A some­what seden­tary lifestyle com­bined with reg­u­lar exer­cise is turn­ing us into what phys­i­ol­o­gists are call­ing ‘active couch potatoes’–and that exer­cise, no mat­ter how vigourous, doesn’t appear to be coun­ter­act­ing the neg­a­tive effects of that seden­tary lifestyle.

In rats, this lifestyle was found to pro­duce “unhealthy cel­lu­lar changes in their mus­cles” and increase insulin resis­tance and fatty acid lev­els in their blood. In con­clu­sion: a mostly seden­tary lifestyle is bad for us, regard­less of exer­cise habits.

[Stud­ies have shown] that, to no one’s sur­prise, the men who sat the most had the great­est risk of heart prob­lems. Men who spent more than 23 hours a week watch­ing TV and sit­ting in their cars (as pas­sen­gers or as dri­vers) had a 64 per­cent greater chance of dying from heart dis­ease than those who sat for 11 hours a week or less. What was unex­pected was that many of the men who sat long hours and devel­oped heart prob­lems also exer­cised. Quite a few of them said they did so reg­u­larly and led active lifestyles. The men worked out, then sat in cars and in front of tele­vi­sions for hours, and their risk of heart dis­ease soared, despite the exer­cise. Their work­outs did not coun­ter­act the ill effects of sitting. […]

Decades ago, before the advent of com­put­ers, plasma TVs and Room­bas, peo­ple spent more time com­plet­ing ‘light-intensity activ­i­ties’ […] Nowa­days, few of us accu­mu­late much light-intensity activ­ity. We’ve replaced those hours with sitting.

The phys­i­o­log­i­cal con­se­quences are only slowly being untan­gled. […] Sci­en­tists believe the changes are caused by a lack of mus­cu­lar con­trac­tions. If you sit for long hours, you expe­ri­ence no ‘iso­met­ric con­trac­tion of the anti­grav­ity (pos­tural) mus­cles’. […] Your mus­cles, unused for hours at a time, change in sub­tle fash­ion, and as a result, your risk for heart dis­ease, dia­betes and other dis­eases can rise.

via Waxy