This article on genetic determination of exercise requirements is slightly more research based and technical than normal, so you might require your researcher hat.
The Family Heritage Study
The Heritage Family Study is a huge project that has been going since 1992. Its stated main goals are ‘to examine the role of the genotype in the cardiovascular and metabolic responses to aerobic exercise training, as well as those changes brought about by regular exercise for several cardiovascular disease and diabetes risk factors.’ So basically, if this article was a space ship then their domain area is pretty much galactic in size! And if so, then we are going to examine one small cluster of planets floating around small star somewhere in the many galaxies that make up the universe.
Let’s leave the spacey for the scientific! Time for our researcher hats…
VO2 max is one of the specific phenotypes examined by the Family Heritage Study. They examined how exercise impacts on VO2 max in a large population sample. VO2 max can be briefly defined as the maximum volume of oxygen (maximal oxygen uptake) that can be utilized in one minute during maximum or exhaustive exercise.
Large Variation In Sedentary VO2 Max
The first part of the study examined whether families had a similar VO2 max at the start of the training. It was shown that genetic factors accounted for about 40% of variance in initial VO2 max, after adjusting for age, sex, body mass and body composition.
Large Variation In VO2 Max Improvement With Exercise
The second part of the study examined changes in VO2 max at the end of a 4 hour per week, 20 week exercise program. The average VO2 max increase was found to be 19%.
However, what was interesting was the huge variation in VO2 max increases that occurred. 5% of subjects had little or no change in VO2 max (<5%). The most improved 5% had a change in VO2 max of anywhere from 40% to above 50%!
These massive variations occurred for all age categories, races, initial fitness levels or gender. There was two and a half times more variation between families as opposed to within families for change in VO2 max, with a maximum heritability of around 47%.
Initial VO2 Max And VO2 Max Change After Training Linked To Different Genes
Rather interestingly, there was no correlation between initial VO2 max and the change in VO2 max due to the exercise regime. They therefore concluded that one set of genes influenced initial VO2 max levels, and a different set influenced the change in VO2 max possible based on the exercise program.
Despite the wealth of different variables that the study has data for, they could not find any non-genetic factors that explained the variance between exercise responders and exercise non responders.
They discovered that DNA sequence variant in the muscle form of the creatine kinase gene (CKM) appeared to be partly responsible for the change in VO2 max after training. They give the example that ‘about 30% of the low responders were homozygotes (i.e. an organism with identical pairs of genes for a specific trait) for this variant while there were no homozygotes among the high responder.’
Both sedentary VO2 max (i.e. without regular exercise) and the degree of improvement of VO2 max with exercise vary quite widely between different people. There is clearly a hereditary link to this. Interestingly different genes appear to be responsible for these two VO2 max variables. This does not necessarily mean that non-responders are not benefitting from the exercise! What this means though is that VO2 max exercise non responders might require different amounts of exercise or indeed different types of exercise to maximise increases in VO2 max.
The Family Heritage Study, http://www.pbrc.edu/heritage/publications.html