I'm holding a bag with some mass $m$. The force required for not letting it fall is equal to its weight $m \cdot g_L$ (where $g_L$ is the local gravity, assuming Earth this is $\approx 9.8 \; \text{m} \text{s}^{\text{-1}}$).
Now, in order to create and maintain a such force, ATP molecules (in my muscle cells) have to bind to myosin releasing its actin, ADP and some energy from the bond. This energy is then used to contract the muscle cell. Though no energy is putted into the bag (as its potential energy does not increase nor decrease) my muscles must still hydrolyse ATP in order create that energy needed to contract. This energy is in the end released as heat.
Now, my question is: how much energy – or rather power – is needed to maintain my bag in place counteracting gravity? Now human muscles aren't perfect so to avoid any complicated biology I simply want to know how much power it would take, assuming no losses and a perfect system.
