Sitting Down is Acting Up

Written by Franchesca Buendia and Edited by Kevin Liu

On average, people sit for over 70 hours a week [1]. The time spent sitting down to eat, study, and watch television—amongst many other activities—easily accumulates into numerous sedentary hours that take a gradual toll on the body. A study has shown that it only takes two hours of sitting to feel discomfort in the lower back area in the form of stiffness and slight soreness. Additionally, cognitive function decreases when sitting down for a prolonged time; the same study shows that after two hours of sitting, the frequency of mistakes in problem-solving tasks increases [2]. Prolonged sitting also promotes “deconditioning” in muscles, which describes an individual’s decreasing tolerance of physical activity [3]. Muscles need to be exercised and regularly used in order to maintain their structural and functional integrity. When they do not engage in the activity needed to retain their strength, muscles become weaker and will require more energy when used. This explains the increased fatigue experienced when exercising muscles that have not been routinely used. Hence, inadequate exercise is associated with decreased strength, muscle mass, and flexibility [4]. 

Deconditioning can be prevalent throughout the body. The low stress levels typical of sedentary activities and decreased exercise results in a weaker heartbeat. This means that the heart is unable to pump blood efficiently enough to meet the oxygen demands of physical activity. The resulting oxygen shortage in the muscles make muscle fatigue more likely to occur. Additionally, reduced blood flow and a lack of movement in the lower body make blood clots more probable [3]. Blood clots pose a considerable risk to health, and may lead to venous thromboembolism (VTE), where a blood clot from one area of the body becomes dislodged and travels to another area. The dislodged blood clot can potentially obstruct blood vessels of the lungs, brain, or other organs where blood flow is crucial for functioning— in extreme cases, VTE blockages can starve cells of oxygen and nutrients [5]. 

However, the negative effects of long-term sitting may be balanced by thirty minutes of daily exercise [1]. As different exercises’ effectiveness varies from person to person, physical activity should engage the muscles that are not normally contracted throughout the day, as those are the ones most susceptible to deconditioning (such as the legs, arms, and abdominals). Thus, individual bodily needs are best met through personally tailored and consistent exercise. Regular exercise promotes muscle repair and oxygenation, lowering the risk for blood clots and decreasing fatigue levels [3].

References:

1. Hamilton, M. (2018). The role of skeletal muscle contractile duration throughout the whole day: reducing sedentary time and promoting universal physical activity in all people. Journal of Physiology, 596:1331–1340. 
2. Baker, R., Coenen, P., Howie, E., Williamson, A., Straker, L. (2018). The Short Term Musculoskeletal and Cognitive Effects of Prolonged Sitting During Office Computer Work. International Journal of Environmental Research and Public Health, 15:1678. 
3. Lurati, A. (2018). Health Issues and Injury Risks Associated With Prolonged Sitting and Sedentary Lifestyles. Workplace Health & Safety, 66:285–290. 
4. Harding, Mary. “Muscle Weakness.” Patient, 2016, https://patient.info/signs-symptoms/tiredness-fatigue/muscle-weakness, Accessed 18 April 2020.
5. Beckman, M., Hooper, W., Critchley, S., Ortel, T. (2010). Venous Thromboembolism: A Public Health Concern. American Journal of Preventive Medicine, 38:495–501.