Individualizing Your Training Without Inventing
Introduction
"Every body is different" is one of those phrases that's true and almost always used to justify the opposite of what it means. It serves to dismiss recommendations you don't like, to sell personalized protocols with no basis, and to avoid following any plan for more than a month.
Individualization exists and is real. But it's smaller, more specific and more boring than the word suggests.
You are different. What you aren't is different enough to need another physics.
What barely varies
Worth starting here, because this is where individualization gets misused.
The basic principles apply to everyone: muscle grows with mechanical tension and progressive overload; strength improves by practising the movement under heavy load; endurance improves by accumulating volume; nobody adapts without recovering. There are no bodies that respond in reverse.
Nor is there a body that gains muscle without eating enough, or one that progresses without increasing the demand. When someone says "that doesn't work for me", what's usually behind it is an execution different from the one they believe they're doing.
The responder trap
Here's a finding that changed how this topic is understood, and that has barely reached the public.
You commonly read that "responders" and "non-responders" exist: people who improve a lot and others hardly at all on the same program. Studies do show that spread.
The problem is that much of that spread isn't real individual variability: it's noise. Measurement error, day-to-day variation, chance. Atkinson and Batterham made the point clearly: to claim genuine between-person variability you need a specific design — measuring the same person repeatedly, or including a control group — and most studies don't have one.
When those designs are used, real individual variability shrinks considerably and in several cases nearly disappears. In other words: you're less special than the graph suggests.
This has a direct practical consequence: before concluding a method doesn't work for you, rule out that you simply didn't run it long enough or measure it properly.
What does vary, and deserves adjusting
That said, real differences exist and it's worth knowing which ones, because those are the ones worth attending to.
Recovery capacity. Varies with age, sleep, stress, physical work and genetics. It's probably the most important individual difference, and it determines how much volume you can sustain.
Anatomy. Femur and torso length change which squat variation suits you. Shoulder and hip mobility change which grips and ranges are comfortable. That isn't preference: it's leverage.
Injury history. Determines what to avoid and what to reinforce, and it's one of the few things that justifies deviating from a standard plan.
Preferences. They look frivolous and aren't: adherence rules, and doing exercises you hate is an efficient way to quit. Between two equivalent options, the one you enjoy is objectively better.
Context. Schedule, equipment, distance to the gym, children. It determines a real plan more than anything else and appears least in published programs.
Response to frequency and to failure. Some people tolerate training near failure often; others accumulate fatigue fast. You find this out by testing, not by reading.
The rule: individualize the how, not the what
This is the criterion that organizes everything above.
The what is common: movement patterns, progressive overload, sufficient volume, adequate protein, rest.
The how is yours: which variation of each pattern, how many days, at what time, with what equipment, how close to failure, at what rate you progress.
When someone "individualizes" by removing progressive overload or leg training, they aren't individualizing: they're avoiding.
How to discover your real differences
1. Change one thing at a time. Change three and you won't know which one worked. 2. Give it twelve weeks. Less than that can't separate signal from noise. 3. Measure before and after, with the same method. Without a log there's no possible conclusion. 4. Repeat the experiment. One result can be coincidence; two start to be information. 5. Note how it felt, too. Tolerance to a method is legitimate data, not an excuse.
Common mistakes
Using individuality to dismiss the uncomfortable. "My legs just don't respond" rarely survives a look at the log.
Concluding after three weeks. The most common period for quitting is also the one that yields the least information.
Confusing preference with efficacy. Enjoying an exercise doesn't make it superior; it makes it more likely, which is plenty.
Copying someone else's individualization. The plan of someone with your same goal may be tuned to an anatomy and a schedule that aren't yours.
Looking for a test that settles it. Commercial genetic tests for exercise response have no support for guiding training decisions.
Conclusion
Real individualization is a second-order adjustment on top of common principles: the what is shared, the how is yours. And much of what looks like individual difference turns out, measured rigorously, to be noise.
Do this before your next change of plan: pick one variable you suspect works differently in you — frequency, proximity to failure, volume — and test it for twelve weeks with a log, changing nothing else. It's slow, and it's the only way to learn something real about yourself instead of repeating a hunch.
References
- Atkinson, G., & Batterham, A. M. (2015). True and false interindividual differences in the physiological response to an intervention. Experimental Physiology, 100(6).
- Hecksteden, A., et al. (2015). Individual response to exercise training: A statistical perspective. Journal of Applied Physiology, 118(12).
- Hecksteden, A., et al. (2018). Repeated testing for the assessment of individual response to exercise training. Journal of Applied Physiology, 124(6).
- Barbosa-Silva, J., et al. (2021). Is there interindividual variability in response to resistance training? A systematic review. Journal of Strength and Conditioning Research.
- Pickering, C., & Kiely, J. (2019). Do non-responders to exercise exist — and if so, what should we do about them? Sports Medicine, 49(1).