E-SAM device measuring ankle spasticity

Beyond the Ashworth Scale: A New Tool for Measuring Spasticity After Stroke

Samir D’Costa in Health & Wellness December 2025 • 4 min read.

"Discover how the Electric Spastic Ankle Measure (E-SAM) offers a more precise way to assess muscle tone and spasticity in stroke patients, potentially revolutionizing rehabilitation strategies."

Spasticity, characterized by a velocity-dependent increase in tonic stretch reflexes, is a common challenge following upper motor neuron injuries such as stroke and spinal cord injury (SCI). While the condition is well-recognized, accurately measuring spasticity and understanding its components has remained elusive. This is crucial because spasticity can either hinder or help recovery, depending on the context.

Current clinical assessments rely heavily on manual tools like the Ashworth Scale and the Modified Ashworth Scale (MAS). These scales are widely used due to their simplicity, but they have significant limitations in reliability and the ability to provide quantifiable results. The need for more precise and reliable measurement tools has driven the development of instruments designed to quantify spasticity, though many are cumbersome and impractical for clinical settings.

This article explores the Electric Spastic Ankle Measure (E-SAM), a newly developed, portable instrument designed to quantitatively assess the spastic and viscoelastic components of muscle tone. By comparing E-SAM measurements with those obtained via the MAS, researchers aim to demonstrate E-SAM's potential as a more specific and quantitative tool for evaluating spasticity in stroke patients.

How Does E-SAM Work?

The Electric Spastic Ankle Measure (E-SAM) is designed for ease of use and precise measurement. It incorporates an ankle-foot orthosis (AFO) equipped with torque sensors on an upright bar and a goniometer at the ankle joint. A footplate, pivoting on an anterior hinge, completes the setup.

The process begins with the subject seated, their ankle positioned at 10° of plantarflexion. When the heel lock is released, the foot naturally drops, influenced by gravity, to 5° of dorsiflexion. At this point, the footplate is automatically locked. Throughout this movement, torque and angle data are captured at a high sampling frequency of 1 kHz using LabVIEW software.

Viscoelasticity: The initial drop and resistance encountered reflect the viscoelastic properties of the muscle.
Reactive Contractions: Subsequent peaks indicate reactive contractions of the plantar flexor muscles, revealing spasticity.
Data Processing: The recorded data is then analyzed to quantify muscle tone and spasticity, providing a detailed assessment.

To quantify spasticity, researchers developed the E-SAM Score, which calculates the mean torque during the 1000 ms following the start of the heel drop. This score provides a numerical value representing the degree of spasticity, making it easier to compare results across different subjects and conditions.

The Future of Spasticity Assessment

The E-SAM device offers a promising step forward in the quantitative assessment of spasticity, potentially enhancing treatment strategies and improving outcomes for stroke patients. While further research is needed to validate these initial findings across a broader population, the E-SAM shows significant potential as a practical tool for both clinical and research applications.

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Everything You Need To Know

What is the Electric Spastic Ankle Measure (E-SAM)?

The Electric Spastic Ankle Measure, or E-SAM, is a new device designed to measure spasticity in a quantitative way, particularly in patients who have experienced a stroke. It uses an ankle-foot orthosis with torque sensors and a goniometer to measure the resistance and movements of the ankle joint when the foot is allowed to drop. This allows for a detailed assessment of muscle tone and spasticity, helping to improve treatment strategies and outcomes.

What is spasticity and why is it important to measure it accurately?

Spasticity is a condition characterized by an increase in tonic stretch reflexes, leading to muscle stiffness and involuntary muscle contractions. It is a common challenge following injuries to the upper motor neurons, such as stroke and spinal cord injury. Understanding and accurately measuring spasticity is important because it can either hinder or help recovery, depending on the context, and proper management can significantly improve a patient's quality of life.

How does the Modified Ashworth Scale (MAS) differ from the Electric Spastic Ankle Measure (E-SAM)?

The Modified Ashworth Scale, or MAS, is a manual assessment tool commonly used to measure spasticity. While it is simple to use, it has limitations in reliability and the ability to provide quantifiable results. Unlike the Electric Spastic Ankle Measure, or E-SAM, which provides numerical data and detailed measurements of muscle tone and spasticity, the Modified Ashworth Scale relies on subjective scoring, which can vary between different examiners and lack the precision needed for detailed analysis.

Can you explain how the Electric Spastic Ankle Measure (E-SAM) actually works to measure spasticity?

The Electric Spastic Ankle Measure, or E-SAM, works by using an ankle-foot orthosis equipped with torque sensors and a goniometer. The patient's ankle is placed in a specific position, and the foot is allowed to drop. During this movement, the E-SAM captures data on torque and angle changes. This data is then analyzed to quantify viscoelasticity, which is the initial resistance encountered, and reactive contractions of the plantar flexor muscles, which indicate spasticity. The E-SAM Score is calculated from this data to provide a numerical value representing the degree of spasticity.

What is the E-SAM Score, and why is it significant in measuring spasticity?

The E-SAM Score is a numerical value calculated from the data collected by the Electric Spastic Ankle Measure, or E-SAM. It represents the mean torque during the 1000 ms following the start of the heel drop in the device. This score helps to quantify the degree of spasticity, making it easier to compare results across different subjects and conditions. The E-SAM Score is significant because it offers a more objective and quantitative way to assess spasticity compared to traditional methods, like the Modified Ashworth Scale.