#MilestoneMonday / Standing
Gaining verticality is an exciting perspective for your developing baby. Like sitting up, this opens up more possibilities for interaction and discovery. Weight bearing on their feet against gravity is also a major stimulus for babies’ musculoskeletal development. Additionally, standing can be viewed as a precursor to stepping and walking. Independent standing is usually learned near 12 months; however, the work towards standing alone begins with standing with support, which is much earlier. Standing at a supportive surface is typically learned at 6 months.
Before one can learn how to stand independently they must first master their base of support, and how their centre of balance interacts with their movements within this area. To simplify this relatively complex interaction, it is best to minimize the number of degrees of freedom of movement that the baby has to account for when trying to stand. For reference, we can move in three planes; they are the sagittal (front and back), frontal (side to side) and transverse (rotation) planes. This is achieved by the supportive surface. For an early stander, they would be facing squarely to the surface, with both hands firmly placed on the support. This position removes the balance requirements that the baby is required to account for moving forwards and backwards (in the sagittal plane), and rotating left and right (in the transverse plane). This leaves only lateral weight shifting movements to the sides relatively “free” (in the frontal plane). Yet, as we will learn, babies seem to be built to have some inherent stability in the frontal plane to facilitate learning movement in this plane.
When a baby is attempting to stand at a surface, one may notice that the baby’s feet are quite widely spread. Early in the baby’s skeletal development, their alignment through their legs are actually biased to have to be wider to be more stable when weight bearing. In fact, a baby may appear to be “bowlegged” early in their alignment, but this is to be expected, because as they physically mature, this alignment is expected to resolve into a more neutral alignment where their feet are narrower and legs have a straight appearance. However, this immature alignment effectively widens the base of support and lowers the centre of gravity, thus making the child more stable. Thus, this developmental stability allows for slight weight shifting movements left and right that the child can explore when standing at support. As a result, the first component of standing that a baby will learn is mastery of the frontal plane in standing, or, weight shifting left and right in standing. Yet, this makes a lot of sense that they would achieve this first, because weight shifting left and right is a critical component of walking; taking the full weight on one foot is necessary to unweight the other foot for movement. Mastery of weight shifting allows the baby to learn and explore cruising steps left and right, and ultimately culminates in taking steps forward.
Also, when learning how to stand at a support, there is the additional layer of the strength that is needed to support their bodies in a position where they are weight bearing on their feet. This means that their anti-gravity muscles through their legs and trunk must work in synergy to achieve standing. Early on, when standing at support, their arms must also work in unison with the rest of their body to maintain standing. It will be difficult early on to maintain standing, so babies tend to hold on to their support surface with everything they have; they will hold on with their arms, and may lean their trunk against the supportive surface. For some with gross motor delays, this tends to persist well passed 12 months, where they prefer to rest their bodies against a support surface. Although this may be a functional position, this eliminates the use of their trunk and leg muscles to provide them with balance when they are standing. Thus, an important strengthening opportunity is missed.
In the next post, we will discuss activities that can be performed to facilitate standing at support and standing.
By: Chris Dahiroc P.T.