Muscle Inactivity Behind the Health Risks of Excess Sitting

YOU’VE PROBABLY heard that excessive sitting is considered an independent risk factor for many chronic conditions, including heart disease. As we put it last year, sitting is the new smoking. You’ve probably also heard that the link between too much sitting and worse health is true even for people who work out regularly.

What you may not have heard is what exactly makes sitting so dangerous. The answer may be too much muscle inactivity, suggests new research published in Medicine & Science in Sports & Exercise.

Finnish researchers had 150 adults wear shorts that measured muscle activity in their thighs and hamstrings while the participants went about typical weekdays. Muscles were said to be inactive if they registered lower electromyographic amplitude than when standing still. Moderate to vigorous activity was defined as producing an amplitude greater than when walking at a pace of 5 kilometres per hour.

Even though the participants were fit and active, their hamstrings and thighs were, on average, inactive for 65 percent of their waking days. That is, for almost two-thirds of the time the participants were awake, some of the largest muscles in their body were less active than if they were standing still.

The researchers then divided the participants into four groups, from lowest to highest amount of muscle inactivity. Compared to those with the least amount of inactivity (55 percent or less of the time), those with the most muscle inactivity (at least 74 percent of the time) had significantly worse HDL cholesterol and triglyceride readings. This was true independent of the amount of time spent in the study’s definition of moderate to vigorous physical activity.

One common piece of advice is to take frequent breaks from sitting. This study offers insight into an easy way to do so: Standing from a sitting position produced enough muscle activity in the thighs to get above the threshold found to be linked to worse cholesterol readings.

“These results give further support for the message ‘stand up, sit less, move more’ to promote metabolic health as a complement to current exercise guidelines,” the researchers wrote.

Related Articles