Why two people on the same programme progress differently

Two people join the gym the same week, run the same three-day programme, eat roughly the same and sleep roughly the same. Four months later one has added 15 kg to their bench and looks visibly different; the other has added 5 kg and looks much the same. The slower one's first thought is that they must be doing something wrong.

Usually the answer is: partly yes, partly no. Differences in how fast people respond to training are real and have been measured many times. They are also less dramatic than they look from the changing room, and a good share of what gets blamed on genetics comes from things that can be changed.

What is reliably known

The spread of responses to one programme is wide. The evidence here is consistent: put a large group on identical supervised training and the average gain is clear, but individual results fan out. Some people gain noticeably more muscle and strength than the average, some noticeably less. The same pattern shows up in strength work, in hypertrophy work and in endurance training.

Strength and muscle do not always move together. The same person can be below average at adding tissue and above average at adding kilos to the bar. Strength is substantially a learned skill: technique, coordination, and how well the nervous system recruits fibres at once. Two lifters with similar muscle gain can therefore post very different numbers.

The starting point explains a lot. An untrained person gains fastest in the first six to twelve months, then the curve flattens. Someone with years behind them has less room ahead, so their slow progress is often not a poor response but a normal place on the curve. How much room there is in total is covered in the piece on the upper limit of muscle growth.

Heredity is involved, but not as a single switch. There is no muscle gene. What is known points to a large number of small influences that add up: fibre size, recovery, how well someone tolerates volume, how easily training comes to them. That real differences exist is well supported. That they can be predicted from a genetic readout is not.

Part of the apparent difference is measurement error. Test the same person twice with no training in between and the numbers move. Scales, calipers and scanners all carry noise, and over short periods that noise is often larger than the real change. A number that shifts by two percentage points in a fortnight is telling you about water, not tissue.

What is likely but not settled

Sleep and stress probably explain more of the gap than people assume. The direction is clear: chronically short sleep degrades recovery and lowers session quality. How many kilos of muscle that costs over a year is not precisely known.

The best training dose probably is not the same for everyone. On average, more weekly sets produce more growth up to a point, but where that point sits for a given person is unresolved. Some do well on 10 sets per muscle group per week, some need closer to 20, and some fall apart at 20.

Effort varies more than the programme does. Two people running the same set close to failure are often nowhere near each other. Someone who habitually stops with six or seven reps in reserve is doing far easier work than someone stopping with one, and both will say they gave everything. How close to failure is actually useful is worked through in the piece on training with reps in reserve.

Fibre type composition probably matters. The reasoning is plausible and measurements exist, but the practical payoff is weak: without a biopsy there is no dependable way to know your own composition, so advice built on it is guesswork.

What gets repeated wrongly

“He's a non-responder.” The idea that someone does not respond to training at all tends to collapse as soon as the dose or the type of training changes. People who stall on one protocol usually move when sets go up, frequency changes or exercises are swapped. The accurate statement is that someone responded poorly to that specific programme.

Genetic testing for training. It is sold as a map and it is not one. Predicting training response from a saliva sample has so far shown no useful accuracy.

Body types. Sorting people into ectomorph, mesomorph and endomorph describes how someone currently looks rather than explaining why. As a predictive tool it has no value.

Comparisons with people who are not drug-free. A share of the speed difference visible online has nothing to do with heredity and everything to do with pharmacology, and it is rarely stated openly.

Genetics used as a diagnosis. The common error is reaching for the word before the basics have been checked, which turns it into a reason to change nothing. What is genuinely known about differing rates of progress is set out in the piece on individual response to training.

What this means for your training and eating

Before deciding you are slow, check that you are measuring something that actually moves. Weigh yourself three or four mornings a week and read the weekly average, not any single day. Keep a load log: going from 8 to 11 reps at the same weight is progress even when the scale sits still.

Give a programme 10 to 12 weeks before calling it a failure. Anything shorter cannot separate real progress from noise.

Fix the cheap things first. Protein at 1.6 to 2.2 g per kilogram of body weight per day, covered in more detail in the piece on daily protein intake. Sleep at 7 to 9 hours. If the goal is gaining, 200 to 400 kcal above maintenance, aiming for 0.25 to 0.5 per cent of body weight per week.

If all of that is in place and 12 weeks have produced nothing, change one variable rather than five. The usual candidates are raising weekly sets per muscle group by around 25 per cent, or taking sets one to two reps closer to failure so that the working sets carry real mechanical tension.

Then accept the part that does not move. Three years into serious training, adding two kilos of muscle in a year is not a failure; it is the expected rate.

When to see a doctor

Slow progress on its own is not a medical problem. But when it comes with constant fatigue, strength dropping for no reason, unplanned weight loss, loss of libido, heavy snoring with pauses in breathing, or periods stopping, that belongs in a consulting room rather than in a programme review. Anaemia, thyroid problems, sleep disorders and low sex hormones all produce a picture that looks exactly like a poor response to training. The same goes for pain lasting more than a few weeks or getting worse.

In short

• Differences in response to the same programme are real and wide, but almost everyone gains in something.
• The evidence is strongest that starting point, training age and actual effort explain a large share of the gap.
• Heredity cannot yet be usefully measured by a test and should not be the first explanation reached for.
• Before drawing conclusions: 12 weeks, tracked reps, 1.6 to 2.2 g/kg protein, 7 to 9 hours of sleep.
• If the stall comes with fatigue, unplanned weight loss or disturbed sleep, that calls for a check-up, not a new split.