If you have been training consistently but your muscles are growing more slowly than someone else’s, does that make you a non-responder?

A slow response over one training block cannot establish that your muscles are incapable of growing. It describes an outcome under particular conditions: the exercises you performed, the training dose, the period you measured, and the method used to measure it. Before treating that result as a biological identity, we need to separate those conditions from the person.

There are genuine differences in how people adapt to resistance training. But the difference between two before-and-after measurements is not a direct reading of genetic potential. The useful question is whether the result is reliable, whether the training was appropriate, and what can reasonably be changed.

What the muscle biopsies actually showed

A study by Christopher Mobley and colleagues provides a ...