Credit: Adobe Stock/Supachai.
Many jobs require workers to be on their feet for long periods of time, such as nurses moving from patient to patient, retail staff stationed at a service counter, hairdressers with back-to-back appointments, or machine operators hooked up to a production line. Commonly reported at the end of these shifts are stiff necks, back pain, and leg pain, which are well known in the occupational health field. However, the hidden consequences that unfold higher up are less visible.
Working in an upright position for long periods of time can put a strain on the circulatory system, and in some cases can affect the brain and its blood supply. The most striking examples make headlines. For example, the members of the House of Lords passed out after standing motionless in their heavy military uniforms under the summer sun at Buckingham Palace. Similar collapses occur during military parade training (“parade fainting”), among choir members standing under hot stage lights, and even during graduation ceremonies. These dramatic events represent the extremes of a widespread cyclical stress continuum. The same mechanisms that cause fainting (or syncope) in ritual settings continue to operate in many workplaces, but in a more subtle way.
Physiological function when standing up
When a person assumes an upright position, gravity pulls approximately 500 to 800 mL of blood downward into the flexible veins of the legs and visceral (abdominal) area. This redistribution reduces the amount of blood returning to the heart and lungs, forcing the body into a compensatory state. In particular, your heart rate increases, your breathing deepens, and your blood vessels tighten to prevent a drop in blood pressure and oxygen supply. Typically, the magnitude of these responses varies depending on the degree of circulatory stress imposed by the upright position.
Even if these compensatory responses are able to maintain blood pressure and oxygen levels within normal limits, cerebral blood flow may still be reduced. Doppler ultrasound studies in healthy adults have shown that continued upright posture can reduce total cerebral blood flow by approximately 6% within 30 minutes. While this change may seem modest in itself, when combined with real-world stressors such as high cognitive demands, psychological stress, and sleep deprivation, the effects can quickly multiply. Heat and dehydration further exacerbate the problem. Heat dilates blood vessels in the skin, while dehydration reduces total circulating blood volume, drawing blood away from the central circulation that supplies the brain. Laboratory models that exaggerate blood retention, such as negative body pressure or prolonged heat exposure, as well as patient cohorts with orthostatic intolerance, typically show a clear pattern, with increased circulatory strain associated with decreased cognitive performance. These changes often occur in parallel with a decrease in cerebral blood flow and oxygenation. It is important to recognize that the work environment can also reproduce the same cyclic stress pathways seen in controlled clinical examinations.
What this means for safety and performance
In safety-critical tasks, “small” cognitive changes are not small. A modest posture-related reduction in cerebral blood flow or oxygen supply can be enough to tip attention, working memory, and executive function in the wrong direction at exactly the wrong moment. This is particularly relevant for continuous monitoring tasks, operating equipment, driving, patient care, or any role where small delays can accumulate and result in errors.
Although most workers are not exposed to the extreme postural stress that leads to fainting, they are still subject to a cycle of cyclic stress. Rather, more common consequences include increased fatigue, brain fog, decreased reaction time, and poor decision-making, all of which can cascade into completely preventable mistakes in the workplace. Recognizing the importance of the risk of cyclic stress during prolonged upright work, there is a need to implement monitoring, prevention, and remedial strategies in relevant workplaces to protect workers’ brains.
Monitoring circulatory stress in an upright position
Monitoring doesn’t have to be complicated, but it does need to be effective. Understanding typical and atypical physiological responses to posture-related cyclic stress can help organizations design monitoring programs that meaningfully reflect risk. Although direct measurements of cerebral blood flow provide the most specific insight, measurement tools such as transcranial Doppler ultrasound are not yet practical for routine use in the workplace. Instead, circulatory stress can be monitored through relevant and accessible indicators such as blood pressure and heart rate.
One of the most beneficial approaches is the active stand test. After 5 minutes of rest in a seated or supine position, blood pressure and heart rate are measured using an automatic upper arm cuff and repeated 1 and 3 minutes after standing. A decrease in systolic blood pressure of more than 15 to 20 mmHg (top number) or diastolic blood pressure of more than 7 to 10 mmHg (bottom number) indicates orthostatic hypotension, which reflects the strain on the circulatory system and reduced ability to maintain an adequate blood supply to the brain. Conversely, your heart rate may increase rapidly even though your blood pressure remains stable. An increase in heart rate, typically greater than 27 to 30 beats per minute, suggests a compensatory but strained cardiovascular response. These reactions can be accompanied by symptoms such as dizziness, light-headedness, and blurred vision, but objective markers are valuable because reporting symptoms is subjective and often underrecognized or underreported. Incorporating simple cognitive tests (e.g., n-back, Stroop) into active stands can reveal deficits in attention and executive function that may appear during postural stress. There are many studies showing that cognitive tests can distinguish between healthy people and people with postural/orthostatic intolerance. Although universal performance cutoffs have not yet been established, quantifying individual baseline responses under optimal conditions (e.g., rest, adequate hydration, temperate environments) allows relative changes to be meaningfully tracked over time.
A common criticism of active stand testing is the amount of time it takes. A proper assessment requires 5 minutes of rest and 3 minutes of standing. Moving to a more continuous monitoring strategy may become more practical for daily use. Portable blood pressure monitors automatically record upper arm measurements every 15 to 30 minutes and provide valuable trend data, but require the worker to hold the arm still for 30 to 60 seconds during each inflation cycle. This interruption pattern may be impractical for many types of jobs and can make arm cuffs uncomfortable for an entire shift. Therefore, outpatient monitoring is more suitable for temporary evaluation than routine use. A useful alternative is heart rate wearables, such as smart watches and rings, which are small, discreet, and great for continuous monitoring. These are good for identifying trends such as upward drift in heart rate across a work shift or differences between tasks or environmental conditions. Accuracy varies by device and level of movement, but advances in technology and motion-gated sampling (e.g., using built-in accelerometers to take readings only when limb movement is minimal) have significantly improved data completeness. Most devices require only very short periods of quiescence to take reliable snapshots throughout the day.
Regardless of the tool used, it is important to remain focused on the core objective of monitoring fatigue and cognitive decline. However, simply monitoring these indicators does not explain the cause of the failure. Combining circulation indicators with fatigue and cognitive performance indicators can help determine whether circulation is to blame for changes. If not, there may be reason to evaluate other factors, such as sleep deprivation, circadian rhythm disturbances, psychological stress, workplace distractions, nutritional deficiencies, and mental health issues. Understanding the physiological underpinnings of fatigue and cognitive decline allows organizations to select the most appropriate preventive and remedial strategies, ensuring interventions target the appropriate mechanisms underlying the symptoms.
Evidence-based strategies to reduce posture-related cyclic stress
The most effective interventions are those that interrupt prolonged upright posture before fatigue, cognitive decline, or presyncope symptoms occur. In practice, this means treating prolonged upright positioning as an exposure that should be avoided as much as possible outside of working hours. The basic idea is to avoid standing upright for long periods of time by incorporating a variety of postures into your tasks. This includes alternating between standing, walking, and sitting, and scheduling frequent recovery opportunities. The evidence supporting the “microbreak” approach is strongest when breaks are frequent and include at least some light movement. In the case of posture-related circulatory stress, short movements that recruit leg and hip muscles improve venous return via muscle pumps and help restore central blood volume.
A complementary low-cost strategy is to train workers to use muscle pumps intentionally throughout the day. Physical counterpressure maneuvers, such as tightly tensing the buttock/thigh muscles and crossing the legs or raising the calves, immediately improve venous return and support circulation. These maneuvers are particularly useful because they can be deployed in real time without tools or supervision and can be practiced until they become automatic safe behaviors. Allowing short recumbent or semirecumbent recovery positions, as work permits, is a powerful method to restore central blood volume when upright tolerance is exceeded. In many workplaces, this is as simple as having a nearby space where employees can safely sit or lie down without stigma or punitive pressure. Environmental and hydration management is also important, as heat and dehydration amplify the same circulatory stress mechanisms caused by upright posture. Actual controls include heat mitigation (ventilation, shade, work/rest cycles) and reliable access to fluids. For example, drinking 500 mL of water has been shown to improve orthostatic tolerance within 5 minutes.
Finally, mechanical circulatory support may be appropriate for workers in high-risk roles or with recurrent symptoms. Compression strategies that involve the abdomen and legs (such as compression stockings, abdominal binders, and inflatable compression devices) can target large veins where blood tends to pool during prolonged postural stress. While comfort and adhesion must be considered, these supports can reduce fluid retention and improve upright tolerance. New technologies such as dynamic compression, which adjusts compression support in response to changes in posture, are particularly promising as they may be better suited to real-world variations in job demands and environmental stressors.
Working upright for long periods of time is usually treated as a musculoskeletal problem, with attention given to stiff necks, back pain, and leg pain. But this perspective is only part of the story. Upright posture also imposes an often-overlooked circulatory stress that can subtly reduce blood flow to the brain, leading to fatigue and cognitive decline over time. Visualizing this hidden physiology opens new avenues for the prevention and management of these risks, an important step towards a safer workplace.
Anthony Incognito is an assistant professor in the Department of Biomedical Sciences at the Memorial University of Newfoundland Faculty of Medicine.