Question: A previous post ([What Is Energy? Where did it come from?](https://physics.stackexchange.com/q/3014/)) defines work qualitatively as "a process in which energy is transformed from one form to another form". And mathematically, work is defined as:

$$\Delta KE=\int\_{C} \vec{F}\cdot\mathrm d\vec{r}$$

But if you imagine lifting up a rock from the ground at constant speed, am I not doing work on the rock by converting the chemical energy stored in my muscles into the potential energy of the rock? I am confused because the kinetic energy of the rock does not change and yet I am still converting energy from one form to another, which is the qualitative definition of work. What's the right way to think about this and the concept of work in general?

Answer: 
The problem with work is the word we use for it. Since we work everyday, we're used to associate "physical work" and "effort", and that's confusing.

Physical work is a well defined quantity, but it needs 3 surnames, and this is usually omitted. You must specify these three parameters:

Work done [by some force] [on some system] [along this path]
------------------------------------------------------------

Note how deep is this sentence. Work is done by forces, not by people. You don't do work, a force does work, not you.

Plus, work must be considered on a system. If you lift a rock, you are doing possitive work on the rock. However, gravity is doing negative work on the rock.

$W\_{you}=mg\cdot h\cdot 1$; because $cos(0º)=1$

$W\_{gravity}=mg\cdot h\cdot -1$; because $cos(180º)=-1$

So the total work on the rock is $0$ and that's why you are not increasing its kinetic energy. If you perform extra forces, then you will accelerate teh rock ($F=ma$, you know). So you'll accelerate the rock and hence the KE changes. It makes sense.

But you have to realize that you are considering the rock as a well delimited system. If you include the chemical energy stored in your arms, then your system under consideration is not the rock alone anymore. Your new system under study will be the rock-person system, and then you have to consider ALL forces involved in that system, not just your arm.

In conclusion: work needs 3 specifications. You seem to be needing to focus on the "on what system" part.

Hope this helped
I think maybe you are confused by an example that is often given to emphasize that the physics definition of "work" doesn't always match how it is used in everyday speech. If you move a rock *horizontally* at constant speed, then you are doing no work on the rock. Its kinetic and potential energy are both the same through the whole process. This is a common example because it certainly feels like you are doing work, and that is because maintaining constant tension in your muscles takes energy, which is converted into heat. Individual cells contract and then get tired and loosen up; you can't just lock your muscle at a certain length.

But lifting a rock upward is different, even if the velocity is constant. Then you really are doing work on it in the physics sense, because you are converting chemical energy to gravitational potential energy.