Well as someone already cursed with a third arm it would only be a hinderace as the human brain learned its functionality with what we already have and extra would be like having to juggle its use instead of the natural flow provided by our existing cortex "ghost". this can be backed up by the fact that even when amputated the brain sometimes senses the appendage. which also gives credit to the body not being the whole being of a human.

Add a third leg....for better performance.

The australian solution seems more simple and effective : https://cdn-images-1.medium.com/max/2000/1*lu9XekzZcXH68oLvcC3ehQ.jpeg

That's great news. We need are soldiers to be more comfortable when they wage war.

Interesting that they went into an office somewhere and pulled one of the pudgy POGs out from behind a desk to be their next top model showing off the capabilities of the third arm. With a M4 no less... the only thing easier to sling around than a M4 is maybe a nerf gun. This thing's cool for its Space Marines turned real life aspect but it seems a little silly as is. Of course, as part of a larger move towards exoskeletons... it gets a whole lot more interesting.

Having family in harm's way, I am grateful for the efforts to make them more effective and bringing them home in one piece.
I was skeptical until I saw the soldier dive to a prone position. I'm impressed, and I look forward to the improvements as they come.

Deres, you are quite correct about simple and effective, but this US prototype addresses some concerns about snagging and clearance. I suspect some combinations are under consideration- and the final design may look VERY different than either design...

They ripped off Aliens 2. http://78.media.tumblr.com/tumblr_ljypc1q2AN1qa1o5zo1_1280.jpg

And the Aussie thing is a rip off of a competitor to the steadicam. Name escapes me at the moment. Nothing new under the sun.

Yup, they don't have enough to carry...