Transcutaneous Electrical Nerve Stimulation (TENS) is a non-invasive method that uses a low-voltage electrical current to stimulate nerves through the skin. Commonly associated with pain relief, this battery-operated device is now being explored as an at-home tool for managing chronic constipation. Electrical impulses are delivered via electrode pads placed strategically on the body, influencing nerve pathways that regulate bowel function. This guide provides an overview of where to place the TENS pads and what settings to use to improve colonic motility.
How TENS Affects Bowel Motility
The scientific principle behind using TENS for constipation centers on the nervous system’s control over the digestive tract. The colon and lower bowels are heavily influenced by the parasympathetic nervous system, specifically the sacral nerves (S2 to S4). Electrical stimulation delivered to the skin targets these underlying nerve fibers.
Activating these sacral nerves helps modulate the intrinsic reflexes that govern bowel function. This neural modulation triggers an increase in neurotransmitters that promote movement. The goal is to enhance the natural muscle contractions, known as peristalsis, which propel stool through the colon.
By stimulating the nerves that control the large intestine, TENS aims to reduce the slow transit time often seen in functional constipation. This encourages the smooth muscle walls of the colon to contract more effectively and regularly, accelerating the movement of intestinal contents and leading to more frequent bowel movements.
Specific TENS Pad Placement for Constipation Relief
The placement of TENS pads is the most important factor, determining which nerve pathways are stimulated to influence the colon. Primary approaches involve direct nerve targeting in the lower back (sacral stimulation) or direct muscle stimulation over the abdomen. Some protocols use a combination of front and back placement to maximize the current’s effect.
Sacral Nerve Stimulation
This technique involves placing electrodes directly over the skin covering the sacral nerves, generally aiming for the S2 to S4 nerve roots. The sacrum is the triangular bone at the base of the spine. The most common placement involves locating the sacral dimples on either side of the lower back, which often align with the S2 nerve root area.
Two electrode pads are typically positioned horizontally across the lower back, centered over the sacral bone, with one pad on either side of the spine. Alternatively, a four-pad setup may be used, with two pads placed on the lower abdomen and two over the sacral region. This arrangement creates a crossed electrical field, ensuring the current passes through the pelvic nerves that innervate the lower bowel.
Abdominal/Colonic Placement
This approach focuses on stimulating the abdominal wall muscles and the nerves closer to the colon. This method is favored when the goal is to directly encourage muscle contractions in the large intestine, with pads placed directly over the general path of the colon.
Two electrode pads are usually secured on the lower abdomen, often below the navel and above the pubic bone. They may be placed on the left side to target the descending and sigmoid colon, the final sections of the large intestine. The aim is to generate a mild, visible muscle twitch in the abdominal wall, which indirectly stimulates the gut.
Posterior Tibial Nerve Stimulation (PTNS)
A less direct, but well-studied alternative is transcutaneous Posterior Tibial Nerve Stimulation (PTNS), which involves placing pads near the inner ankle. This method works because the posterior tibial nerve shares common nerve roots (L4 to S3) with the nerves that control pelvic organs and bowel function. Stimulating the tibial nerve sends signals up the leg to the spinal cord, where they modulate the sacral nerves.
For transcutaneous PTNS, a single electrode pad is positioned over the tibial nerve, which runs just behind the medial malleolus (the prominent bone on the inside of the ankle). The second pad is often placed a few inches above it on the inner calf. This indirect approach influences the lower bowel without placing electrodes on the torso.
Suggested TENS Unit Settings and Treatment Frequency
The settings used for constipation relief differ from those employed for pain management, focusing on low-frequency stimulation to promote muscle activity. The frequency (pulse rate) should be set low, usually between 10 to 20 Hertz (Hz). Some protocols suggest an even lower frequency, such as 0.5 to 2 Hz, which enhances gut motility and peristalsis.
The pulse width, which determines the duration of each electrical pulse, is set higher than for pain relief, typically between 200 and 500 microseconds (µs). A longer pulse width is necessary to recruit the motor nerve fibers that cause muscle contraction or to stimulate the deep nerves of the bowel. Select a continuous or normal mode setting, avoiding burst or modulation modes unless advised by a therapist.
Intensity should be adjusted until a strong, comfortable sensation is felt, which may cause a visible muscle twitch in the area of the pads. The sensation must never be painful or sharp. Session duration commonly ranges from 20 to 45 minutes, recommended once or twice daily. Clinical studies often involve daily application for several weeks to months to achieve sustained functional improvements.
Essential Safety Precautions
Before beginning TENS therapy for constipation, consult with a healthcare professional to ensure the treatment is appropriate. TENS units should never be placed over areas of broken, irritated, or numb skin. The electrical current must be kept away from the front of the neck, eyes, head, or directly over the chest.
The use of a TENS unit is unsafe and must be avoided by individuals with an implanted electronic device, such as a cardiac pacemaker or defibrillator, as the current could interfere with the device’s function. Since the safety of TENS during pregnancy has not been established, it should not be used over the abdominal or lumbar region during this time.
People with epilepsy or certain neurological disorders should seek medical guidance before use. If you experience skin irritation, dizziness, or increased discomfort during a session, stop the stimulation immediately. Always ensure the TENS unit is switched off before applying or removing the electrode pads to prevent sudden shocks.