Do adjacent sarcomeres oppose each other during contraction? A sarcomere is the contractible portion of the muscle cell. And here is a figure of three sarcomeres in series before and after contraction:

I was taught that the thick fiber, myosin, pulls on the thin fiber, actin. I am confused as to how contraction can happen because it seems that there is a tug of war going on between myosins on either side of the Z-line.
Is there another force vector I am not accounting for? Or is there some additional biophysics going on that I am not aware of?
Edit: I guess it could all contract if the outermost sarcomeres had a weaker opposing tension than the internal tension. But it would start from the outside and radiate in. In other words, there would be a gradient of contraction with the shortest (most contracted) to longest from outside to inside until all are equally contracted. I'm not sure if that's how it works in reality.
 A: Disclaimer: I am not a specialist, but reading about it, this is what I understand:
I don't think a tug of war happens. All the Z disks and M lines are not fixed but can move out of their resting position. When an internal tension is built up, they can and do move, and contraction occurs.
The actin polymer (which is double stranded) is considered to have structural polarity due to the fact that all the microfilament's subunits point towards the same end (ref wikipedia). Therefore you have one "+" and one "-" end of the polymer. The same end of the polymer (say "-") is strongly linked to the Z disk ref, so the system is mirror-symmetric around the M-line, where all the "+" ends arrive, from both sides. Myosin is a molecular motor that walks/pulls directionally on its track, the actin fiber, from "+" to "-". So when all the myosins start to "walk" on their respective actin filament towards the "-" end (or equivalently, towards the Z ring attached to it), contraction is the natural consequence. Each Z ring, not being attached to anything outside the sarcomere, moves towards its relative M line, and contraction happens, starting from anywhere, not necessarily from the outermost sarcomeres.
A: Yes, there is a tug of war, which results in tension being developed in the muscle fibre. As it has the ability to contract, increased tension will cause it to do so. Once the muscle contracts, the muscle has no mechanism to provide an outward force, thus a compressed muscle has to rely on the compression of another muscle to relax. (eg, biceps & triceps)
A: I think your two pictures show how the whole system can contract.
Maybe abstract it as a bunch of springs and balls in series.
s = spring
M = myosin (imagine it as a ball localized at the M line)
A = actin (imagine it as a ball localized at Z line)
Your first pic looks to me like
...MsAsMsAsM...
and the springs are all stretched past their equilibrium point (i.e. they all "want" to contract).
Then it seems pretty clear that the whole system will shorten as all the springs contract.
You can write it all out mathematically with F=ma for each mass and see if your intuition in your Edit is correct -- I'm guessing it is.
A: If the zig-zag part of the z-line was a straight line the myosin would be enclosed in an open rectangular form which is able to move wrt to adjacent open rectangular forms. All the myosins would in this case they had to be lying on one line. Just try to imagine.
In that case, the forces exerted by the myosins (the ones on one of the many parallel lines) on the actin at the non-zig-zagged, straight z-line would be equal but opposite, so there would be no net force acting on the z-line.
Obviously, in that case, there is no contraction possible. Evolution is a miracle!
