Skip to content

Whole Body Extensor Spasms and Dynamic Seating

Whole Body Extensor Spasms and Dynamic Seating

Michelle L. Lange, OTR/L, ATP/SMS

Some individuals with cerebral palsy or related conditions experience “frequent whole body extensor spasms which cause their limbs, neck, and back to extend involuntarily and powerfully. These spasms can cause discomfort and pain” (Adlam, et al., 2009). Some individuals exert enough force to extend at the hips and knees until appearing to ‘stand’ in the wheelchair (Avellis, et al., 2010; Hong, et al., 2006, pg. 4).

In the past, whole body extensor spasms were often referred to as an Extensor Thrust or Extensor Thrust pattern, referring to the extension which could suddenly and forcefully occur at the client’s hips and knees. Whole Body Extensor Spasms is a recently introduced term which is more descriptive of what is actually happening to the body.

Below is an individual with cerebral palsy experiencing a whole body extensor spasm while sitting in a wheelchair with Dynamic Seating.

seating dynamics blog 146 starting position

Figure 1.
Relaxed upright sitting position.

seating dynamics blog 146 extended position

Figure 2.
Whole Body Extensor Spasm leading to hip, knee, and neck extension, Dynamic Seating moving with client in response to client force, storing energy and allowing return to original position once force ceases, without loss of position, in combination with appropriate seating system.

seating dynamics blog 146 starting position

Figure 3.
Return to upright with assistance from Dynamic Seating without loss of position, relative to the seating system.

In a static seating system, as client force is imparted against a non-yielding surface, extensor forces increase. Spasticity increases with resistance, such as client forces exerted against a non-yielding surface (Bar-On, et al., 2018). As this force is not accommodated, the client extends at the hips and knees, moving in relation to the static seating surfaces. This can result in a client who is literally standing up in their wheelchair seating system and experiencing shear forces between the posterior trunk and back of the seating system. When the Whole Body Extensor Spasm subsides, the client ceases hip and knee extension, collapsing back into the seating system. As the seating surfaces are static, there is nothing to guide the client back to the preferred seating position. Typically, the client ends up sitting in a posterior pelvic tilt.

With a Dynamic Back, as client force is imparted against a now yielding surface, extensor forces are diffused, and the support surfaces move with the client’s body surfaces. This contact limits shear forces and, in combination with a correct pivot point, returns the client to the preferred seated position, without loss of posture.

Do you work with clients who experience Whole Body Extensor Spasms? If so, we’d love to hear from you! Just leave a comment below and I will be in touch!


  1. Kirsten Pepper on July 25, 2023 at 1:50 pm

    I have seen children seated in dynamic systems which have acted as a personal gym constantly having a work out during extensor patterns increasing asymmetrical muscle mass. By closing the hip angle has resulted in decreased extension and more comfortable relaxed time in the wheelchair. I am interested in any research with this area.

    • Michelle Lange on July 26, 2023 at 9:54 am

      Kristen, thanks for your comment, this is a very astute question. Closing the hip angle can often inhibit hip extension, however can also make it more difficult for the client to sit upright without falling forward. Many clients, even with the seat to back angle closed, persist in extending at the hips, moving out of alignment with the seating support surfaces, creating shear, and opening their hip angle. We have some other blogs which address this issue and I will also list them in the comments. Thanks so much and always feel free to reach out to problem solve complex client scenarios!

      • Francis on June 20, 2024 at 2:09 pm

        Hi Michelle,

        I work with people that have suffered a stroke and some present with extensor pattern….. we don’t always have the luxury of having dynamic seating available. Possibly, as a result, some clients end up slouched in chair/seated position with tendency to slide out of chair . I wonder whether it is possible to mistaken those presenting with extensor pattern for having weak core/trunk when it may be more to do with extensor activity? Further more, is there any research you could signpost re flexor pattern?

        • Michelle Lange on June 20, 2024 at 7:20 pm

          Francis, thanks for your comment, you bring up some great points.
          First, people who have experienced a stroke can certainly demonstrate anything from flaccidity to rigidity, typically in the extremities. This is not typically a ‘whole body extensor spasm’ which is much more common with velocity dependent tone, such as in common in clients with diagnoses such as cerebral palsy.
          Second, you mention that you do not always have access to dynamic seating. Is this because you work in a long term care facility and there are funding issues?
          Third, this is really a wonderful point. Many people who have strong extension in the extremities actually have low tone and/or weakness at the core – trunk and neck. With that said, it is very possible that someone may observe a client who is in a posterior pelvic tilt and trunk flexion and assume this is only due to trunk hypotonia or weakness and not realize that the client has extended their hips and moved into this position. It is nearly impossible to ‘sit up straight’ with the pelvis in this position. We have a recent blog that addresses this: Please check it out and let me know your thoughts, I believe this addresses your point.
          Fourth, I do not know of research off-hand on a flexor pattern in clients who have had a stroke. This is a documented phenomena and so research may be more focused on prevention or treatment of this issue.
          I truly hope this is helpful and welcome any more questions or thoughts!
          Michelle Lange

  2. Sue on August 3, 2023 at 8:44 am

    Hello I am an OT on Vancouver Island and I am very interested in this system but when I tried to get one on for trial with a local vendor they were told they were not available for trial. Given the high purchase cost, the client could not proceed as restocking charge was too high if it did not work.
    Have you given any though to making this available for trials through medical vendors?

    • Michelle Lange on August 3, 2023 at 12:49 pm

      Sue, this is a common question, so much so that we wrote a Blog on Dynamic Seating Assessment when an equipment trial is not an option. You can find the Blog here:

      I perform seating and mobility evaluations, as well, so I understand. There are many situations where I am unable to trial actual products that are customized to the client, so I must rely on other strategies to simulate those solutions. I hope the blog is helpful.

      Seating Dynamics is working hard at providing our products in Canada. I am presenting on Dynamic Seating next month in Toronto, so if you will be at the Canadian Seating and Mobility Conference, I hope to meet you! Some Seating Dynamics products are available on Canadian manufacturer order forms now, which eases ordering and hopefully funding. Finally, we are putting together a PDG chair now with Dynamic Back, Dynamic Footrests, and Dynamic Head Support Hardware. This chair will actually start its journey in Vancouver before traveling to Toronto for the conference. If you would like, we can try and set-up a time for your to see it. It is unlikely to fit your client’s dimensions, but it is helpful to actually see and try out.

      Thanks, Michelle Lange

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.