Electrical stimulation (E-Stim) is a common and effective modality used in physical therapy to manage pain and restore muscle function. Often informally abbreviated by patients as “STEM,” E-Stim involves using a device to deliver controlled, mild electrical currents to the body through electrodes placed on the skin. The primary goal is to cause a specific physiological response in targeted nerve or muscle tissue to assist in rehabilitation.
How Electrical Currents Affect the Body
The mechanism underlying all forms of therapeutic electrical stimulation is the depolarization of nerve tissue. Electrical current applied to the skin surface must overcome the natural resistance of the skin and underlying tissues to excite the peripheral nerves. When the current reaches a nerve, it changes the electrical potential across the nerve cell membrane, triggering an action potential or nerve impulse.
Physical therapists precisely adjust the electrical parameters of the current to target different types of nerves based on the treatment goal. Stimulating the larger-diameter sensory nerves results in a non-painful sensation, which is primarily used for pain management. Conversely, using a longer pulse duration and higher intensity targets the motor nerves, which are the nerves connected directly to muscle tissue. When motor nerves are activated, they cause the corresponding muscle fibers to contract involuntarily.
Targeting sensory nerves is theorized to alleviate pain through the Gate Control Theory. This theory suggests that activating non-pain-carrying sensory nerve fibers essentially “closes a gate” in the spinal cord. By creating a rush of non-painful signals, the electrical current interferes with the transmission of pain signals traveling to the brain, effectively masking the discomfort.
Categorizing Therapeutic Electrical Stimulation
Electrical stimulation is categorized based on the specific type of nerve it targets and the resulting therapeutic purpose. The two main categories are Transcutaneous Electrical Nerve Stimulation (TENS) and Neuromuscular Electrical Stimulation (NMES). The application of TENS is focused entirely on pain management by stimulating the sensory nerves near the painful area.
TENS uses lower-intensity electrical pulses to block or override the perception of pain signals at the spinal cord level. It is often prescribed for both acute and chronic conditions, such as lower back pain or arthritis, and is set to a comfortable buzzing or tingling sensation. This modality is non-invasive and can be easily used by patients at home with a portable unit after training from a clinician.
In contrast, Neuromuscular Electrical Stimulation (NMES) is designed to strengthen muscles and prevent atrophy. NMES works by stimulating the motor nerves to elicit a strong, involuntary muscle contraction that mimics a voluntary exercise. This type of stimulation is beneficial for patients who have difficulty activating muscles due to injury, surgery, or neurological conditions.
Other forms of E-Stim, such as Interferential Current (IFC), employ two intersecting medium-frequency currents to create a deeper, more comfortable stimulation pattern. IFC is generally used for pain relief and can sometimes penetrate tissues more deeply than standard TENS. Russian Stimulation is a specific waveform of NMES that uses a burst-modulated alternating current to achieve very strong muscle contractions, making it a popular choice for muscle strengthening and athletic rehabilitation.
Patient Experience and Safety Guidelines
Patients typically experience a distinct sensation when undergoing electrical stimulation, which varies depending on the type of treatment. TENS is characterized by a comfortable, mild tingling, buzzing, or tapping sensation felt on the skin beneath the electrodes. NMES, which is intended to cause muscle contraction, results in a more noticeable muscle twitching or pulling feeling. The intensity of the electrical current is adjusted to a level that is therapeutic but never causes outright pain or discomfort.
A standard session of E-Stim in a physical therapy setting usually lasts between 15 and 30 minutes, depending on the specific modality and the patient’s condition. The treatment is applied under the supervision of a licensed physical therapist who ensures proper electrode placement and parameter settings. This professional oversight is necessary because E-Stim is a medical intervention that carries specific safety precautions, known as contraindications.
Safety guidelines prohibit the use of E-Stim in several situations:
- On patients with implanted electronic devices, such as cardiac pacemakers or defibrillators, due to the risk of electrical interference.
- Over areas of known or suspected deep vein thrombosis (DVT) to prevent a blood clot from dislodging.
- Over the pregnant uterus, an active malignancy, or directly over the carotid sinus in the neck.
- Over broken, damaged, or infected skin areas, as skin integrity is a concern.