How Different Prosthetics Help You Feel

By Marins Med

What is proprioception?

Imagine picking up a paper cup full of water. Now imagine switching to a hammer. You don’t think about how much force to use — you just do it, adjusting automatically. That’s because your body is constantly giving your brain feedback about what you're doing, how much pressure you're applying, and where your limbs are in space.

When someone loses an upper limb, they don’t just lose the physical structure — they also lose the feedback loop that tells them how their body is moving and interacting with the world.

Prosthetic devices aim to restore function, but they don’t all handle feedback the same way. And that can make a big difference in how natural or effective the device feels.

Voluntary Opening (VO) Body-Powered Devices

In VO systems, a cable runs from the prosthetic terminal device (like a hook) to a harness worn by the user. The hook is normally closed, and the user opens it by pulling on the harness.

The grip strength is determined by a spring or rubber bands, not by the user. Once released, the hook snaps shut. While functional, this setup removes the user from direct control over force — making it difficult to apply just the right amount of grip without visual monitoring. This limits feedback and fine-tuned control.

Myoelectric Devices

Myoelectric hands are powered by motors and controlled by muscle signals in the residual limb. They can offer multiple grip patterns and a more natural appearance.

However, feedback is still a challenge. Most users must watchtheir hand during tasks, because they can’t truly feel how much pressure they’re applying. Advanced systems are experimenting with haptic or vibratory feedback, but those technologies are still evolving and can add cost, complexity, and maintenance needs.

Voluntary Closing (VC) Body-Powered Devices

In VC systems, the user actively closes the terminal device using body movement — typically shoulder or arm motion that pulls on a cable. The grip strength increases in proportion to the user’s effort. Letting go releases the grip.

This system allows users to feel how hard they’re gripping, not through the prosthetic itself, but through the muscle tension in their own body. That creates a surprisingly intuitive feedback loop — one that begins to restore the kind of control and confidence most people take for granted.

• Research shows that users of VC devices often report greater confidence in their grip force and increased ability to perform tasks requiring variable pressure (like holding a paper cup vs. a hammer).
• A 2015 JRRD article discusses how voluntary closing mechanisms can improve task performance by creating a more intuitive feedback loop.

The ProHensor: Voluntary Closing & Locking (VC&L)

The ProHensor builds on the principle of voluntary closing and takes it a step further by adding a self-actuated locking system — giving users even more control and versatility.

With the ProHensor, users can:

• Control the grip strength in real time through body movement — just like traditional VC devices.
• Lock the grip at any point, maintaining tension without continuous effort.
• Unlock instantly, making transitions between tasks smoother and less fatiguing.

This Voluntary Closing & Locking (VC&L) system offers a blend of feedback, force control, and function. Users don’t have to choose between strength and subtlety — they can have both.

That means more confidence, more independence, and more freedom to handle the tasks of everyday life — from delicate cooking to heavy lifting — without switching devices or relying on guesswork.

Why It Matters

When prosthetics offer meaningful, intuitive feedback, users engage more fully. They don’t have to think so hard, look so often, or worry so much. They can trust the tool — and get back to living.

 

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Want to Experience the Difference?

Learn more about the ProHensorand how Voluntary Closing & Locking can help you feel more confident, in control, and ready for anything.

👉 Visit www.marinsmed.comto explore the ProHensor, see real-life demos, or get in touch with our team.

Because when it comes to prosthetic function — feedback isn’t just nice to have.
It’s essential.

  

Research Citation

Smit, G., Plettenburg, D. H., & van der Helm, F. C. T.(2015). The lightweight Delft Cylinder Hand, part 2: Biomechanical evaluation of a voluntary closing adaptive hand. Journal of Rehabilitation Research and Development (JRRD), 52(3), 233–246.