mechanisms, myths, and misconceptions. Journal of Sport and Health Science, 101104. https://doi.org/10.1016/j.jshs.2025.101104
