The same 12-week programme produces very different results — genetics explains 27.7%
In short
When 187 Asian adults completed an identical 12-week resistance training programme, lean body mass rose significantly across the cohort but varied enormously between individuals, with a coefficient of variation of 0.84. A genome-wide association study identified nine novel single-nucleotide polymorphisms associated with the change, and a genetic predisposition score built from them explained 27.7% of the variance — which also means roughly 72% lies outside the genome.
Running the same programme as someone else and watching them grow while you do not is a common experience. This study measured that spread directly. Divergent results from identical training is not an impression — it is a measured phenomenon.
How was it measured?
187 sedentary adults (51.3% female, mean age 21.5 ± 2 years) completed a supervised, periodised 12-week programme. The protocol was simple and tightly specified.
- Lifts — squats and bench presses
- Intensity — 70% of one-rep maximum
- Volume — 5 sets × 10 repetitions, 2 minutes rest between sets
- Frequency — twice weekly for 12 weeks
Lean body mass was quantified before and after with DEXA — dual-energy X-ray absorptiometry — rather than a tape measure or a bioimpedance scale, which is what makes these numbers trustworthy.
How large was the spread?
Across the cohort, lean body mass rose significantly. The distribution inside that average is the story. The change in lean body mass had a coefficient of variation of 0.84 — the standard deviation was 84% of the mean, meaning outcomes differed several-fold from person to person.
The genome-wide association study identified nine novel single-nucleotide polymorphisms significantly associated with the change. A weighted genetic predisposition score built from them explained 27.7% of the observed variance. One variant, rs10212396, sits near the ROBO2 locus, a gene potentially implicated in muscular adaptation — though the specific functional roles of most of the genes identified remain uncharacterised.
How should 27.7% be read?
The number cuts both ways. 27.7% is not small. It confirms that an inherited component of training response genuinely exists, and it is good grounds for not blaming yourself when someone else on the same plan grows faster.
It is also not everything. The remaining ~72% sits outside the genome: sets actually performed, protein and total calories, sleep, whether the twelve weeks were completed without gaps, and measurement error. Genetics changes the starting point and the slope, not the direction — the cohort as a whole gained significantly.
This cohort was untrained Asian adults averaging 21.5 years old. The population match is a strength for readers in that region, but the findings cannot be transferred directly to trained lifters or other age groups. It is also why commercial genetic tests promising to predict your training response remain poorly supported.
How this relates to your strength score
This study is a direct argument for why a relative score exists at all. Ranking by absolute load alone lets body size and inherited responsiveness decide much of the order, which is exactly what correcting for bodyweight, age and height is meant to reduce.
But correction cannot erase the coefficient of variation above. Which is why the most honest comparison is always yourself three months ago. More than a quarter of the gap between you and the person on the same programme was never produced by training. Use the ranking for motivation, and judge whether a programme is working by the slope of your own numbers.
As a bonus, the protocol itself is a good beginner template: squats and bench presses at 70% of 1RM, 5 × 10, twice a week — enough to produce significant lean mass gains across a whole cohort in twelve weeks. Pair it with getting started with a barbell.
Frequently asked questions
Why do people get different results from the same training?
Inherited differences in responsiveness are real. In a study where 187 adults completed an identical 12-week programme, the change in lean body mass had a coefficient of variation of 0.84, and a genetic score explained 27.7% of that individual variation.
Does genetics determine muscle growth?
It does not determine it. The genetic predisposition score explained 27.7% of individual variation, leaving roughly 72% outside the genome — volume actually performed, protein and calories, sleep, and completing the programme. The cohort as a whole still gained significantly.
What programme did the study use?
A supervised, periodised 12-week programme of squats and bench presses at 70% of one-rep maximum, 5 sets of 10 with 2 minutes rest, performed twice weekly. Lean body mass was measured by DEXA.
Can a genetic test predict your training response?
Not yet. This study was the first to identify these nine variants, and the specific functional roles of most of the genes involved remain uncharacterised. The cohort was also limited to untrained adults averaging 21.5 years old.
Is comparing yourself to others pointless then?
Ranking works as motivation but is a poor test of whether a programme is working. Since more than a quarter of the difference between two people on the same plan was never created by training, the change against your own numbers three months ago is the better measure.
Source: PubMed