It’s one of the most frustrating experiences in fitness. You follow a training program to the letter, eat well, and try to get enough sleep, but your results just don’t match up to the person next to you in the gym. They’re packing on muscle and hitting new personal records, while your progress feels painstakingly slow. It’s easy to fall into the trap of thinking, “Maybe I’m just a ‘non-responder’ to training.”
This feeling taps into a core part of our ancestral mismatch. We live in a world of standardized programs and one-size-fits-all solutions, but our bodies are anything but standard. We all have unique genetic blueprints that dictate how we respond to food, stress, and, yes, exercise. For years, the fitness world has used labels like “hard-gainer,” “responder,” and “non-responder” to explain these differences. But what if those labels are wrong?
A groundbreaking new study reviewed in the January 2026 issue of Monthly Applications in Strength Sport (MASS) challenges this entire framework. The research suggests that while our responses to training are deeply individual, the idea of a true “non-responder” might just be a myth. [1]
The Big Question Is Your Response to Training Just Luck?
To figure out if training response is a stable individual trait or just random chance, researchers designed a clever study. Instead of just one training block, they had participants complete two 10-week resistance training programs separated by a 10-week break (detraining period). [1]
This design is a major upgrade because it filters out the “noise” of everyday life. A single training block can be influenced by a bad month of sleep, a stressful period at work, or a temporary change in diet. By repeating the training, researchers could see if an individual’s response was consistent over time.
What the Science Says Your Response is Real and Repeatable
The results were remarkably clear: an individual’s response to training is highly repeatable.
People who gained a lot of muscle and strength in the first training block also gained a lot in the second. And those who gained little in the first block also gained little in the second. This shows that your response to a given training program isn’t just a fluke—it’s a predictable, individual characteristic. Some people are simply more prone to muscle growth from a given stimulus than others.
But here’s the crucial part that turns the “non-responder” idea on its head.
The Myth of the “Non-Responder”
While the magnitude of response varied, the study also showed that it’s incredibly unlikely for someone to have zero response, especially if the training dose is sufficient. As the author of the MASS review, Eric Trexler, points out, after the second training block—representing a double dose of cumulative training—almost everyone had gained muscle. [1]
This leads to a powerful conclusion: being a “non-responder” is likely a matter of dose and time, not a permanent state.
If you’re not seeing results, it’s probably not because your body is incapable of changing. It’s far more likely that you haven’t found the right training dose (a combination of volume, intensity, and frequency) or you haven’t stuck with it for long enough. This supports earlier research which found that athletes initially labeled as “non-responders” to aerobic training did, in fact, respond when the training dose was increased. [2]
The “Double-Edged Sword” of Being a High Responder
Interestingly, the study found a fascinating trade-off. The same individuals who gained muscle and strength the fastest also tended to lose it the fastest during the 10-week detraining period. [1]
This is a classic “double-edged sword” that mirrors other areas of human biology, like the “thrifty” and “spendthrift” metabolic phenotypes. [3] Some bodies are quick to adapt and quick to let go, while others are slower to change but more resilient at holding onto their gains. It’s a powerful reminder that there’s no single “best” way to be—just different strategies for adaptation.
The chart below shows the individual responses for muscle growth in the leg (VLCSA) and arm (BBCSA). Each line represents an individual participant in the study. As you can see everyone increased muscle size in both the arm and leg during training periods (RT1 and RT2). Now sure some grew more muscle than others, in some cases some grew A LOT more muscle than others, but EVERYONE added muscle. The same is true during the detraining period (DT), EVERYONE lost muscle, some more than others.
Practical Takeaways What This Means For Your Training At The Gym
This research is empowering. It moves us away from fixed labels and toward a more flexible, personalized understanding of training. Here’s how you can apply these findings:
- Patience and Consistency Are Your Superpowers. If you feel like a “low responder,” the answer isn’t to give up. It’s to give your body more time with the stimulus or to strategically increase the dose. Progress might be slower, but it is not impossible.
- Stop the Comparison Game. Your journey is your own. Your individual response rate is real and part of your unique biology. Comparing your progress to a high responder is like comparing apples and oranges—it’s a recipe for frustration and serves no purpose.
- Reframe “Non-Response” as a Signal. Instead of seeing a lack of progress as a failure, view it as a signal from your body that it needs more time to respond. It’s a call to adjust your training dose or have more patience, not to throw in the towel. It’s a problem to be solved, not a life sentence.
- Recognize the Value of Personalized Coaching. This is where the art and science of coaching come together. A good coach can help you navigate your individual response, find the right training dose for your body and your life, and make adjustments when you hit a plateau. They can help you solve the puzzle of your own physiology.
The Bottom Line
Your body is not broken.
You are not a “non-responder.”
You are an individual, and your response to training is a unique and repeatable part of who you are. While some may build muscle more quickly, the evidence strongly suggests that virtually everyone can make meaningful progress with the right dose of training applied consistently over time.
So, the next time you feel discouraged, remember this: you are a responder. You just need to find the right conversation to have with your body.
References
[1] Räntilä, A., Halonen, E. J., Tiainen, E. J., Kaasinen, S. O., Hulmi, J. J., & Ahtiainen, J. P. (2025). Repeated Resistance Training Reveals the Reproducibility of Muscle Strength and Size Responses Within Individuals. European Journal of Sport Science, 25(12), e70095.
[2] Montero, D., & Lundby, C. (2017). Refuting the myth of non-response to exercise training: ‘non-responders’ do respond to higher dose of training. The Journal of Physiology, 595(11), 3377–3387.
[3] Hollstein, T., & Piaggi, P. (2023). How can we assess “thrifty” and “spendthrift” phenotypes? Current Opinion in Clinical Nutrition and Metabolic Care, 26(5), 409–416.