Identical twin study sheds light on how exercise tunes our genes:

One fascinating study back in 2014 homed in on the way exercise affects gene expression by tasking a small cohort of volunteers to perform a one-legged cycling task for three months. At the end of the study period the researchers saw changes in about 4,000 genes when studying skeletal muscle from the exercised leg compared to the untrained leg.

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The researchers recruited 70 pairs of identical twins. Alongside measuring their body-mass index and surveying their exercise habits, each participant wore a fitness tracker for one week to objectively ascertain their physical activity levels.

A twin pair was determined to be “discordant” if one twin completed more than 150 minutes of vigorous physical activity a week while the other twin performed less than 150 minutes in a week. Around 40 percent of the twin pairs were found discordant on this measure.

Looking at the epigenetic variances between these physically discordant identical twin pairs, the researchers found markers on over 50 genes. The exercise-induced gene expression changes were found in genes previously associated with a lower risk of metabolic syndrome

In other words, exercising doesn’t just give you stronger muscles, it also changes a whole bunch of gene expressions. It would be interesting to find out how that impacts the next generation. Does the child of the twin who decided to exercise more start out with a different set of gene expressions than the child of the twin who chose not to exercise?