When a patient lifts or repositions a prosthetic arm, their muscles naturally contract slightly to stabilize the limb. These postural contractions generate EMG signals and to a conventional myoelectric system, they can look identical to an intentional command. In the upperlimb prosthetic industry, this is known as unintended activation.

Why unintended activation happens

As the patient lifts or positions the prosthetic arm, the muscles naturally contract slightly to stabilize the limb. This postural muscle activity generates EMG signals that may resemble intentional commands.

Conventional myoelectric systems typically respond to signal amplitude alone if the amplitude of one channel is simply higher than the other, the hand will automatically open or close. Consequently, they cannot reliably distinguish between:

• Intentional muscle activation to control the prosthesis
• Background muscle activity related to arm movement or positioning

Research has shown that changes in limb position can alter EMG signal characteristics, increasing the risk of false triggers in traditional control systems. The result: sudden, accidental release of objects during everyday activities such as reaching or adjusting posture.

In the upper-limb prosthetic industry, sudden accidental release of a held object due to postural muscle signals is called unintended activation – one of the most reported frustrations among prosthetic users in daily life.

Vulcan Motion Tracking

The Vulcan Motion Tracking system, integrated into the Myoband sensor band, combines EMG sensing with inertial motion data (IMU) to create a context-aware control model.

By continuously monitoring arm angle, movement state, and muscle activation thresholds, the system can interpret the patient’s intent more accurately. For example:

Scenario	System Response
Arm is raised + EMG increases slightly	Recognized as postural stabilization → no command triggered
Arm is stable + EMG rises above threshold	Recognized as intentional command → prosthetic hand activates

All sensor inputs are time-synchronized and processed through a signal-fusion engine. This allows the control logic to respond differently depending on motion context, velocity, or inferred muscle fatigue without introducing noticeable delay.

This level of integration remains challenging for many conventional systems, as it requires advanced algorithms, real-time processing capability, and a wearable sensing architecture.

Benefits for patients and clinicians

By combining motion tracking with EMG analysis, the Vulcan system provides several practical advantages for both patients and clinicians.

1. Lower risk of unintended object release

One of the most common frustrations reported by prosthetic users is accidentally dropping or releasing objects during everyday tasks, particularly when reaching overhead, adjusting posture, or shifting arm position.

Because the Vulcan system continuously monitors both muscle activity and arm movement, it can distinguish between a postural contraction and a deliberate command. This significantly reduces the likelihood of false triggers, helping patients handle cups, tools, or fragile items with greater confidence throughout the day.

2. More natural interaction

Conventional systems react to muscle signals in isolation, without considering what the arm is actually doing at that moment.

The Vulcan Motion Tracking system adds spatial context to every signal — meaning the prosthetic hand responds based on what the patient is likely trying to do, not just what their muscles are momentarily producing. The result is a control experience that feels more intuitive and less mentally demanding, especially during complex or multi-step activities.

3. Objective rehabilitation data

The Vulcan app records motion and EMG signal metrics during use, giving clinicians access to real, quantifiable data between appointments.

Instead of relying solely on patient recall or in-clinic observation, therapists can review how the prosthesis is being used in daily life — identifying patterns, tracking progress over time, and making more informed adjustments to training plans or device settings. This supports a more data-driven approach to rehabilitation and outcome measurement.

4. Improved long-term usability

Residual limb volume and muscle condition naturally change over time due to weight fluctuation, activity level, socket fit, or the progression of rehabilitation. Static threshold systems can become less reliable as these changes occur. The Vulcan system uses adaptive thresholds and continuous movement awareness to maintain consistent performance as the patient’s limb evolves, reducing the need for frequent recalibration and supporting more stable, long-term prosthetic use.

Faster setup. Better outcomes.

Vulcan’s motion aware control architecture represents a new generation of AI and data-driven upper-limb solutions — designed for real clinical workflows and real patient lives. Learn more about Vulcan →