Using pneumatic pistons and servos to power robots makes them fast and strong, but also bulky and extremely heavy. No one is going to mistake ATLAS for a real human being. To eventually create humanoid-looking robots like the Terminator, we need to mechanically replicate every part of the human anatomy -- starting with the muscles.
Researchers at the Suzumori Endo Robotics Laboratory at the Tokyo Institute of Technology started with an artificial human skeleton that was then covered in bundles of multifilament artificial muscles. Like real human muscles, the multifilament bundles contract and expand when an electrical current is applied, and by controlling different groups of these muscles at different times, the skeleton's arms, legs and head can all be made to move similarly to how a real human can.
The robot's legs actually contain the same number of muscles that a real human being's legs use to walk, but the Suzumori Endo humanoid can't go for a stroll just yet without additional support. The artificial muscles are still considerably slower than the biological versions that inspired them, making self-balance all but impossible at this stage. But eventually the technology will be improved so that Skynet will eventually having no problem infiltrating and wiping out humanity using Terminators.