Let’s face it: Modern robots are sissies at best; we seem to be a long way off from the powerhouses that we enjoy in sci-fi films like I Robot. Most robots can’t even lift half of what they weigh, and robots designed to be stronger than that aren’t mobile enough to move around like humans.

That’s what makes a recent breakthrough a big deal in the field of robotics: For years now, scientists have recognized the value of trying to mimic what they see in nature. Thus, the field of biomimetics was born. Applying these same principles to the field of robotics means trying to make robot muscles more like human muscles. Of course, robot muscles aren’t going to be burning carbs, so there has to be a different power source; so far that has meant things like heat, ions and electrical fields.

The key to muscle strength is extension; the more you can stretch a muscle out, the stronger it is. At present, robotic muscles can stretch about 300%. It not only limits how strong robots are, but also the amount of control they have over the load they carry.

The solution that researchers have developed is a polymer that reacts to electric fields. Using such a method, it is feasible to create artificial muscles that can lift up to 500 times their own weight. While we aren’t there yet, current tests are still showing astounding results.

The polymer reacts almost instantly to stimuli—that means more human-like reactions rather than those jerky, well, “robotic” movements we’re used to. Plus, no human can lift many times their body weight, but that’s what these new artificial muscles could do. According to researchers, we’re about half a decade away from humans no longer being able to defeat robots in arm-wrestling matches.