Futuristic medical device assessing ankle spasticity.

Beyond the Ashworth Scale: Revolutionizing Spasticity Measurement with New Tech?

Mira Elwood in Health & Wellness December 2025 • 4 min read.

"Discover how the Electric Spastic Ankle Measure (E-SAM) could provide more specific and quantitative insights into muscle tone and spasticity following stroke, potentially transforming rehabilitation strategies."

Spasticity, characterized by a velocity-dependent increase in tonic stretch reflexes, is a common and challenging consequence of upper motor neuron injuries such as stroke and spinal cord injury (SCI). While the clinical definition of spasticity is well-established, accurately measuring and understanding its components remains a significant hurdle in rehabilitation. This lack of precise measurement tools impacts our ability to tailor treatments and fully understand the effects of spasticity, which can be both inhibitory and beneficial depending on the context.

Currently, clinical assessments of spasticity rely heavily on manual tools like the Ashworth Scale and the Modified Ashworth Scale (MAS). These scales are favored for their ease of use and widespread availability. However, they suffer from limitations in reliability and the ability to provide quantitative results. This has spurred numerous attempts to develop more precise measurement instruments, but many of these have proven too cumbersome or impractical for routine clinical use.

A recent study introduces a promising new tool, the Electric Spastic Ankle Measure (E-SAM), designed to quantitatively assess and isolate the spastic and viscoelastic components of muscle tone. This portable instrument offers the potential to overcome the limitations of existing methods, providing clinicians and researchers with a more detailed and objective way to evaluate spasticity.

How Does E-SAM Work and What Does It Measure?

Futuristic medical device assessing ankle spasticity.

The Electric Spastic Ankle Measure (E-SAM) is designed to offer a comprehensive assessment of ankle spasticity through a combination of mechanical and sensor technology. The device incorporates an ankle-foot orthosis (AFO) equipped with torque sensors on an upright bar, a goniometer at the ankle joint, and a foot plate that pivots on an anterior hinge. This setup allows for precise measurement of the forces and angles involved in ankle movement.

Here’s a breakdown of the E-SAM measurement process:

Initial Setup: The patient is seated with the hip and knee joints positioned at 90 degrees, and the ankle is fixed at 10 degrees of plantarflexion using the E-SAM device.
Measurement Initiation: The process begins when a lock bar is released without warning, allowing the foot to drop naturally.
Data Acquisition: As the foot drops, torque and angle data are continuously recorded at a high sampling frequency (1 kHz) using specialized software (LabVIEW).
Automated Locking: Upon reaching 5 degrees of dorsiflexion, the footplate automatically locks into place, stabilizing the ankle.
Data Analysis: The recorded torque and angle data are then analyzed to evaluate muscle tone and spasticity, providing quantitative measures of these parameters.

The E-SAM score, a pragmatic scale of spasticity, is generated by applying a numerical formula to quantify spasticity. This score represents the mean torque during the 1000 ms period following the start of the heel drop and the initiation of a dorsiflexion-generated stretch reflex. This method aims to provide a quantifiable measure of spasticity that can be easily communicated and compared across different individuals.

The Future of Spasticity Assessment

The E-SAM device represents a significant step forward in the quantitative assessment of spasticity, offering a more detailed and objective alternative to traditional manual scales. By providing clinicians and researchers with the ability to measure and isolate the viscoelastic and spastic components of muscle tone, the E-SAM has the potential to improve treatment planning, monitor rehabilitation progress, and advance our understanding of the underlying mechanisms of spasticity. While further research is needed to validate its reliability and applicability across a wider range of patients, the E-SAM holds promise as a valuable tool in the management of spasticity and the improvement of patient outcomes.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

What is spasticity, and why is it difficult to measure?

Spasticity is characterized by a velocity-dependent increase in tonic stretch reflexes and is a common result of upper motor neuron injuries such as stroke and spinal cord injury (SCI). Accurately measuring and understanding its components is challenging because clinical assessments often rely on subjective manual tools like the Modified Ashworth Scale (MAS), which have limitations in reliability and provide only qualitative, not quantitative, results. These limitations hinder the ability to tailor treatments effectively and fully understand the effects of spasticity.

How does the Electric Spastic Ankle Measure (E-SAM) work?

The Electric Spastic Ankle Measure (E-SAM) uses an ankle-foot orthosis (AFO) with torque sensors, a goniometer, and a foot plate. The patient is seated with the hip and knee at 90 degrees, and the ankle is fixed at 10 degrees of plantarflexion. The process begins with an unexpected release of a lock bar, allowing the foot to drop. Torque and angle data are recorded at a high frequency (1 kHz). When the foot reaches 5 degrees of dorsiflexion, the footplate locks. This data is then analyzed to assess muscle tone and spasticity, providing quantitative measurements. An E-SAM score is generated based on the mean torque during the 1000 ms period following the start of the heel drop, which provides a quantifiable measure of spasticity.

What are the key advantages of using the Electric Spastic Ankle Measure (E-SAM) over the Modified Ashworth Scale (MAS)?

The Electric Spastic Ankle Measure (E-SAM) offers several key advantages over the Modified Ashworth Scale (MAS). The MAS is a manual scale known for its ease of use but suffers from limitations in reliability and the inability to provide quantitative results. E-SAM, on the other hand, is designed to offer a more detailed, objective, and quantitative assessment of ankle plantar flexor spasticity. It allows for the measurement and isolation of the spastic and viscoelastic components of muscle tone, providing clinicians and researchers with a more precise way to evaluate spasticity. This leads to better treatment planning and a more nuanced understanding of the condition compared to the subjective nature of the MAS.

How is the E-SAM score calculated, and what does it represent?

The E-SAM score is generated by applying a numerical formula to quantify spasticity. This score specifically represents the mean torque during the 1000 ms period following the start of the heel drop and the initiation of a dorsiflexion-generated stretch reflex. This method aims to provide a quantifiable measure of spasticity that can be easily communicated and compared across different individuals. The score offers a more objective and detailed assessment of spasticity compared to traditional methods like the Modified Ashworth Scale (MAS).

What is the potential impact of the Electric Spastic Ankle Measure (E-SAM) on the treatment of spasticity?

The Electric Spastic Ankle Measure (E-SAM) has the potential to significantly impact the treatment of spasticity by improving treatment planning and monitoring rehabilitation progress. By providing a more detailed and objective assessment, clinicians can tailor interventions more effectively. The E-SAM can measure and isolate the viscoelastic and spastic components of muscle tone. The objective data from E-SAM can help researchers and clinicians better understand the underlying mechanisms of spasticity. While further research is needed, the E-SAM offers the potential to improve patient outcomes and advance the overall management of spasticity compared to reliance on the Modified Ashworth Scale (MAS).