When we sit: textile electromyography identifies decreasing muscle activity and implications for metabolic health

Abstract Prolonged sitting is ubiquitous and increases risk of diabetes, heart disease and some cancers. A suspected mechanism behind the adverse cardiometabolic effects of prolonged sitting is low prevalence of muscle activity in these sitting bouts. Understanding muscle activity during sitting may provide insights for developing effective interventions. Using fabric-embedded wearable electrodes (electromyography; EMG), the activity of muscles can be directly investigated during many behaviours including sitting. We examined muscle activity during 7684 sitting bouts in daily living using EMG shorts in 84 adults from three separate cohorts (46% female; mean age (SD): 43.7 yr (18.7). When we sit, thigh muscle activity decreases, with muscle activity prevalence approaching its lowest levels after 25 minutes of sitting duration. Participants who usually sat for longer (≥25 minute durations) had the lowest sitting EMG levels compared with those with shorter bout durations. Sitting bouts that are preceded by more-intense and longer-duration physical activity show more sustained persistence of muscle activity during sitting. More frequent and intense interruptions to sitting result in 5 extra minutes of muscle activity prevalence per hour of sitting time. These findings provide new insights potentially underlying the metabolic health risks of prolonged sitting and suggest practical ways to counteract them.