Nerves Can Be Fooled into Thinking Prosthetic Limbs Are Lighter than They Really Are
Scientists from ETH Zurich are conducting experiments with nerve manipulation that can reduce the perceived weight of prosthetic limbs.
Prosthetic limbs have come a long way since the days when they were just hunks of wood or plastic. Today’s prostheses can incorporate all kinds of robotic technologies and are often constructed from advanced materials like carbon fiber to keep their weight down. Even so, they can feel quite heavy. That’s particularly true when they contain motors and batteries. Not only can the weight of a prosthesis cause fatigue, it can cause issues with the wearer’s gait. That’s why scientists from ETH Zurich are conducting experiments with nerve manipulation that can reduce the perceived weight of prosthetic limbs.
This nerve manipulation does not actually make the wearer any stronger and it certainly doesn’t reduce the real, physical weight of a prosthetic limb. But by making a prosthesis feel lighter to the wearer, their comfort can be improved. That helps amputees feel more confident and less distracted by their prosthetic limbs, particularly for leg prostheses that play a significant role in a person’s gait. If you’ve ever had to wear heavy boots for a day, you know that even a relatively minor weight difference can dramatically affect the way you walk. That is a far more prominent issue for leg amputees, who can have a prosthetic leg that technically weighs much less than their natural leg, but which feels heavier. This technique can help narrow that divide and make it easier for amputees to walk and run.
To accomplish this seemingly-magical feat, the ETH Zurich scientists stimulated the amputee’s residual leg nerves with electrical impulses. This is an extension of previous work that was intended to provide amputees with sensory information coming from their prostheses, such as the feeling of a prosthetic foot touching the ground. As a byproduct of that research, they found that nerve stimulation could also reduce the perceived weight of the prosthesis. In their testing, they found that amputees perceived their prosthetic legs as being 23% lighter on average. That may not sound like a big number, but it had a real effect. 36% of test subjects reported that that perceived weight reduction was enough to make them feel more confident when walking. An even greater number — more than half of test subjects — reported that their prostheses felt more like natural parts of their bodies. This does require electrode implants, but the team hopes to commercialize the technology in the future.
