The Non-Elastic First Layer
The Serola Sacroiliac Belt does not use a buckle. It is meant to be applied as tight as one can pull it when overlapping one's hands. The intention is to compress the soft tissues of the hips so that, when the sacroiliac joint opens, it stops at its normal end of range of motion. For this reason, the belt must have a non-elastic component.
However, the other non-elastic sacroiliac belts have buckles that give one enough leverage to easily reduce motion below normal. Makers of this type of SI belt encourage the user to pull it tight and lock up the joint. This concept goes back to the days when the sacroiliac joint was thought to be immobile and any motion was a sign of instability. Research over the past several decades has demonstrated that the SI joint does have a small amount of motion, which is necessary for its proper function.
The problems with wearing a belt that reduces sacroiliac joint motion below normal are significant. Like all tissue, ligaments atrophy with disuse. Immobilization, or artificial support, that reduces motion below normal will lead to re-absorption of collagen, causing thinning and weakening of the ligament both in structure and in its attachment to bone, increasing risk of injury with sudden, increased activity Solomonow . The tension developed by the Serola Sacroiliac Belt allows normal movement within the sacroiliac joint's normal range of motion, preventing insufficient or excess motion from further damaging the ligaments.
Also, reducing motion below normal, in any joint, reduces the normal pumping mechanism that brings in oxygen, and other nutrients, and removes metabolic waste, like lactic acid, etc. These wastes are acidic, which lowers the pH. The body responds by shunting in calcium to neutralize the pH, which can result in arthrosis.
Freeman suggested that crushing pressure to a joint capsule can result in nociceptive input (pain), and trigger muscular spasm directly through the alpha motor neuron. The leverage provided by a buckle makes it easy to over-tighten the belt and may injure the blood and lymph vessels within the interosseous ligament. This is important when considering the effects of applying a sacroiliac belt too tightly, and may be the reason one's muscles weaken when the belt is too tight.
Mens above, used pressures of 50 and 100 Newtons (100 N = 22.48 pounds), as well, and found no significant difference in effects between the two pressures, in either the high or low positions. However, they suggested that higher pressures can be injurious. A buckle can provide much higher pressures.
Vleeming stated "Movement was significantly restricted by application of a non-elastic belt (about 2 inches wide) with a tension of 50 N…A comparable result was obtained with the 100 N belt (100 N = 22.48 lbs). Larger forces did not give better results…and may even be counterproductive because the symphysis is artificially compressed." Average rotation from end range of nutation to end range of counternutation was reduced by 29%, a significant improvement.
Snijders  states "With respect to patients suffering from peripartum pain, the assumption is followed that hypermobility in the SI-joints can cause serious impairments. A method to restore pelvic stability is the use of a pelvic belt. The fact that using such a belt can reduce pain may be the reason why in several cultures (e,g. Indonesia, Turkey, Morocco) an elastic corset is worn about the S-2 level from about the 6th month of pregnancy onwards. According to our biomechanical model we conclude, that if such a belt is put on with a small force resembling the force in laces to close a shoe, this will be sufficient to generate a self-bracing effect in the SI-joints under heavy load. A large belt force is not recommended, because it can cause irritation and oedema and it may be detrimental for the symphysis." Snijders developed a biomechanical model that supports the concept that a sacroiliac belt, placed above the greater trochanters and below the sacroiliac joint is sufficient to create a self-bracing effect on the sacroiliac joint. He suggested that placement just below the sacroiliac joint itself helps prevent nutation of the sacrum by limiting the backward rotation of the sacral apex.
In their book, Richardson et al.  discuss the above relationships and mention possible causes of the delayed response of the transversus abdominis and other abdominal muscles, including central nervous system influences, such as opposing muscle tightness, vestibular dysfunction, trunk muscle dysfunction, and reflex inhibition. All of these influences may be seen in a sacroiliac injury. Reflex inhibition has been linked to effusion, pain, ligament stretch, and capsular compression. The first three occur in the nutation lesion of the sacroiliac joint and the last one occurs when a sacroiliac belt is placed too tightly on an injured sacroiliac joint.
What a sacroiliac belt should do is act like a ligament, which it is meant to support. A ligament does not compress the joint. Instead, it provides a non-elastic stop point at the end of range of motion. The Serola Sacroiliac Belt is the only belt that is designed to act like a ligament. It prevents the SIJ from opening beyond normal.
The non-elastic first layer is meant to compress the soft tissue of the hips, enough to remove any slack, and provide a stop point at the end of range of motion.
The Elastic Second Layer
Elastic-only belts may give compression and allow better joint function in a neutral posture, but they do not provide a stop point at the end of motion. So, when the wearer bends, lifts, or twists, the joint can easily open beyond normal, re-injuring the ligaments and de-stabilizing the joint. In this respect, a belt that depends on elastic compression can provide a false security.
Some manufacturers of elastic belts, or belts with elastic components, say that they can improve sacroiliac stability because they assist the action of various muscles, e.g. the transverse abdominis, multifidus, and those of the pelvic floor. However, there is little question that any belt that replaces muscles can cause weakness and atrophy in the targeted muscles, as is known to happen with lumbar belts. Additionally, the mentioned muscles induce nutation and can further injure the sacroiliac joint if enough compression is furnished; this is why the body inherently inhibits these muscles in the presence of a sacroiliac injury. It does not make sense to support the action of muscles that the body is trying to turn off.
Damen  noted that the leverage provided by a sacroiliac belt is similar to that of the transverse abdominis muscle which, by its attachments on the ilia and, using the posterior pelvic ligaments as levers, can strongly compress the SIJ. This leverage makes high belt tension unnecessary and not recommended. Additionally, because the posterior pelvic ligaments would already be sprained, mimicking the action of this muscle may be harmful. The body inhibits the transverse abdominis for a reason. Using the sprained ligaments as levers can only damage them further. Any belt that pulls the ilia anteriorly in this manner risks greater trauma to the posterior weight bearing ligaments. On the other hand, the Serola Sacroiliac Belt pulls the ilia backward, toward the sacrum, putting direct compression on the sacroiliac joint.
The actions of bending, lifting, or twisting significantly increase the likelihood that the sacrum will go past normal range of motion, re-spraining the ligaments and re-injuring the joint.
- When bending forward, the alignment of the joint surfaces tends to allow the sacrum to fall anteriorly, away from the ilia, furthering the nutation lesion. This likelihood is enhanced when the elasticity of the belt, by mimicking the action of muscles such as the transverse abdominis and multifidus, is pulling the joint into nutation.
- During lifting, the additional axial force will load the sacrum and can push the sacrum downward, past normal nutation into lesion.
- Twisting provides an additional nutation force that is transferred from the spine to the sacrum, forcing the sacrum anteriorly into nutation lesion.
Bending, lifting, and twisting are bad enough. The body innately inhibits muscles such as the transverse abdominis and multifidus because they would further the nutation lesion; it would seem ill-advised to recreate their force with an elastic component. Support to reinforce these muscles is unnecessary and can be counterproductive.
The Serola Difference
The elastic layer enhances force closure by providing compression and resilience, but within the range of motion established by the non-elastic layer. It helps compress the joint and assist the bands of the interosseous ligament to re-integrate into the joint surfaces of the sacrum and ilium. Our focus is to compress and support the joint itself, which allows the muscles to function normally. No further support to the muscles is needed, or recommended. Additionally, the front-to-back pull of the elastic brings the pelvis back toward neutral stance so that one is standing straighter and taller, minimizing stress on the lumbo-sacral vertebrae, discs, facets, and nerve roots.
Together, the two layers normalize the motion and, thereby, the function of the sacroiliac joint. The elastic layer is not meant to reinforce specific muscles. However, overall muscle strength, and function, can be restored to normal, throughout the body, with the Serola Sacroiliac Belt.
It should be noted that the elastic layer is insufficient to push all of the fluid from the joint space, and cause healing of the sacroiliac joint. Another means has been developed to do just that, category 2 pelvic blocking (see the ).
- Solomonow M: Ligaments: a source of work-related musculoskeletal disorders. J Electromyogr Kinesiol 2004, 14:49-60.
- Freeman MA, Wyke B: Articular reflexes at the ankle joint: an electromyographic study of normal and abnormal influences of ankle-joint mechanoreceptors upon reflex activity in the leg muscles. The British journal of surgery 1967, 54:990-1001.
- Mens JM, Damen L, Snijders CJ, Stam HJ: The mechanical effect of a pelvic belt in patients with pregnancy-related pelvic pain. Clinical biomechanics (Bristol, Avon) 2006, 21:122-127.
- Vleeming A: Towards An Integrated Therapy For Peripartum Pelvic Instability-A study Of The Biomechanical Effects Of Pelvic Belts. In Proceedings of the 1st Interdisciplinary World Congress on Low Back Pain and its Relation to the Sacroiliac Joint. 1992
- Snijders CJ: Transfer of Lumbosacral Load to Iliac Bones and Legs: Part 1 - Biomechanics of Self-Bracing of the Sacroiliac Joints and its Significance for Treatment and Exercise. Clinical Biomechanics 1993a, 8:285-294.
- Richardson C, Jull G, Hodges P, Hides J: Therapeutic Exercise for Spinal Segmental Stabilization in Low Back Pain. Churchill Livingstone; 1999.
- Damen L, Spoor CW, Snijders CJ, Stam HJ: Does a pelvic belt influence sacroiliac joint laxity? Clinical biomechanics (Bristol, Avon) 2002, 17:495-498.