Stop Muscle Atrophy Before It Starts with Proactive FES
Muscle atrophy, the wasting away of muscle tissue, is a significant and often debilitating consequence of nerve damage or spinal cord injury. A proactive approach using forms of Functional Electrical Stimulation (FES) offers a powerful alternative: stopping muscle atrophy before it even begins and preserving tissue health for the long term.
When a spinal cord injury causes lower limb paralysis, for example, the leg muscles can no longer be exercised and strengthened through conventional methods, affecting muscle mass, circulation, and more. In many of these cases, approaches such as FES Cycling might help, and we'll mention this in more detail below.
If the injury affects the "lower motor neurons," this loss of muscle mass can be particularly profound. In this case the nature of the damage to the nervous system results in "denervation" which means that over time, muscle is gradually replaced by fibrous tissue, collagen, and fat. In these cases, a more specialised form of FES can be used to restore muscle bulk and tissue quality.
For clinicians and patients alike, the rapid decline in muscle mass presents a formidable challenge, impacting mobility, overall health, and quality of life. Traditional rehabilitation often focused on managing the effects of atrophy after it has occurred. Or on suggesting, that nothing can be done.
In this article we touch on the application, and benefits of early FES intervention. We will examine how this approach can preserve muscle integrity, enhance cardiovascular health, and pave the way for better long-term outcomes in neurological rehabilitation. For physical therapists, rehabilitation specialists, and individuals living with nerve damage, understanding the potential of proactive FES is the first step towards transforming recovery.
Understanding Muscle Atrophy
To appreciate the solution, we must first grasp the problem. Muscle atrophy is the decrease in the mass of the muscle. First lets consider what happens in those cases when a muscle loses its nerve supply—a condition known as denervation—it is, in effect, disconnected from the central nervous system. This disruption severs the signalling pathways essential for muscle contraction and tissue maintenance.
Causes and Effects of Denervation
Muscle denervation can stem from various conditions, including:
Peripheral nerve injury
Spinal cord injury (particularly at the T12 level or below)
Neuromuscular disorders like Amyotrophic Lateral Sclerosis (ALS)
Poliomyelitis and Guillain-Barré syndrome
Diabetic peripheral neuropathy
Without the regular electrical signals from nerves, muscle fibres begin to deteriorate. The result is a rapid loss of muscle mass and strength, leading to weakness and impaired function. If left unaddressed, the muscle tissue is eventually replaced by non-contractile fat and collagen. At this stage, the potential for muscle contraction is permanently lost. This underscores the critical importance of early and effective intervention.
The Science Behind FES Therapy
All forms of FES work by using controlled electrical impulses to create an effect. The basic idea is that we are applying energy in a controlled way to the muscle tissue. That energy produces a physiological effect which we hope will be beneficial for some therapeutic purpose.
Most forms of FES for muscle strengthening that you will encounter, rely on the nerve structure within the muscle being intact (an innervated muscle). We describe this in a bit more detail below.
When a muscle is denervated, we use different stimulation parameters to bypass the damaged nervous system to directly stimulate the muscle fibres, mimicking the body's natural mechanism for muscle activation.
How Electrical Stimulation Prevents Atrophy
By artificially inducing contractions, FES helps to maintain muscle mass and prevent the cascade of deterioration that follows denervation. The benefits are multifaceted:
Maintains Muscle Mass: Regular contractions help preserve the structural integrity and size of muscle fibres.
Improves Blood Flow: The "pumping" action of the muscles enhances circulation, delivering vital nutrients and removing waste products.
Promotes Neuroplasticity: FES may facilitate the reorganisation of neural pathways, potentially aiding in the restoration of muscle function over time.
NMES vs. Specialised Stimulation for Denervated Muscle
It is crucial to distinguish between standard Neuro-Muscular Electrical Stimulation (NMES) and specialised technologies designed for denervated muscle. NMES units typically work by exciting the nerve structures within the muscle to produce a contraction. When a muscle is denervated, this nerve structure has deteriorated, rendering standard NMES ineffective.
Muscle Stimulation Parameters are different when there is denervation.
To stimulate a denervated muscle, the electrical impulse must directly depolarise the cellular membrane of each muscle fibre. This requires specific stimulation parameters, such as a significantly longer pulse width (impulse duration). Technologies like the stimulators used in the RISE study are engineered specifically for this purpose. The RISE Stimulator, for instance, produces a form of stimulation energy that acts directly on muscle fibres to generate a useful contraction, even in the absence of an intact nerve.
The Critical Benefits of Early FES Intervention
Whether reinnervation is expected or not, initiating FES as soon as possible after an injury is paramount. Starting early capitalises on the muscle's remaining viability before changes occur. Although we know that muscle and nerve tissue can be rescued much later than once thought, it is always advantageous to start early.
Early intervention offers a host of advantages:
Preservation of Muscle Strength and Bulk: Maintaining muscle tissue from the outset prevents the profound weakness associated with atrophy.
Enhanced Circulation: Improved blood flow reduces the risk of secondary complications like deep vein thrombosis (DVT) and pressure sores.
Improved Cardiovascular Fitness: As we will explore, FES can significantly benefit heart health.
Greater Potential for Neuroplasticity: Stimulating muscles early may keep neural pathways more receptive to potential future recovery.
FES Cycling for Enhanced Cardiovascular Fitness
For individuals with spinal cord injury, maintaining cardiovascular fitness is a major challenge. The inability to perform vigorous, voluntary exercise leads to deconditioning and an increased risk of cardiovascular and metabolic disease. FES Cycling provides an elegant solution when the lower motor neurons are intact. (ie no denervation)
The Stim2go can enable FES cycling with any passive-active bike. Its movement sensors trigger stimulation in the leg muscles at the correct time.
By applying electrical stimulation to the leg muscles in a coordinated sequence that is Synchronised with the movement of the pedals, FES Cycling enables individuals to perform active exercise despite the paralysis or weakness. This activity increases heart rate and oxygen consumption, mimicking the physiological effects of conventional cycling.
Research consistently supports the benefits of FES Cycling for individuals with SCI. Studies have demonstrated significant improvements in:
Cardiovascular endurance
Muscle cross-sectional area
Blood circulation
Overall heart health
A personalised, multidisciplinary approach is key. Aerobic exercise tuned to an individual's specific needs promotes positive vascular adaptations and facilitates better recovery. FES Cycling, as part of a comprehensive rehabilitation plan, can be a cornerstone of long-term health maintenance.
Clinical Guidelines and Protocols
Effective FES therapy for denervated muscle is not a one-size-fits-all approach. It requires specific, evidence-based protocols. The goal is to use a stimulation pattern that mirrors the activity of a normal motor neuron as closely as possible.
Protocols developed from research, such as the RISE study, provided a roadmap for restoring muscle excitability. This often involves a two-stage process:
Initial Restoration (Twitch Contractions): Therapy begins with very long impulse durations (e.g., 120-150 ms) to elicit a "twitch" contraction. This helps to reawaken the muscle's contractile potential.
Building Bulk (Tetanic Contractions): As the muscle responds and training progresses, the impulse duration is gradually reduced. This encourages stronger, sustained "tetanic" contractions, which are essential for building muscle bulk and quality.
A typical initial regimen might involve applying stimulation for 30 minutes in sets of 3-5 minutes each, with rest periods in between, at least five days per week. The stimulation parameters must be individually customised and adjusted over time to ensure optimal results.
Practical Applications of FES Therapy
Technological advancements have made FES therapy more accessible than ever. Portable devices allow patients to integrate treatment into their daily lives, managing their therapy independently at home.
The Stim2Go, for example, is a versatile electrical stimulation solution designed for neurological rehabilitation. It can function as the core of an FES cycling system, compatible with any passive-active bike, and is controlled via a smartphone app. This empowers users to continue their therapy consistently outside of the clinical setting.
The Kt Motion, a handheld stimulation device.
A particularly innovative feature of the Stim2Go is its incorporation of transcutaneous spinal cord stimulation (tSCS) protocols. tSCS is a non-invasive method that applies electrical stimulation through electrodes placed on the skin over the spine. Ongoing research is exploring its benefits for motor function, neuroplasticity, and the management of neuropathic pain and severe spasms. Integrating tSCS with FES Cycling represents a promising, multi-faceted approach to rehabilitation.
Another versatile device is the KT-Motion and its companion products. The KT-Motion provides a wide range of useful functions Including the ability to work with denervated muscles, particularly in the upper limb, and EMG triggering. With incomplete spinal cord injuries, EMG triggering can be used to "listen" for the presence of an intended contraction and use this to trigger the delivery of FES.
Evidence from Case Studies and Research
The effectiveness of proactive FES therapy is not just theoretical; it is backed by a growing body of research.
Almost twenty years ago, We started to offer FES cycling systems with the knowledge that extensive research had established the benefits for many neurological conditions. The main barrier to adoption has not been efficacy, but unfortunately, the relative cost of these systems places them beyond the means of many who could benefit from them.
Previously, severe muscle atrophy caused by denervation was considered untreatable. However, the pivotal RISE study demonstrated that even long-term denervated muscle can be restored. After eight months, participants exhibited significant improvements in muscle mass and function.
Case studies consistently reinforce these findings.
At Anatomical Concepts, we have many clients now using the RISE Stimulator at home. We have more than 20 years of experience working with FES cycling systems with users in both home and hospital environments.
Patients who begin FES cycling or home-based stimulation protocols early after injury are better able to maintain muscle tone, prevent secondary health complications, and report a higher quality of life. These clinical successes provide compelling proof of the power of a proactive approach.
Limitations and Future Directions
Despite its significant benefits, FES therapy is not without its challenges. Ensuring consistent and effective muscle contractions, particularly in severely denervated muscles, can be difficult. The technology requires commitment from both the clinician and the patient, and results can therefore vary.
However, the field is continuously evolving. Ongoing research is focused on refining stimulation protocols, developing more sophisticated devices, and exploring new applications. The integration of technologies like tSCS with FES is just one example of the innovative directions being pursued. Future advancements may lead to even more effective and personalised therapies for preventing muscle atrophy and restoring function.
Expand Your Knowledge with Our Resources
The journey to mastering FES therapy is ongoing. To support clinicians and patients, we offer a range of educational resources.
For deeper exploration, we encourage you to browse our library of articles and product pages:
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A Proactive Stance on Muscle Health
The evidence is clear: a proactive approach to muscle atrophy using FES therapy can fundamentally change the trajectory of recovery after a neurological injury. By intervening early, clinicians can preserve muscle tissue, prevent debilitating secondary complications, and provide patients with a foundation for better long-term health and function.
FES is more than just a treatment; it is a preventative strategy that empowers patients and enhances the toolkit of rehabilitation professionals. We encourage you to explore the options available and consider how proactive FES therapy can be integrated into your own practice or recovery journey. The time to act is now—before the muscle has a chance to waste away.