The Principle of Individuality: Why the Same Program Gives Different Results
Quick Intro
The principle of individuality states that people respond differently to the same training. Two people who follow an identical program can gain very different amounts of strength, size or fitness. Training works best when it is adjusted to the person’s goals, abilities, health, preferences and circumstances.
The Idea in Plain Terms
Individual differences come from many sources:
- Genetics. Inherited traits affect how much fitness or muscle a person gains from training.
- Training history. A beginner improves faster than someone who has trained for years.
- Age and sex. Recovery speed and hormone levels differ.
- Sleep, nutrition and stress. These shape how well the body adapts.
- Lifestyle. Work, family and time shape what plan is sustainable.
- Preferences. People stick with activities they enjoy.
The principle has two practical consequences. First, a published program is a starting template and needs adjustment. Second, comparing your progress with someone else’s is of limited use.
A Worked Example
Two friends begin the same three-day lifting program:
| Person | Starting point | After 12 weeks |
|---|---|---|
| A | Slept well, ate plenty of protein, quick to adapt | Large gains in strength |
| B | Slept five hours, high stress, ate little | Small gains in strength |
Person B changes sleep and food first, instead of changing the program. Person A may need a harder plan sooner. Both adjustments are acts of individualization.
What the Research Shows
The most cited studies measure how widely people vary. In the HERITAGE Family Study, 481 sedentary people did the same 20-week endurance program, and the change in aerobic capacity ranged from almost no improvement to large increases, with genetics accounting for a substantial share of the difference. A study by Hubal and colleagues in 2005 had 585 adults do a 12-week arm strength program, and muscle size changes ranged from a small loss to a very large gain, though most people gained some.
The term “non-responder” is used for people who show little change on a measure. Statisticians have pointed out that part of what looks like non-response is measurement error and day-to-day variation, so apparent differences are overstated. Studies also show that many people who do not respond on one outcome do on another, or respond when the program changes, such as increasing the dose.
The general conclusion is that variation is real and large, and almost everyone improves with enough well-designed training.
Who It Suits
This principle applies to everyone, and it especially matters to:
- Coaches working with groups.
- People who feel discouraged comparing themselves to others.
- Those who stall on a standard program.
How to Use It
- Treat any program as a starting point.
- Track your own results over 8 to 12 weeks.
- Change one variable if progress stalls, such as volume or sleep.
- Choose activities you can keep doing.
- Compare yourself to your past self.
- Seek advice if you have health conditions.
Common Misunderstandings
It is not an excuse to ignore training basics.
It is not true that some people cannot improve.
It is not a reason to change plans every week.
FAQ
Are some people non-responders? Few people fail to respond to every kind of training.
How much does genetics matter? It matters a lot for how much, and training helps everyone.
Should I copy a champion’s program? It may not suit your body or schedule.
How do I find what works for me? Test changes one at a time and track results.
Where This Comes From
Bouchard C and colleagues, 1999, familial aggregation of VO2max response to exercise training: results from the HERITAGE Family Study (Journal of Applied Physiology, 87, 1003 to 1008). Hubal MJ and colleagues, 2005, variability in muscle size and strength gain after unilateral resistance training (Medicine and Science in Sports and Exercise, 37, 964 to 972). Commentary on measurement error appears in work on individual response by Hopkins, Atkinson and others.
Related to: FITT, specificity, variation and menstrual cycle periodization.