Newsletter #176: The Impact of Sitting vs Standing 🪑
Hey humanOS friends! So, obviously we like to talk about physical fitness and exercise. But this week we took a serious look at research examining the health impact of replacing time spent sitting down with much more subtle forms of physical activity, like standing.
You probably don’t really think of standing as activity, per se, but upright posture is maintained through muscle contractions, and these tiny muscle movements actually do have a cumulative impact on your health. For example, standing promotes the translocation of GLUT4, a protein that helps shuttle circulating glucose into your muscles (rather than letting it hang around in your bloodstream). This, in turn, lowers blood sugar and boosts insulin sensitivity, which is a very good thing. Interestingly, this may not only apply to standing - even just squatting down on the ground or fidgeting your leg may have a similar effect.
This, obviously, is relevant for a lot of us, because the average office worker spends almost six hours a day sitting at their desk, and some research suggests that just working out may not fully cancel out the negative effects of sedentary behavior. To learn more, scroll on down 👇🏼
This Week’s Research Highlights
🪑 Hunter-gatherers have similar inactivity levels to us - but how they rest may be the big difference.
Abundant research shows that prolonged periods of inactivity is linked to increased cardiovascular disease and mortality risk. To observe how sedentary behavior occurs in an ancestral environment, researchers examined physical activity and inactivity patterns in the Hadza, a hunter-gatherer population in Tanzania (the region of the world where it is thought that anatomically modern humans evolved). They equipped the Hadza participants with accelerometers to objectively measure their movement, and found (unsurprisingly) that the Hadza were extremely active, engaging in levels of moderate-to-vigorous activity more than three times the amount advised by US Department of Health and Human Services.
However, they also spent about the same amount of time being sedentary as people in industrialized countries - without appearing to suffer the same consequences of inactivity that we do. How come? Using electromyography (EMG), the researchers measured muscle activity used in common resting postures observed at the camp, such as squatting and kneeling, and found that there was significantly more muscle activity in the lower limbs during these postures, compared to sitting in a chair. In fact, the muscle activity in squatting and assisted squatting postures rose to ∼20–40% of walking values for some muscles, pretty similar to that of standing. So, perhaps inactivity itself is not evolutionarily novel, but rather the mismatch lies in how humans in the industrialized world choose to rest, following the invention of chairs.
🧍🏽♀️ Standing is independently associated with markers of insulin sensitivity.
Researchers measured sedentary time, standing time, and physical activity in sedentary adults with metabolic syndrome (n=64) using accelerometers. They also measured insulin sensitivity in subjects using the hyperinsulinemic-euglycemic clamp technique - the gold standard for assessing insulin sensitivity in humans - as well as insulin and insulin resistance (HOMA-IR). After analyzing the data, they found that sedentary behavior, standing, steps, and VO2 max were all associated with insulin sensitivity, HOMA-IR, and insulin levels. However, after adjusting for body fat percentage, only standing was still linked with HOMA-IR and insulin, and this association was still significant after adjusting for sedentary behavior, physical activity, and physical fitness.
🚶🏻♂️ Substituting some daily sitting time with standing and walking can result in striking improvements in cardiometabolic risk markers.
In a crossover study, 24 sedentary overweight/obese participants followed two activity regimens, each four days in duration. One, “Sit,” involved sitting for 13.5 hours, standing for 1.4 hours, and light-intensity walking for 0.7 hours per day. The other, “SitLess,” prescribed 7.6 hours of sitting, 4 hours of standing, and 4.3 hours of light-intensity walking. After the “SitLess” activity regimen, bloodwork revealed that the AUC (0-190 minutes) for insulin had decreased by 20%, insulin sensitivity improved by 16% (measured by Matsuda index), fasting triglycerides decreased by 32%, non-HDL cholesterol dropped by 7%, apoB lowered 4%, and HDL cholesterol increased by 7%. Diastolic blood pressure was also lower after “SitLess” compared to “Sit.”
🦵 Even just fidgeting your leg can improve postprandial glycemic control.
Twenty adults with obesity participated in a randomized crossover trial in which they were given an oral glucose load, and then sat for three hours. During sitting, participants either remained stationary, or they intermittently fidgeted both legs (2.5 minutes on, 2.5 minutes off). When the subjects fidgeted, blood flow through the popliteal artery in the leg increased (as you would tend to expect), oxygen consumption rose by ~20%, and fidgeting lowered both glucose and insulin AUC. As with the aforementioned studies, this effect is likely due to repeated muscle contractions and boosted skeletal muscle blood flow. Although if you decide to embrace fidgeting as a strategy for metabolic health, watch out because you might annoy a significant portion of people around you. 👀
Random Trivia Question of the Week
🤔 Research from Stanford found that people in the US get an average of 4774 steps daily. When researchers equipped members of the Old Order Amish with pedometers to gain insight into their physical activity patterns, the results were...quite different. How many steps do they get per day?
💡 ANSWER
Podcasts We Loved This Week
- Matt Kaeberlein: The biology of aging, rapamycin, and other interventions that target the aging process. Via Peter Attia.
- Tharick Pascoal: Is inflammation in the brain causing Alzheimer’s disease? Via Science Friday.
Products We Are Enjoying
Standland
If you are trying to get up out of your office chair more, maybe gamifying the process can help.
Standland can track your standing time either via your Apple Watch or your iPhone (not sure if it is available for Android yet), and as you meet certain standing achievements you gain access to various cute creatures, like an owl, a rabbit, a chicken, etc.
Aside from the pet collection, the app also provides pretty impressive weekly and monthly reports on how much you’re standing and how you’ve improved over time.
humanOS Catalog Feature of the Week
Thank you so much for reading, and see y'all next week!