New Updates On The Effects Of Prolonged Sitting

All on screens while sitting

I first wrote about the ill effects of sitting or being an active couch potato back in 2014. Subsequently, there were more and more research about the negative effects of prolonged sitting, suggesting that sitting is the new smoking. There were also suggestions that not all sitting is bad.

Previously, most of the data suggested that these effects were independent of your exercise habits. Even the fittest people were at risk of heart disease if they spent large amounts of their time sitting in front of desks or watching television.

Now, this is not prolonged sitting

One suggested reason why prolonged sitting is bad is that there is reduced blood flow to your legs. Your blood vessels become stiffer and less able to expand and contract in response to changes to your blood flow. Over time, that makes you more prone to atherosclerosis - a hardening and narrowing of your arteries, leading to heart disease.

Time for an update. New published research from Japan (Morishima et al, 2020) suggests that endurance training might well have some protective effects. There seems to be some differences between the current and previous study.

In the current study, the researchers studied a group of competitive cyclists versus a control group that did no endurance exercise. Before exercise and three hours later, there is almost no change in the blood flow to the legs of the competitive cyclists while it dropped by half in the matched controls.

Previously, another recent study by Garten et al (2019) that showed that endurance exercise had no protection for trained athletes. If you examined the data more carefully, you will notice that the "trained" group had an V02 max of around 50 ml/kg/min. This level is above average for young adults but not fantastic.

Nah, I'm not one of the cyclists in that study

In the latest study by Morishima by et al (2020), the competitive cyclists had an average V02 max of 61 ml/kg/min. This is considered excellent, and they have been training for five years and rode an average of 600 km per week.

The earlier study assessed micro vascular function in the subjects. This refers to the function of smaller arteries that branch off the big arteries and go into the muscles. The current study measured macro vascular function, this is the function of the big arteries from the heart to various parts of the body.

Both forms of vascular function are important. The responsiveness of the big arteries predict your risk of atherosclerosis, while the smaller arteries dictates how quickly and effectively oxygen rich blood goes to your muscles. This is really important for all athletes.

Possibly this may suggest that all the endurance training at a high level protects you from macro vascular function, but not micro vascular function during prolonged sitting. This is good news for your long term health.

However more specific research is needed, so train hard and at the same time try not to sit too long at work or at home watching Netflix. Hopefully with the circuit breaker ending in a few days time, you'll get out to exercise more often.

References

Garten RS, Hogwood AC et al (2019). Aerobic Training Status Does Not Attenuate Prolonged Sitting-induced Lower Limb Vascular Dysfunction. App J Physiol Nutr Metab. 44(4): 425-433. DOI 10.1139/apnm-2018-0420.

Morishima T, Tsuchiya Y et al (2020). Sitting-induced Endothelial Dysfunction Is Prevented In Endurance-trained Individuals. Med Sci Sp Ex. DOI: 10.1249/MSS.0000000000002302.

Great day to go cycling - Mount Faber