Maintaining an adequate quantity and quality of skeletal muscle is important for health and functionality across the lifespan given its integral role in the regulation of postprandial glycemia and lipidemia, conversion of chemical energy to mechanical work, and contribution to whole body energy flux.
Prolonged periods of sitting are common in many workplace environments and higher-income countries, especially during shelter-in-place practices of pandemics. Periods of inactivity, such as immobilization, bedrest, or even more “benign” reductions in daily steps, result in a rapid deconditioning and loss of skeletal muscle that is associated with the development of “anabolic resistance”.
This “anabolic resistance” is characterized as a reduced ability to utilize dietary amino acids to synthesize new proteins, especially of the contractile myofibrillar fraction ). It has been argued that identifying means to prevent the development of anabolic resistance to enhance the remodeling of myofibrillar proteins would ostensibly be a means to replace fasted state losses and/or replace old/damaged proteins, which provide a theoretical basis for maintaining muscle mass and/or quality. Importantly, dietary amino acids represent the primary precursors of new muscle proteins, highlighting the importance of maintaining a robust ability to use exogenous amino acids to support tissue remodeling and protein synthesis. Thus, although direct links between myofibrillar protein synthesis and muscle health remain an active field of research, strategies aimed at maintaining a robust postprandial myofibrillar protein synthetic response have formed the scientific basis for recommendations aimed at optimizing muscle mass and function across the age and health span.
With prolonged periods of inactivity and/or sedentary time emerging as an independent risk factor for the development and/or progression of metabolic disease, interrupting sedentary time with brief periods of exercise has emerged as a practical tool to attenuate postprandial glucose and insulin excursions in otherwise healthy adults.
Interrupting prolonged sitting with periodic activity ‘snacks’ may help maintain muscle mass and quality
Daniel Moore, an associate professor of muscle physiology at the Faculty of Kinesiology & Physical Education (KPE) who led the study, found that short bouts of activity, such as two minutes of walking or body weight sit-to-stand squats, allow the body to use more amino acids from meals to build muscle proteins.
The researchers wanted to understand whether breaking up prolonged periods of sitting, a common occurrence in many workplace settings, would increase the ability of our muscles to use the building blocks of protein, called amino acids, from food to help them repair or replace old or damaged proteins.
They studied 12 people (seven men, five women) across three trials for seven and a half hours each. Participants were subjected to prolonged sitting interrupted every 30 minutes by short bouts of walking or body weight squatting. The activity helped improve the efficiency of dietary amino acids used for muscle protein synthesis, the process to repair or replace old or damaged proteins.
The 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.
Daniel R. Moore, Eric P. Williamson, Nathan Hodson, Stephanie Estafanos, Michael Mazzulla, Dinesh Kumbhare, Jenna B. Gillen (September 12, 2022). Walking or body weight squat “activity snacks” increase dietary amino acid utilization for myofibrillar protein synthesis during prolonged sitting. Journal of Applied Physiology. Retrieved from: https://journals.physiology.org/doi/full/10.1152/japplphysiol.00106.2022