Activity "snacks” to break up sitting may help regenerate muscle

The body of evidence around the negative health impacts of sitting down all day continues to build, and with this comes new ideas around how folks can manage the risks. A new study has delved into the metabolic effects of getting up for a short spurt of exercise, such as a two-minute walk, and shown it can improve sugar processing after a meal and help maintain muscle mass and quality.

Led by researchers at the Canada University of Toronto, the study focused on one of the many health impacts of sedentary lifestyles, which is the loss of muscle mass and quality. This centers on the function of myofibrillar proteins, which the body fashions out of amino acids and are key components of skeletal muscle, making up almost three-quarters of all the muscle proteins in the human body.

Previous research by the group had shown that extended periods of sitting can hamper the body’s ability to filter sugars from the blood after a meal and that interspersing bouts of exercise into prolonged periods of sitting can help regulate blood sugar. The researchers have now set out to investigate what effects sitting might have on the ability of the body to use dietary amino acids for the synthesis of myofibrillar proteins, and ultimately maintain its muscle mass.

“This is critical to ensure the body has an adequate quantity and quality of muscle,” said Daniel Moore, lead author of the study.

The study enlisted 12 people who were made to sit for prolonged periods of more than seven hours, with some of the subjects interrupted every 30 minutes for a short bout of walking or body weight squatting. The scientists found those regularly hopping up for stints of physical activity had an enhanced ability to use amino acids from the food for synthesis of myofibrillar proteins.

The scientists describe these brief spurts of exercise as activity “snacks” and write that the difference they had in promoting the use of dietary amino acids for protein synthesis was “moderate-to-large.”

“This is significant because prolonged periods of low muscle activity – from sitting, wearing a cast, or bed rest – is associated with a loss of muscle mass that occurs in parallel with or because of an inability of our muscle to build new proteins after we eat a protein-containing meal,” said Moore. “Our results highlight the importance of breaking up prolonged sedentary periods with brief activity snacks. We believe they also highlight that moving after we eat can make our nutrition better and could allow more dietary amino acids from smaller meals or lower quality types of protein to be used more efficiently.”

The research was published in the Journal of Applied Physiology.