April 30, 2019
Pondering Postural Control: Anticipatory Mechanisms
We’re all getting goose bumps thinking about all the possibilities here – amiright? It’s true I get super enthusiastic about this piece of the postural control pie and during this discussion I hope you do too.
Consider last month we talked about reactive mechanisms; the literature indicated that children with sensory and motor challenges often have some degree of RPAs which is characterized by direction-specific control. The characteristics of this control differ, and it is not as efficient as that of neurotypical children, but it is present.
When we talk about anticipatory postural adjustments (APAs), it appears there may be different layers to this piece. The literature regarding children has begun to discuss early postural adjustments vs. anticipatory postural adjustments.
The research regarding adults has an entire body of literature (courtesy of Hodges and others) that indicates the deep core team of the respiratory diaphragm, pelvic floor, transversus abdominis and multifidus serves as an anticipatory synergy, generating intra-abdominal pressure as a stabilizing force for the lumbar spine and pelvis. This team activates in the same way before each movement regardless of the direction of that movement. The activation of this team also impacts the function of distal muscles.
When I conceptualize the sequence of events during movement it goes something like this: the deep core muscle team creates stability at the trunk and pelvis in anticipation of movement (= anticipatory central stability). This activation provides a stable base of support (BOS) and the rest of the muscles/body segments work off of this base. The brain anticipates where it the body is going and makes adjustments to manage the centre of mass (COM) in relationship to the BOS (= early postural adjustments). As body begins to move, the brain keeps responding to movement with reactive adjustments to maintain the COM within the BOS. But almost simultaneously the brain forecasts where the body will need to be given the new position and further anticipatory adjustments occur. This interplay between anticipatory and reactive adjustments occurs as needed to keep the COM within the BOS throughout the movement. And all of this happens unconsciously – proving that the brain is indeed, awesome.
But what about anticipatory mechanisms in children with sensory and motor challenges? Therapists have been discussing difficulties with core stability in children with motor and sensory challenges for many years. I document altered alignment at the rib cage and pelvis in all of my clients, which impacts the ability of the inner core team to create the intra-abdominal pressure that is crucial to lumbopelvic stability. And while the respiratory diaphragm has a big impact as a primary driver of the team, the dynamic relationship between the diaphragm and pelvic floor is equally as important for higher level gross motor skills such as unilateral stance, gait, running and jumping. I’m fond of saying “you can’t master the monkey bars without the pelvic floor”.
There is no literature that looks specifically at the function of the inner core team in children. However there is literature that examines anticipatory postural control. This information indicates that children with CP utilize co-contraction as the preferred strategy and children with ASD substitute reactive control for missing anticipatory control. No wonder their movement appears uncoordinated.
So it turns out that how the brain/body prepare for movement is incredibly important. Treatment of the anticipatory system is where we can have a huge impact on function. Some points to consider:
- Researchers have recommended intervention to improve anticipatory postural adjustments.
- Alignment matters. However, it’s not just pelvic alignment that is important because all the inner core team members need to be working together.
- One recent study indicates that inspiratory muscle training does indeed improve trunk control in children with CP.
Integral to both anticipatory and reactive mechanisms is the concept of keeping the centre of mass within the base of support. So next month we’ll discuss Stability limits.
Are you interested in learning more about how to assess and treat anticipatory central stability in children with sensory and motor challenges? In honour of PT month, Dynamic Core for Kids is on sale from May 6 – 13, 2019. You can use the discount code PTMONTH25 and get 25% off any of my online courses.