It is time to have a rest: How do break types affect muscular activity and perceived discomfort during prolonged sitting work

Abstract BACKGROUND Prolonged sitting at work can lead to adverse health outcomes. The health risk of office workers is an increasing concern for society and industry with prolonged sitting work becomes more prevalent. OBJECTIVE This study aimed to explore the variation in muscle activities during prolonged sitting work and found out when and how to take a break to mitigate the risk of muscle symptoms. METHODS A preliminary survey was conducted to find out the prevalence of muscle discomfort in sedentary work. Firstly, a 2-hrs sedentary computer work was designed based on the preliminary study to investigate the variation in muscle activities. 24 participants took part in the EMG (electromyography) measurement study. The EMG variations in the trapezius muscle and latissimus dorsi were investigated. Then the intervention time was determined based on the EMG measurement study. Secondly, 48 participants were divided into six groups to compare the effectiveness of every break type (passive break, active break of changing their posture, and stand and stretch their body with 5 or 10 mins). Finally, data consisting of EMG amplitudes and spectra and subjective assessment of discomfort were analyzed. RESULTS In the EMG experiment, results from the JASA (joint analysis of the spectra and amplitudes) method showed muscle fatigue after about 40 mins of sedentary work. In the intervention experiment, the results showed that standing and stretching for 5 mins was the most effective break type, and this type of break could keep the muscles’ state at a recovery level for about 30−45 mins. CONCLUSIONS This study offers the possibility of being applied to office workers and provides preliminary data support and theoretical exploration for a follow-up early muscle fatigue detection system.