It can be hard to find motivation to exercise, but new research suggests it could be as simple as flicking a switch in the brain.
Scientists in Texas have accidentally found a way to get mice off their little mice couches and into the running wheel, and think it might work in humans too.
They were testing whether a gene called Dnmt3a was linked to weight. By turning it off, they expected the mice to gain weight.
"Somewhat disappointingly, however, the Dnmt3a-deficient mice were only slightly fatter than those that were not deficient," said study author Harry MacKay.
Investigating further, they found the mice with the gene turned off ate no more or less than those with it turned on. So how did they end up slightly fatter?
It turns out mice with the Dnmt3a gene turned off spent only half as much time on the running wheels as the mice with it turned on.
They were just as capable of going for a jog, the scientists said - but, as many of us would appreciate, they really didn't want to. Turning the gene on or off - a process known as epigenetics - affected how willing the mice were to exercise.
"Our findings suggest that epigenetic mechanisms, such as DNA methylation, that are established in the brain during fetal or early postnatal life, play a major role in determining individual propensity for exercise," said co-author Robert Waterland.
"Nowadays, as decreases in physical activity contribute to the worldwide obesity epidemic, it is increasingly important to understand how all of this works."
And whether it works in humans too.
The findings were published in journal Nature Communications.