Exercise can make us fitter and reduce our risk for diseases such as diabetes and heart disease. But how actually this works has remained a mystery. New research claims that the answer may lie, in part, in our DNA. Exercise changes the shape and functioning of our genes.

The human genome is highly complex and dynamic, with genes constantly turning on or off, depending on what biochemical signals they receive from the body. When genes are turned on, they express proteins that prompt physiological responses elsewhere in the body. But we don’t know how these genes respond to exercise.

Epigenetics is a process by which the operation of genes is changed, but not the DNA itself. Epigenetic changes occur on the outside of the gene, mainly through a process called methylation. In methylation, clusters of atoms, called methyl groups, attach to the outside of a gene like microscopic mollusks and make the gene more or less able to receive and respond to biochemical signals from the body.Scientists know that methylation patterns change in response to lifestyle. Eating certain diets or being exposed to pollutants, for instance, can change methylation patterns on some of the genes in our DNA and affect what proteins those genes express. Depending on which genes are involved, it may also affect our health and risk for disease.

For a study published this month in the journal EPIGENETICS, the scientists at the Karolinska Institute in Stockholm made 23 volunteers to bicycle using only one leg, leaving the other unexercised. In effect, each person became his or her own control group. Both legs would undergo methylation patterns influenced by his or her entire life; but only the pedaling leg would show changes related to exercise. The volunteers pedaled one-legged at a moderate pace for 45 minutes, four times per week for three months. Then the scientists repeated the tests with each volunteer.

Using genomic analysis, the researchers determined that more than 5,000 sites on the genome of muscle cells from the exercised leg now featured new methylation patterns. Some showed more methyl groups; some fewer. But the changes were significant and not found in the unexercised leg. Interestingly, many of the methylation changes were on portions of the genome known as enhancers that can amplify the expression of proteins by genes. And gene expression was noticeably increased or changed in thousands of the muscle-cell genes that the researchers studied. Most of the genes in question are known to play a role in energy metabolism, insulin response and inflammation within muscles.

But it’s unknown whether the genetic changes scientists observed would remain if someone quits exercising and how different amounts or different types of exercise might affect methylation patterns and gene expression.The message is that we can induce changes that affect how we use our genes and, through that, get healthier and more functional muscles that ultimately improve our quality of life.



Lindholm ME, Marabita F, Gomez-Cabrero D, Rundqvist H, Ekström TJ, Tegnér J, Sundberg CJ.An integrative analysis reveals coordinated reprogramming of the epigenome and the transcriptome in human skeletal muscle after training.Epigenetics. 2014 Dec 7.