As is the case for many occupations today, the life of a student isn’t always a particularly active one. While some of us manage trips to the Plex or take runs around the Reservoir, in reality, getting to work generally means being tethered to a table in O’Neill staring at a computer. This situation can get especially desperate during midterms week, when our physical activity is limited to quick trips to Lower for dinner, or the bold decision to face the million dollar stairs rather than shortcutting through the Maloney elevators.
While this type of sedentary behavior can be good for your GPA, research has shown that it’s not good for your health. Spending excessive time seated leads to a significant reduction in blood flow through the legs, known as endothelial dysfunction, and decreased arterial wall shear stress, which is a measure of the drag of blood moving past artery walls. These effects have various consequences both in the short and long term on health. In the short term, this leads to reduction in artery radius, blood clots, and apoptosis of endothelial cells (Morishima, Zhuang). In the long term, it is linked to obesity, type 2 diabetes, and an increased risk for cardiovascular disease. In fact, the risk of mortality due to cardiovascular disease triples for those who spend a great deal of time in a sedentary position when compared to those whose daily sitting time is lower (Weller). Of course, desk jobs and sedentary work cannot be easily abandoned on a large scale. Instead, exercise physiology researchers led by Dr. Jaume Padilla at the University of Missouri, Columbia decided to look for a more realistic solution to endothelial dysfunction.The results found that the routine, subconscious human behavior of fidgeting can help fight against this common disease.
To establish the link between fidgeting and blood flow in the legs, the researchers recruited eleven healthy student subjects, whose blood velocity and artery diameter were measured using ultrasound technology after 10 minutes of rest. The subjects were placed in a seated position for 3 hours, during which time they were instructed to fidget intermittently (one minute of fidgeting after every four minutes of leg stillness). Only one leg was allowed to fidget, while the other served as a control. “Fidgeting” in this experiment was either bouncing of the knee or tapping of the heel, and the rate of fidgeting was roughly the same in all subjects. Blood flow and artery shear rate were measured at regular intervals throughout the experiment, and flow-mediated dilation (FMD) in the legs was measured at the beginning and the end (Morishima). A slow FMD response is indicative of endothelial dysfunction, so FMD measurements could show whether fidgeting was healthy for the legs (Kelm).
Interestingly, the simple act of fidgeting made a big impact on subjects’ endothelial function. Although both blood flow and shear rate were reduced in both legs as a result of the sitting period, the fidgeting leg maintained a relatively higher blood flow and shear rate than the control leg during and directly after the experiment. In measurements taken immediately after fidgeting, the artery shear rate in the fidgeting leg was roughly five times greater than that of the control, indicating that blood flow was elevated. As the time since fidgeting increased, the artery shear rate in the fidgeting leg decreased once more to match the control leg. Still, at the end of the three-hour sitting period, subjects’ FMD had either improved or stayed the same in the fidgeting leg. In contrast, the leg that was left completely still showed a significant decline in FMD. Fidgeting also helped prevent the increase in ankle circumference experienced by the control leg as a result of obstructed blood flow (Morishima).
While It is still unknown exactly how prolonged sitting reduces shear stress and FMD, it is clear that even limited amounts of movement (such as fidgeting) can help prevent this impairment. Becoming more familiar with these mechanisms could shed more light on ways to avoid, and heal endothelial dysfunction in the legs. Still, since a small amount of fidgeting improved blood flow and prevented endothelial function from being degraded, the researchers concluded that people should make a conscious attempt to fidget when sitting in one position for extended periods of time (Morishima). Simple bouncing of the knee works, but there are many ways to build on this idea: find some simple leg exercises to run through while sitting in class, or move your feet to music in your headphones while working in the library (just don’t start singing along). Even better, take frequent breaks to walk around and stretch your legs, or turn your dresser into a makeshift “standing desk.” The healthiest options for our endothelial system involve standing up and being as physically active as possible. However, during finals week or the night before you have a big paper due, it is important to remember that small movements performed in place can have a big effect on our bodies.
- Kelm, Malte (2002). Flow-mediated dilatation in human circulation: diagnostic and therapeutic aspects.
- American Journal of Physiology – Heart and Circulatory Physiology Published 282, 1-5.
- Morishima, Takuma et. al (2016). Prolonged sitting-induced leg endothelial dysfunction is
- prevented by fidgeting. American Journal of Physiology – Heart and Circulatory Physiology 311, 177-182.
- Zhuang, YJ et. al (1998). Sequential increases and decreases in blood flow stimulates progressive intimal thickening. European Journal of Vascular and Endovascular Surgery 310, 10.
- Weller I, Corey P (1998). The impact of excluding non-leisure energy expenditure on the relation between physical activity and mortality in women. Epidemiology 9, 632 –635.