A friend of mine and I were talking and the question came up whether someone who is standing burns more calories than someone who is sitting. I said that of course the person standing is burning more calories since it takes work to stand upright for long periods of time.
For example, I notice my leg muscles start to ache when I have to stand for an hour or two. My friend said that standing doesn’t require any additional effort since your legs are locked and your bones are carrying the weight, not your leg muscles.
So who is right? Does standing burn more calories than sitting, or is it roughly the same?
I don’t have a cite, but I can say that your friend is clearly wrong. No one stands perfectly still with their legs locked. Just watch someone (or yourself) the next time you’re “standing still.” You’ll shift your balance, move your feet, edge forward or back, etc. The movement is almost constant.
I’d argue whether humans can really lock their legs at all; I’m pretty sure that some muscular tension is necessary to keep them locked.
Considering that one always hears that sitting is bad for you, but not standing, there must be something about sitting, like decreased caloric expenditure, that makes it unhealthy. Indeed, this article claims that standing burns 50% more calories than sitting, which is a pretty big difference (although, sitting is supposedly bad even if you try to exercise it off so there is more to it than that).
The difference is probably very slight (assuming your standing still). But yes, it definitely takes more energy to remain standing for a given period of time than to sit. Your heart has to work harder, your leg muscles have to support your weight, your core has to keep your middle straight up, and your everything has to constantly shift around to maintain balance.
Some people do lock their knees, and it does feel like it reduces the energy required to stand. However, it can transfer tension in the back of the leg to the top of the hip, using the piriformis muscle - through or under which the sciatic nerve passes. This may cause inflammation of the muscle, and thus pressure on the sciatic nerve, and thence, sciatica (a painful condition of the hip and lower back).
I used to have piriformis muscle syndrome (i.e. sciatica caused specifically by the piriformis muscle) really badly. I had a 3 hour drive home at the end of the week, and two of those hours were agony. I could barely sit at a desk during the day.
Then my gym instructor pointed out that I always stood with my knees locked back - a habit I have had for years, and relates to the hypermobile joints I suffer from. With her yelling at me whenever she saw me do it and motivated by the pain in my hips, I have learned to stand with my knees in a more natural slightly bent condition. And I don’t have problems in my hips any more (I had better not, I am going on holiday driving round southern europe shortly). It has made a real difference, and I am finally at the stage where I feel wrong if my knees are locked back, and I don’t do it very much at all.
Possibly one reason why sitting might be worse for health (back health, at least) is that most people slouch like mad when sitting for a long time.
Keeping balance definitely uses energy (and is work), even though it’s a small amount of energy / work.