For individuals who spend long hours working in front of a computer, studying, or driving, remaining seated for large parts of the day may seem inevitable. However, prolonged lack of movement impacts not only energy consumption but also muscle activity, leg circulation, and how the body processes glucose.
This pattern is called sedentary behavior. The World Health Organization (WHO) defines this term as any activity performed while awake in which a person remains seated, reclined, or lying down, expending up to 1.5 METs of energy. It is important to note that sedentary behavior and physical inactivity are not equivalent; a person can exercise regularly and still spend many hours sitting during the rest of the day.
In Brazil, a 2019 survey, the National Health Survey, indicated that 30.1% of adults reported having six or more hours of sedentary behavior daily. This data was collected through self-reporting and therefore does not represent a direct measurement of the exact time each participant spent sitting.
One effect can be noticed in the legs. Normally, when walking, the contraction of calf and thigh muscles aids in returning blood to the heart. However, during long periods of sitting, these muscles exhibit a lower level of activity.
André Pêgas, a physiotherapist, osteopath, and CEO of the Doctor Hernia clinic, explains that although the heart is the main organ for pumping blood, there are other muscles that assist in venous return. He details that the thigh and calf musculature helps return blood from the lower limbs to the heart, and the lack of contraction in these muscles can compromise this return.
In this scenario, some people may experience swelling in their legs or ankles after long periods of sitting. Furthermore, experimental studies suggest that sitting for several hours can cause temporary changes in the vascular function of the legs. A meta-analysis identified a decrease in flow-mediated dilation in the lower limbs after 120 and 180 minutes of continuous sedentary behavior.
Lack of movement also affects the activity of large muscle groups. Anderson Clayton Sant’Anna, a sports physician and nutrologist, member of the INKI medical platform and physician at Paraná Clube, states that when one spends many hours sitting, especially without moving the legs, the body's muscles enter a state of low activity. This results in reduced energy expenditure and decreased glucose utilization by the muscles, an effect particularly relevant after meals.
Skeletal muscles play a crucial role in removing glucose from the bloodstream because muscle contraction intensifies glucose uptake into cells, while prolonged inactivity reduces this stimulus. Sant’Anna clarifies that the muscle is one of the main entities responsible for removing glucose from the blood, and this action is reduced when a person remains almost motionless for hours. After eating, the body may require a greater insulin response to manage glucose.
The doctor emphasizes, however, that spending a few hours sitting does not necessarily imply the development of diabetes. The problem lies primarily in repeated and prolonged exposure to sedentary behavior, especially when there is little physical activity for the rest of the day.
Scientific literature allows distinguishing rapid changes from effects that may be linked to long-term health. A systematic review and meta-analysis published in 2026 analyzed 53 studies, with 39 included in the quantitative analysis. Compared to continuously sitting, interrupting this period with small activities demonstrated a reduction in glucose and insulin response after meals. Among the protocols examined, breaks involving walking showed the most expressive results.
However, this does not prove that such breaks, in isolation, prevent diabetes or other diseases in the long term. Most of these studies focused on acute responses, specifically changes in glucose and insulin after meals.
When the analysis extends from changes observed in a few hours to outcomes that emerge over years, the nature of the evidence changes. Observational studies establish correlations between higher levels of sedentary behavior and an increased risk of cardiovascular problems, type 2 diabetes, and mortality. For this reason, the WHO advises limiting sedentary time and replacing it with physical activity of any intensity.
Firmino Haag, a cardiologist and coordinator of Cardiology at Albert Sabin Hospital (HAS), states that it is difficult to attribute the cause of the disease solely to the act of sitting. For him, sedentary behavior creates physiological conditions that can contribute to the development of cardiovascular diseases over time.
Haag also points out that scientific evidence shows a constant link between long periods of sitting and a higher risk of cardiovascular diseases, type 2 diabetes, and all-cause mortality. He warns, however, that science is still trying to precisely define how sitting time relates to these risks, highlighting the difficulty of separating this behavior from other factors, such as diet and genetics.
Therefore, it is inappropriate to turn epidemiological findings into a rigid rule, such as 'after a certain number of hours sitting, the person starts running a risk.' The WHO recommends restricting sedentary behavior but does not establish a universal daily limit of safe sitting hours for all adults.
It is possible to reconcile regular exercise practice with long periods of sitting. Haag warns those who exercise but spend most of the day sitting. For him, exercise is essential, but it should not be seen as a complete compensation for extreme periods of sedentary behavior.
The WHO itself addresses these two dimensions complementarily. For adults, the guideline is a minimum of 150 to 300 minutes per week of moderate aerobic activity, or 75 to 150 minutes of vigorous activity, complemented by muscle strengthening exercises at least two days a week. The organization also advises limiting sedentary time and replacing it with physical activity.
Studies indicate that breaking up long periods of sedentary behavior can improve certain physiological responses, mainly in glucose metabolism. The 2026 meta-analysis found that interrupting long periods of sitting through small activities reduced the postprandial glucose and insulin response, with breaks involving walking having the greatest effects.
Sant’Anna summarizes this finding by saying that 'getting up, walking for a few minutes, climbing stairs, or performing some light activity can already help.' For him, the studies suggest that walking may be more beneficial than just standing to optimize metabolic response.
A systematic review specifically compared standing versus light walking during prolonged sitting periods. The results showed a reduction in postprandial glucose in both tactics, but walking had a greater impact and also reduced the insulin response.
This does not mean that standing is useless. The result indicates that, in the tested protocols, walking generated more consistent metabolic effects than remaining still.
There is still no universal interval defined as a rule for everyone. In the 2026 review, protocols that interrupted sedentary behavior every 15 to 20 minutes showed the largest drops in glucose and insulin among the frequencies evaluated. This suggests that this interval arose in protocols with the best results, not that science established it as a mandatory recommendation.
Sant’Anna argues that the data point to benefits with frequent interruptions, but warns: 'There is still no universal 'magic number'.' He mentions 30 minutes as a practical reference to avoid long continuous sitting periods, noting that some studies found superior results with 15 to 20-minute intervals.
André Pêgas, for his part, suggests interrupting the sitting period every 40 to 50 minutes for about five minutes, performing movements to activate the leg muscles.
The different recommendations require caution, as there is no single break protocol applicable to everyone. The common point among the evidence is to avoid long periods of continuous immobility and integrate more movement throughout the day.
The musculoskeletal system can also be affected by staying in the same position for too long, but the relationship between sedentary behavior and lower back pain is more complex than simply stating that 'sitting causes back pain.' Pêgas emphasizes factors such as inadequate chair support, lack of posture change, and reduced muscle mobility. He states that 'the sitting position favors the shortening of leg muscles.' Prolonged immobility and postural changes can lead to mechanical overload in the lumbar region.
However, literature reviews have presented varied results regarding the connection between sitting time and lower back pain, which prevents a simple conclusion of cause and effect. A systematic review on sedentary behavior and musculoskeletal pain found associations in certain scenarios but highlighted limitations in determining causality.
In practice, the focus should not be on finding an ideal posture for hours, but rather on alternating positions and interrupting long periods of immobility. It is not necessary to turn every break into a workout. The goal is to reduce the time of continuous immobility and include small opportunities for movement throughout the day.
This can involve getting up to get water, walking to another location, using stairs on certain occasions, or simply changing position and moving the legs. Sant’Anna points out that these breaks can be simple and do not need to replace a workout session. Pêgas also recommends adding movements to breaks, such as walking and activating the leg muscles, but reminds that these interruptions do not replace regular physical activity. For him, breaks during work are preventive measures, while exercise, strengthening, and other activities must remain in the routine.
Therefore, the suggestion is not to exchange exercise for breaks or spend the day standing, but rather to combine regular physical activity with fewer prolonged periods of immobility.
