How to Relax the Anal Sphincter: Methods & Treatments

Relaxing the anal sphincter depends on what is causing it to be overly tight, but proven approaches range from warm sitz baths and posture adjustments you can try at home to prescription topical medications, biofeedback retraining, pelvic floor physical therapy, and, when necessary, minor surgery. The sphincter area actually involves two distinct muscles with different control mechanisms, so the right method varies depending on which muscle is involved and whether the underlying problem is a fissure, a coordination disorder, or chronic pelvic floor tension.

Why the Sphincter Gets Too Tight in the First Place

The anal canal’s resting pressure comes from a combination of structures: the internal anal sphincter, the external anal sphincter, and the puborectalis muscle that loops around the upper canal like a sling. The internal sphincter is a smooth muscle that stays contracted involuntarily, while the external sphincter is skeletal muscle you can consciously squeeze and release.¹ Most problems with an overly tight sphincter trace back to the internal sphincter, because it is the one responsible for continuous resting tone.

Chronic anal fissures are the most common condition linked to excessive sphincter tightness. Research has consistently shown that people with chronic fissures have elevated resting anal pressures that likely represent a genuine increase in the internal sphincter’s baseline tone rather than temporary spasm.² That excess tightness reduces blood flow to the anal lining, which is thought to be the reason fissures hurt so much and resist healing.³ The internal sphincter in these patients relaxes less frequently than it does in people without fissures, creating a vicious cycle of high pressure, poor circulation, pain, and failed healing.⁴

A different but equally frustrating problem is dyssynergic defecation, sometimes called anismus. Instead of the pelvic floor muscles relaxing when you bear down on the toilet, they paradoxically contract or simply fail to let go. This coordination mismatch is one of the most common forms of functional constipation in both adults and children.⁵ The result is incomplete evacuation, straining, and the sensation that something is physically blocking stool from exiting even when no structural blockage exists.

Warm Water and Sitz Baths

One of the simplest and most accessible ways to relax the internal sphincter is applying wet heat. Sitting in a warm bath or a sitz bath (a shallow basin that fits over your toilet seat) has measurable effects on anal canal pressure. In controlled studies, immersing the area at about 40°C (104°F) significantly reduced resting anal pressure in all subjects tested, while cold and room-temperature water did not produce any change.⁶ The pressure-lowering effect is not just brief: in some individuals it lasted up to 30 minutes after a single session.

Research on local thermal stimulation has confirmed that the relaxation response begins roughly three minutes after the skin temperature reaches about 42°C, and it works specifically on the internal sphincter’s tone and oscillation patterns.⁷ This is why sitz baths are routinely recommended after anorectal surgery and for people dealing with fissure pain. The water needs to be warm, not just lukewarm, and the soak needs at least a few minutes to take effect. Cold packs, by contrast, do not relax the sphincter and may make tightness worse.

Toilet Posture

How you sit on the toilet changes the angle of the anorectal canal and how much your pelvic floor muscles need to work during a bowel movement. Squatting widens the anorectal angle and leads to better puborectalis muscle relaxation, which translates into less straining and more complete evacuation compared to a standard seated position.⁸ A broader review of the evidence confirms that squatting may reduce digestive strain and enhance bowel evacuation, though standard sitting toilets offer comfort advantages for older adults and people with mobility limitations.⁹

You do not need to install a squat toilet to get some of this benefit. Placing a small footstool under your feet while sitting on a standard toilet elevates the knees above the hips and approximates a squatting angle. This position helps the puborectalis relax, reducing the grip it has around the upper anal canal. For people whose sphincter tightness worsens with straining, this simple change can make a real difference by lowering how much force is needed to evacuate.

Biofeedback Therapy

Biofeedback is the most rigorously tested non-surgical, non-drug treatment for sphincter-related pelvic floor problems. It uses sensors placed in or near the anal canal to give you real-time visual or auditory feedback about your muscle activity, so you can learn to coordinate relaxation during bearing down. For dyssynergic defecation, randomized controlled trials have shown response rates of roughly 70 to 80 percent, which is unusually high for a behavioral therapy targeting a chronic condition.¹⁰ Based on this evidence, biofeedback is recommended as a first-line treatment for constipation caused by dyssynergic defecation.¹¹

In one early study of women with severe constipation and anismus, biofeedback relaxation training more than doubled weekly stool frequency and significantly reduced abdominal pain and bloating, with improvements sustained for two to four-and-a-half years after treatment ended.¹² The therapy typically involves several sessions with a trained therapist and includes both the sensor-guided relaxation practice and simulated defecation exercises. The goal is to retrain the brain-muscle communication so that the pelvic floor relaxes automatically during a bowel movement instead of clenching.

Breathing Techniques and Their Limits

You may have heard that diaphragmatic breathing can relax pelvic floor muscles, including the anal sphincter. There is a physiological connection: the pelvic floor descends slightly during a deep inhale and rises during exhale, so the muscles are not completely independent of breathing patterns. Research on coordinated retraining of the diaphragm and pelvic floor suggests it can improve quality of life for some pelvic floor conditions.¹³

However, a systematic review of the evidence found that pelvic floor activation during breathing is significantly less than during an intentional contraction, and that adding breathing exercises to standard pelvic floor muscle training did not provide additional benefit for pelvic floor outcomes.¹⁴ Breathing techniques are a reasonable supplement, especially for people who tend to hold their breath and brace during bowel movements, but they are not a substitute for targeted biofeedback or manual therapy when true sphincter dysfunction is present.

Pelvic Floor Physical Therapy

Specialized pelvic floor physical therapy takes a hands-on approach to excessive sphincter and pelvic floor tension. A trained therapist performs internal techniques like stretching the puborectalis muscle and releasing myofascial trigger points within the pelvic floor to reduce muscle tightness and improve circulation.¹⁵ These techniques are tailored to each person based on what a physical examination of the pelvic floor reveals, so the approach is individualized rather than one-size-fits-all.

A related technique called postisometric relaxation involves gently contracting a tight muscle against resistance and then allowing it to lengthen during the relaxation phase that follows. In a controlled trial comparing this method to standard pelvic floor relaxation exercises in women with dyssynergic defecation, both groups improved in defecation time, pain during and after bowel movements, and pelvic floor relaxation. The postisometric relaxation group showed greater improvement across all of these measures.¹⁶ This kind of physical therapy is especially relevant for people whose tightness extends beyond the sphincter itself into the broader pelvic floor musculature.

Topical Medications That Lower Sphincter Pressure

When behavioral and physical methods are not enough, several prescription topical treatments can chemically relax the internal anal sphincter. These are primarily used for chronic anal fissures but work on the same sphincter-relaxation principle.

Nitroglycerin ointment (typically at a concentration of 0.2 to 0.5 percent) donates nitric oxide directly to the sphincter muscle, which reduces the elevated pressure caused by a hypertonic internal sphincter and improves local blood flow.¹⁷ It is applied to the anal margin a few times daily. The main downside is headache, which is common enough that many people stop using it before the fissure heals.

Calcium channel blockers like diltiazem and nifedipine offer an alternative that tends to cause fewer headaches. These work by blocking calcium from entering the smooth muscle cells of the internal sphincter, which the muscle needs to maintain its contracted state.¹⁸ Topical diltiazem at a 2 percent concentration can reduce maximum resting anal sphincter pressure by about 28 percent, and the effect lasts longer than nitroglycerin.¹⁹ Topical nifedipine has shown a high healing rate for acute fissures and may prevent them from becoming chronic.²⁰

Botulinum toxin injection is another pharmacological option, typically reserved for fissures that have not responded to topical treatment. It is injected directly into the internal anal sphincter during an office visit. Manometric studies confirm that it acts on the internal sphincter, and its effect lasts several months as the toxin gradually wears off.²¹ Because the relaxation is temporary, it gives the fissure a window to heal without permanent changes to the muscle. Some people need a second injection if the first does not produce enough healing.

When Surgery Becomes the Answer

For chronic fissures that fail to respond to topical treatments and botulinum toxin, lateral internal sphincterotomy is the standard surgical option. The surgeon makes a small cut through part of the internal sphincter muscle, permanently reducing its resting tone. In one series, 93 percent of patients were pain-free within a week of the procedure.²² The goal is to lower the resting pressure enough to restore blood flow to the anal lining and allow healing.²³

The trade-off with sphincterotomy is a small risk of long-term changes in continence, since the cut to the muscle is permanent. This concern has driven interest in balloon dilation as a less irreversible alternative. Modern controlled balloon dilation uses a measured, standardized approach that is less traumatic than old-fashioned manual stretching. Studies show that pneumatic balloon dilation lowers resting anal pressure effectively and produces high fissure-healing rates with less postoperative incontinence compared to sphincterotomy.²⁴ Controlled manual anal dilation has also shown sustained benefit, with mean resting pressure dropping significantly at three months after the procedure.²⁵

How Doctors Measure Sphincter Tightness

If you are working with a specialist, they may use anorectal manometry to objectively measure your sphincter pressure and coordination. High-resolution anorectal manometry is a newer tool that maps pressure along the entire anal canal and can assess how well the rectum and anus coordinate during attempted defecation.²⁶ The test involves inserting a thin catheter with pressure sensors and asking you to squeeze, relax, and bear down while the device records muscle activity.

Manometry is useful for distinguishing between different types of sphincter dysfunction. A person with a chronic fissure might show uniformly elevated resting pressure, while someone with dyssynergic defecation might have normal resting pressure but paradoxical contraction during bearing down. The distinction matters because the treatment approaches differ: fissures call for chemical or surgical pressure reduction, while dyssynergia calls for coordination retraining through biofeedback. Without objective measurement, it can be difficult to know which problem you are dealing with, especially since the symptoms of straining and pain can overlap considerably.

Sacral Nerve Stimulation

For complex cases where sphincter function is disrupted in ways that do not respond to the standard approaches, sacral nerve stimulation is an emerging option. This involves electrically stimulating the sacral nerves, which control the sphincter muscles and pelvic floor. Short-term sacral nerve stimulation has been shown to notably decrease episodes of fecal incontinence, likely by influencing both the striated (voluntary) sphincter function and the sacral reflexes that regulate rectal sensitivity and anal motility.²⁷ While this is primarily studied for incontinence rather than excessive tightness, the principle of neuromodulation — adjusting the nerve signals that control sphincter tone — has implications for any condition where the usual neural control has gone awry. It is a more invasive and expensive intervention, reserved for people who have exhausted other options.

Choosing the Right Approach

The methods available for relaxing the anal sphincter form a clear escalation ladder, and where you enter that ladder depends on your specific situation. For general tightness, straining, and mild discomfort, warm sitz baths, postural adjustments on the toilet, and conscious relaxation during bowel movements are reasonable starting points that carry no risk. If you suspect dyssynergic defecation — chronic straining with a feeling of incomplete evacuation despite soft stools — biofeedback therapy and pelvic floor physical therapy have the strongest evidence base and should be pursued before medications or procedures.

For chronic anal fissures with confirmed high resting pressure, the typical clinical path starts with topical calcium channel blockers or nitroglycerin, moves to botulinum toxin injection if those fail, and proceeds to sphincterotomy or controlled dilation only as a last resort. Each step trades simplicity for potency and reversibility for permanence. One thing that holds true across all of these methods: any plan that lowers internal sphincter pressure will also improve blood flow to the anal lining, which is why reducing tightness and healing the tissue are essentially the same goal.