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Breaking up time spent sedentary may help maintain muscle mass, according to new research. Lea Suzuki/The San Francisco Chronicle via Getty Images
  • Only about 23% of adults in the United States meet the recommended amount of weekly recommended cardio and strength training exercises.
  • Researchers from the University of Toronto have found short bursts of exercise, or activity “snacks” throughout the day can help a person better utilize the amino acids in the foods they consume.
  • Short exercise bursts during the day also help break up a sedentary lifestyle, resulting in less muscle loss.

Everyone knows exercise plays an important role in a person’s overall health. Current guidelines suggest adults perform 150 minutes of moderate-intensity workouts each week, including two days of strength training.

However, getting in enough physical activity every day can be hard due to heavy workloads and busy schedules. In fact, research shows only about 23% of U.S. adults meet national physical activity guidelines for both cardio and strength training exercises.

Previous research shows short bursts of exercise throughout the day benefit cardiovascular health, weight loss, and metabolic health.

Now, researchers from the University of Toronto add to this body of research with a new study that says periodic exercise “snacks” — such as two-minute intervals of walking or squats — can help a person break up periods of prolonged sitting and build muscle by using more amino acids from the foods they eat.

This study was recently published in the Journal of Applied Physiology.

Amino acids are known as the “building blocks” of protein. A person normally acquires the amino acids they need to build muscle through food sources — known as essential amino acids — or the body makes them itself — known as nonessential amino acids.

Foods high in essential amino acids include:

When a person consumes and digests a food protein source, the food’s amino acids are left behind. The body then uses those amino acids to make the proteins required to build muscle and perform other functions.

According to Dr. Daniel Moore, associate professor of muscle physiology at the Faculty of Kinesiology & Physical Education (KPE) at the University of Toronto and lead author of this study, researchers wanted to find out if breaking up sedentary time with brief periods of activity would help improve the way the body uses dietary amino acids for muscle protein synthesis — the body’s way of making new muscle protein.

“This type of lifestyle strategy has been shown to improve the removal of glucose (sugar) and fats from the blood, so we wanted to determine if it would do the same for amino acids,” he told Medical News Today.

Dr. Moore explained that proteins in our body, including muscle, are constantly being broken down into their constituent amino acids with new proteins built in their place. This “turnover” of protein ensures the removal of old or damaged proteins so new ones can be built to take their place.

“If we cannot build new ones as fast as old ones are broken down, then over time, we will lose muscle. However, any time we eat a protein-containing meal, our body (and especially muscles) use these amino acids to build new proteins, which ultimately is important to maintain overall muscle mass and quality.”
— Dr. Daniel Moore

For this study, researchers examined 12 participants — five women and seven men — for three trials lasting 7.5 hours each. During each trial, participants sat until they performed short bouts of walking or bodyweight squats every 30 minutes. The participants were also given two meals designed to mimic their breakfast and lunch.

Upon analysis, scientists found the short bursts of exercise helped the participants’ bodies better use the amino acids in the meals for muscle protein synthesis.

“[We] showed that the use of dietary amino acids to build new contractile myofibrillar proteins, which are responsible for generating muscle force, was increased. We believe that, over time, this would ultimately translate into the maintenance of muscle mass and function,” Dr. Moore explained.

He said this study shows that even reducing how long someone remains sedentary after a meal or throughout the day is important for setting the foundation for improving muscle health.

“Any non-disease condition in which our muscles are not used, such as prolonged bed rest, wearing a cast, or even just low daily step counts, is associated with a loss of muscle. This muscle loss is ultimately linked to a condition called anabolic resistance, which is a reduced ability to build new muscle proteins after a meal,” he said.

Medical News Today also spoke with Dr. Natasha Trentacosta, a pediatric and adult sports medicine specialist and orthopedic surgeon at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles, about this study. She said breaking up the monotony of sitting down all day can help improve and optimize a person’s ability to help build up skeletal mass from recent meals, particularly meals containing amino acids.

“Proteins are what makeup muscle mass, so if we’re better able to incorporate amino acids into our body, then we’re better at more efficiently building up skeletal muscle,” she added.

For those looking to incorporate more activity throughout their day, Dr. Trentacosta suggested finding ways to break up the monotony of sitting all day when at work.

“When you get to work or are leaving work, take the stairs instead of the (elevator). If you work in an office where you’re collaborating with other colleagues, instead of sending an email or making a phone call, walk into their office. And at lunchtime, instead of getting delivery, walking to the restaurant to pick up the food. (These are) quick, easy ways to add more activity to the day in short bursts.”
— Dr. Natasha Trentacosta