Is Occupational Physical Activity Harmful to Health?

A recent webinar from the National Occupational Research Agenda’s Cancer, Reproductive, Cardiovascular, and Other Chronic Disease Prevention (CRC) cross-sector council describes research related to the potential effects of occupational physical activity on workers’ cardiovascular health. This blog summarizes the webinar and discusses the differences between (1) leisure-time physical activity, and (2) occupational physical activity in relation to cardiovascular health and other potential health concerns. The blog also highlights the need to consider the type of physical activity in current and future research so the health of all people is addressed. This includes those with cardiovascular disease and individuals employed in sedentary and physically active jobs, as well as during pregnancy.

What are the domains of physical activity?

Being physically active is known to improve health. Physical Activity Guidelines for Americans, second edition was created by the U.S. Department of Health and Human Services to outline the most recent understanding of the health benefits of physical activity. These guidelines recommend that adults should perform at least 150 minutes of moderate intensity physical activity per week for substantial health benefits. The current guidelines consider all physical activity, no matter the setting, as contributing towards this goal. There is emerging evidence related to the health benefits and risks of physical activity at work that could be considered in the development of the next guidelines.

New research suggests that the setting in which physical activity occurs may matter for health. These are the four physical activity domains¹:

1. Leisure-time physical activity (we refer to this simply as “leisure activity” for the purpose of this blog) is done at one’s discretion when one is not working, transporting to a different location, and not doing household chores. Exercise, going for a walk, and playing games or sports (e.g., badminton, pickle ball, basketball) are all examples of leisure-time physical activity.
2. Household physical activity is done in or around one’s home and involves performing household tasks such as cooking, cleaning, home repair, yardwork, or gardening.
3. Transportation physical activity is done in order to get from one place to another. Examples include walking to a convenience store or bicycling to a park.
4. Occupational physical activity (we refer to as “physical activity on the job” for the purpose of this blog) is performed while one is working. Examples include stocking shelves in a store, swinging a hammer, or delivering packages in an office.

^{Photos © Getty Images}

What is the physical activity health paradox hypothesis?

The Physical Activity Guidelines for Americans, second edition was released in 2018 providing the most current science on the health benefits of physical activity. Since the Guidelines were published, emerging evidence has suggested that the health impacts of physical activity on the job may differ from the health effects of other types of physical activity. While most leisure activity is known to improve health in the general population, recent evidence suggests physical activity on the job may adversely impact health, particularly cardiovascular health. These different impacts of physical activity on the job versus physical activity in other settings are known as the physical activity health paradox hypothesis.^2,3

What potential health risks are associated with physical activity on the job?

• 

  Men with high physical activity on the job were found to have an 18% higher risk of early death compared with those engaging in low level physical activity on the job. This is based on a meta-analysis of 17 different studies on physical activity on the job and all-cause mortality.⁴

• High physical activity on the job increased overall cardiovascular disease (CVD) risk by 24%, while leisure activity decreased overall CVD risk by 34%.⁵ This is based on a meta-analysis of 23 studies on physical activity on the job and cardiovascular disease.
• Jobs that mostly require standing were associated with a double (2-fold) risk of incident heart disease compared to jobs that mostly involve sitting.⁶ This is based on a 12-year cohort study of Canadian workers examining working postures, such as occupational standing, and heart disease using administrative information about job exposures (data was not self-reported).

These and other emerging research findings suggest high physical activity on the job and prolonged standing at work may increase CVD and risk of death. The potential differences in exposure to physical activity on the job and health risks between men and women are unclear and need to be further examined.

Researchers may want to consider:

1. Distinguishing physical activity on the job from physical activity done during leisure-time.
2. Not combining sitting and standing in a “low” or “sedentary” reference group. When possible, standing should be analyzed on its own and not combined with other work-related demands.
3. Differentiating between the health effects resulting from routine, high levels of physical activity on the job from the health effects resulting from jobs with episodic periods of high-intensity physical activity, such as that occurring among firefighters.

Why some physical activity on the job might be harmful to health?

Researchers don’t fully understand why some physical activity on the job is linked to increased risk for cardiovascular disease and death. ^7-10

However, several potential explanations of the physical activity health paradox have been proposed.³

1. Increased risk factors for heart disease

Some data suggests that the physical activity performed by some occupational groups such as food service or retail workers may be too low in intensity or too long in duration for maintaining or improving cardiovascular fitness and health.^11,12 For example, physical activity on the job could lead to sustained elevations in heart rate and blood pressure or cardiovascular strain throughout the day, which negatively impacts health.^13,14

Some other studies suggest that high intensity or high amounts of physical activity on the job over time without adequate recovery may trigger increased inflammation within the body, which may be harmful.

2. Jobs with little control and high demand can be stressful

A worker’s perceived lack of control/decision-making over physical tasks combined with a high task demand or inadequate reward including salary, esteem, security, and promotion prospects in the workplace may contribute to heightened job stress. This may negatively impact overall health and exaggerate the negative cardiovascular strain of physical activity on the job.

While some evidence supports these proposed explanations, they are still being studied and require further research for validation. Occupational safety and health researchers could learn from additional studies in related fields, such as athletics, cardiovascular health, and job stress.

As more is learned in this area, evidence-based strategies can be developed to prevent or lessen the potential adverse effects of physical activity in the workplace.

Employers may be able to prioritize the well-being and cardiovascular health of workers in physically demanding jobs by promoting a balanced and well-managed approach to physical activity on the job. One example is to manage on-the-job rest intervals more carefully. Another potential intervention strategy is to encourage moderate intensity physical activity outside of work to improve worker fitness and, ultimately, potentially improve their ability to perform physical activity on the job with less strain.

How does physical activity on the job during pregnancy impact health?

Evidence of the health benefits of leisure-time physical activity extend to pregnancy and the post-partum period. As such, the Physical Activity Guidelines for Americans, second edition recommendations for at least 150 minutes of moderate intensity activity per week applies during and after pregnancy, with the provision that pregnant individuals consult their healthcare provider for personalized guidance on whether or how to adjust activity levels. As noted above for the general workforce, there is some evidence suggesting that exposure to some types of physical activity on the job during pregnancy may be associated with detrimental health effects.

More than 50% of American women remain employed full-time during pregnancy. For many pregnant workers, physical activity on the job is a major component of their total physical activity.¹⁵ Prior research that includes some systematic reviews with meta-analyses suggest that exposure to physical work activity during pregnancy, such as prolonged standing and lifting objects weighing more than 22 pounds (10 kg), may be associated with adverse maternal health and pregnancy outcomes, including musculoskeletal conditions such as functionally limiting pelvic girdle pain,^16,17 hypertension disorders and preeclampsia,^18,19 miscarriage, and preterm delivery.^20,21

The evidence examining associations between physical activity at work during pregnancy and cardiovascular outcomes such as hypertensive disorders and preeclampsia is more limited than for pregnancy outcomes. And the recent study of 257 pregnant workers, which was described in the webinar, is novel in being the first to report the independent and joint associations of physical activity on the job and leisure activity with a known risk marker for cardiometabolic health (high-sensitivity C-reactive protein known as hs-CRP).²² This is a marker for inflammation that may be involved in development of cardiovascular disease. Physical activity on the job was associated with higher levels of this risk marker. Leisure activity has been shown to be associated with lower levels of this marker in prior research.

More research on the relationship between physical activity at work and health is needed in the general workforce, including among pregnant and older workers who may be more susceptible to adverse health effects. Accordingly, the physical activity health paradox is a topic deserving additional research attention and that may warrant further exploration in the next physical activity guidelines development process.

Resources for employees and employers to help reduce the potential adverse effects of physical activity on the job:

• The CDC has various workplace health resources* including information on
  • reducing stress among employees
  • screening for cardiovascular disease and referral by small worksites
  • providing strategies to prevent heart attack and stroke in the workplace

*Please note that these CDC resources do not mention the physical activity health paradox hypothesis and do not provide any information on the potentially adverse health effects of physical activity on the job.

• NIOSH has resources on understanding the risks of physical demands and recommendations for safe lifting to reduce risk of musculoskeletal disorders, including
  • The “Applications Manual for the Revised NIOSH Lifting Equation” which provides recommendations for safe load weight, size, location, and frequency of handling to reduce the burden on workers.
  • Information related to reproductive health and physical job demands.
• Additionally, provisional guidelines for lifting during pregnancy based on the Revised NIOSH Lifting Equation are available.¹⁴

To learn more about NORA’s Cancer, Reproductive, Cardiovascular, and Other Chronic Disease Prevention (CRC) cross-sector council, please send an email to crcprogram@cdc.gov

Taylor Shockey, PhD, MPH is a research health scientist in the NIOSH Division of Field Studies and Engineering

Tyler Quinn, PhD is an assistant professor in the Department of Epidemiology and Biostatistics at West Virginia University’s School of Public Health

Liwei Chen, MD, PhD is an associate professor in the Department of Epidemiology at University of California Los Angeles (UCLA) Fielding School of Public Health

Niklas Krause, MD, MPH, PhD is a professor emeritus in the Departments of Epidemiology and Environmental Health Sciences at University of California Los Angeles (UCLA) Fielding School of Public Health

References

1. Quinn T and Gibbs BB. Context matters: The importance of physical activity domains for public health. Journal for the Measurement of Physical Behaviour. 2023. https://doi.org/10.1123/jmpb.2023-0030
2. Holtermann A, Hansen JV, Burr H, SØgaard K, SjØgaard G. The health paradox of occupational and leisure-time physical activity. Br J Sports Med. 2012;46:291-295. https://doi.org/10.1136/bjsm.2010.079582
3. Holtermann A, Krause N, van der Beek AJ, Straker L. The physical activity paradox: six reasons why occupational physical activity (OPA) does not confer the cardiovascular health benefits that leisure time physical activity does. Br J Sports Med. 2018;52(3):149-150. https://doi.org/10.1136/bjsports-2017-097965
4. Coenen P, Huysmans M, Holtermann A, Krause N, van Mechelen W, Straker L, van der Beek A. Do highly physically active workers die early? A systematic review with meta-analysis of data from 193,696 participants. Br J Sports Med. 2018;52(20). https://doi.org/10.1136/bjsports-2017-098540
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