Now Sitting Bull was the famous Native American chief who defeated General Custer at the Battle of Little Bighorn. But that’s not what I’m going to talk about here. Take this quote for example from ABC Australia and Professor Marc Hamilton, a researcher into the dangers of “sitting”.
“The studies show sitting for long periods can be dangerous to health, even when people exercise regularly, increasing the risk of heart disease and other conditions by 80 per cent.”
And . . .
“Even people who are lean are at risk for this, so we’re not immunised by being lean and exercising and eating a healthy diet.”
One would think that sitting is an absolute risk factor for heart disease and related conditions like diabetes, but is this so?
There is no doubt that in population studies (Healy et al), sitting for long periods is associated with an increase in cardio-metabolic risk factors like inflammation, waist circumference, triglycerides and insulin resistance. I understand that public health authorities and advisers and researchers in the scientific community need to get a simple message across — which is that we need to move more for metabolic health and fitness, and that sitting, especially for long uninterrupted periods, may work against this. What I don’t buy is that sitting is a primary risk factor and that even if you exercise and stay lean, your risk of heart disease and associated conditions is increased with prolonged sitting — independent of the formal and proven metabolic risk factors, which is what the spiel on this subject, above, implies.
Here’s a theoretical case study. An amateur triathlete and ‘weekend warrior’ likes to compete in weekend triathlons . . . nothing too serious but he has to be fit to get around the 1500 metre swim, 40 k bike and 10 k run. He’s 40 and works as an IT consultant, often sitting for 6 to 8 hours/day. He trains for about an hour a day, six days a week, sometimes a little more, mixing swimming, cycling and running. He’s very fit, but he’s not exactly an elite athlete, and he mirrors what many men and women do in their recreational hours to keep fit and healthy. His diet is pretty good as well.
On the metabolic and cardiorespiratory front he has a total cholesterol of 4.5 mmol/L (175 mg/dL), fasting triglycerides of 1.0 mmol/L (88 mg/dL), fasting glucose of 5 mmol/L (90 mg/dL). His body fat is 10 percent. His resting heart rate is 50, his heart rate reserve is 140. His VO2 max is 62. This guy is at increased risk of heart disease because he sits at his job all day? I don’t think so.
My triathlete is theoretical, but I know the numbers are close because I’ve been there, done that, and trained with amateur triathletes, fun runners and marathoners. Even so, others will do much worse (and some will do even better) for these metabolic parameters, even with strong exercise regimens. Yet the proof is surely in the pudding: sitting is not a primary risk; the metabolic numbers are what counts. Get them right and you can sit until the cows come home. The message regarding being sedentary, of which sitting is part, needs to be put more qualitatively and . . . well . . . quantitatively regarding physical activity. Or else show me the proof.
Healy GN, Matthews CE, Dunstan DW, Winkler EA, Owen N.Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003-06. Eur Heart J. 2011 Mar;32(5):590-7.