Back pain is an important concern in terms of public health.1 In addition to its high prevalence, back pain is associated with physical constraints, lower quality of life, and reduced life expectancy.2,3 Although back pain is a major public health problem worldwide, it is projected that the burden of back pain will increase even further in the next few decades, especially in low and middle-income countries.2

One of the main challenges when considering back pain at the population level is that the cause is frequently non-specific, being associated with socioeconomic, physical, behavioral, and mental factors.2,4 Among the causes, in general, healthy lifestyles are suggested as protective against back pain; however, doubts remain about the doses and combinations of healthy behaviors to optimize benefits. Although moderate-intensity physical activity in leisure time seems protective for back pain symptoms,5,6 this is not clear considering other domains of physical activity and specific population groups.7 In addition, little is known about the combination of physical activity with other movement behaviors, such as sedentary time spent on TV-viewing and on personal computers.7

Given the social restriction measures imposed due to the Coronavirus Disease 2019 (COVID-19) pandemic, people's lives have changed and “stay-at-home” messages have reduced opportunities for physical activity practice and increased exposure to many types of sedentary behaviors. Therefore, increases in the level of physical inactivity and sedentary behavior have been reported during the COVID-19 quarantine.8 These behavior changes seem to be associated with cardiovascular,9 metabolic,10 and mental health disorders.11 However, it is not clear how changes in movement behaviors due to the COVID-19 pandemic are associated with musculoskeletal conditions, such as back pain. This information would help the development of interventions to mitigate the potentially harmful effects of quarantine on musculoskeletal health, focusing on the specific type and pattern of movement behaviors. Thus, we investigated the association of changes in movement behaviors due to the COVID-19 pandemic quarantine with back pain among Brazilian adults. Our hypothesis was that increased physical inactivity and high screen-based sedentary time due to the COVID-19 pandemic quarantine are associated with the incidence and worsening of back pain.

We investigated associations between patterns of movement behaviors and back pain during the first phase of the COVID-19 pandemic quarantine among Brazilian adults. Our main findings were that physical inactivity and elevated sedentary behaviors due to the COVID-19 pandemic quarantine increased the likelihood of the incidence and worsening symptoms of back pain among those who already had back pain before the pandemic. In this sense, consistently inactive people and those who maintained high computer/tablet use were more affected during the quarantine. Among people who reported high TV-viewing, participants who changed to presenting high TV-viewing were the most affected.

Limitations of the current study include the use of online questionnaires for data assessment, which can imply memory bias (in the case of retrospective information). However, in quarantine times, interviews, or even the use of device-based methods to assess movement behaviors are not possible. The online administration of the questionnaires can also limit access to less affluent people, especially in a middle-income country context. The interpretations of the current findings should consider the opinion of the participants about their back pain being caused by changes in their habitual activities, because questions about changes in back pain during the pandemic included: "back or spinal pain due to the changes in habitual activities". In addition, more details about household activities during quarantine (e.g. carrying weight, squatting, or kneeling) would help in understanding the complex relationship between movement behaviors and back pain in these times. Finally, this is a cross-sectional survey, with limitations in attributing causality. However, this study includes more than 43,000 people from one of the countries most affected by the COVID-19 pandemic, which provides valuable insights into how movement behaviors are associated and can be used to prevent back pain during these difficult times. To the best of our knowledge, this is the first national survey linking changes in movement behaviors due to the COVID-19 pandemic quarantine and back pain.

Other studies from the National Health Survey point out the magnitude of low back pain in the Brazilian population (∼18%).12,18 Although there is no consensus about the overall effect of physical activity on back pain,19 consistent evidence suggests that, especially, leisure-time physical activity at moderate intensities reduces the risk of back pain.6,20 In Brazil, physical exercise/physical therapy was the second most commonly used intervention to treat back pain.4

During the quarantine periods, people are encouraged to stay at home, limiting opportunities to be active (≥150 min/week of moderate physical activity). In this sense, our findings indicate that consistently inactive people and especially those who have become inactive during the quarantine are more likely to report back pain incidence and increased symptoms, which corroborates previous findings.21 This result can be at least partially explained by reduced muscle strength, muscle mass, and flexibility associated with physical inactivity,22 which in turn increase the risk of back pain.23 Interestingly, this relatively short period of inactivity (∼1–2 months) is enough to increase the likelihood of worsening back pain, corroborating previous findings on the harmful effects of short periods of inactivity in other biological systems.24,25 Thus, actions to encourage people to be active during quarantine periods should be developed to mitigate the burden of back pain and the consequences. Although some initiatives have been launched during the COVID-19 pandemic to support an active lifestyle,26 such as physical exercises at home, further studies are needed to identify the effectiveness of these actions.27

In addition to the reduced opportunities for physical activity, people are more prone to sedentary behaviors during quarantine periods. Although the association between sedentary behaviors and back pain is less clear and tends to vary according to occupational status,19,28,29 prolonged sitting seems to be detrimental to musculoskeletal symptoms.30 Here, we observed that becoming more sedentary during the COVID-19 pandemic quarantine increases the likelihood of the incidence of back pain, but only increased TV-viewing was associated with worsened back pain. On the other hand, consistent computer/tablet users were more prone to both an incidence of and increased back pain symptoms, which did not occur among the consistently high TV-viewing group. These results reinforce previous evidence showing that not all sedentary behaviors are equal.31,32 In this case, both TV-viewing and computer/tablet use are behaviors generally performed in different environments and for different purposes. This could suggest that the routine of those who already presented high TV-viewing before the pandemic was less affected in comparison with those with consistent computer-tablet use, especially considering adaptations needed to use a computer/tablet during the quarantine, such as the ergonomic environment.

An unexpected result was the increased likelihood of worsening back pain (not incidence) among those who changed to spending <4 h/d in computer/tablet use during the pandemic. We suppose that this represents specific population sub-groups that were overloaded with family activities, which can be associated with prolonged standing time, inadequate posture, and musculoskeletal disorders.19 In addition, reduced computer/tablet use could also be replaced by other types of sedentary behavior, such as more TV-viewing, explaining the higher likelihood of worsened back pain. Given our cross-sectional design, the non-use of the computer and tablet may also have occurred due to the worsening back pain, resulting in the inability to use computers for a long time. This result highlights how the complex composition of daily activities can explain musculoskeletal health. Future studies should consider a wider range of movement behavior information (e.g. type, intensity, duration) with objective measures of the patterns of physical activity and sedentary behaviors (e.g. bouts and breaks).

These findings highlight how patterns and changes in specific movement behaviors due to the COVID-19 quarantine affected musculoskeletal health. Although the reports could represent isolated episodes of back pain, persistent cases could disable people, affecting quality of life and the health systems.2 These results should support policies from Primary Health Care managers, supporting physical activity programs, such as the Health Academy Program,33 as well as supporting the maintenance of family health support teams (NASF), which need to be financed, and expansion of the supply of professionals, such as physical therapists, physical educators, and others, who can act in primary care, minimizing the effects of musculoskeletal diseases, such as back pain, in the post-pandemic period.

Physical inactivity and elevated sedentary behaviors due to the COVID-19 pandemic quarantine are associated with the incidence and worsening symptoms of back pain among Brazilian adults. These findings reinforce the need to promote active lifestyles during periods of quarantine to mitigate the burden of pandemics on people's health.