This is the third installment of my answer to Mindy's question: Why do kids bunny hop?
1 Variability, learning to balance in prone kneeling and early crawling
2 What abilities are needed for reciprocal crawling
3 Infants who bunny hop need to acquire more variable patterns of movement
In my previous post What abilities are needed for reciprocal crawling? I argued the ability to crawl with a reciprocal arm and leg pattern requires:
1 The ability to balance on one hand and the opposite knee, while at the same time flexing the opposite arm and leg forwards.
2 Upper limb strength is also needed as the weight of the body is shifted forwards over the arm at the end of the stance phase of crawling.
3 The ability to balance on one leg which involves lateral weight shift of the pelvis over the weight bearing leg during the stance phase, and requires adduction to at least 00.
I also argued that infants acquired the ability to balance in prone kneeling through repeated practice and exploring the different options for balancing while moving one arm or leg, and sometimes two limbs at the same time.
What patterns of movement are seen in infants who "bunny hop".
Generally speaking, when an infant uses a bilateral, more or less symmetrical, crawling pattern, they first move the hands forwards, shift the weight forwards onto the hands, then flex the hips and knees and move the knees forwards, using a variety of strategies.
Youtube video clip of infant using bilateral hip flexion pattern
In this clip you see an infant moving the hands forwards one at a time, then extend the right hip and knee, push down on the plantar aspect of the right foot which takes the weight off the left knee allowing the infant to flex the left hip and move the knee forwards, followed by flexing the right hip and knee.
My approach to assessment of an infant who "bunny hops"
Infants who adopt an atypical pattern for crawling will usually have some restrictions in ROM of the lumbar and hip structures, possibly generalized joint hypermobility.
They usually display less variability of postural and movement patterns in the developmental tasks that infant who are sitting independently and crawling should master.
Here I provide a brief review of the sitting and crawling developmental tasks I would assess in an infant who shows an atypical crawling pattern and touch on the impact of restricted hip ROM on motor performance.
Observation of sitting
Posture of the lower extremities.
An asymmetrical sitting posture usually reflects restricted ROM in the lower quadrant.
Wide abduction and lateral rotation of the hips is associated with limited hip adduction in flexion.
Reaching to the left and right and across the body
Shifting from sitting to half kneeling with weight on the arms
Transition from sitting to prone kneeling
See the TOMT 0-3 Online Training Guides for more detailed analysis of active sitting.
Observation of prone kneeling
Posture in prone kneeling: symmetrical or asymmetrical
Weight distribution in A-P direction - position of the COM.
Is the weight shifted back over the LEs?
Position of the hips:
Are the knees aligned below the hips? Widely abducted hips usually indicates restricted hip adduction in flexion.
Balance and weight shift when lifting one hand to reach for a toy
Is the infant able to shift the weight forwards over one arm to reach forwards? Or does he shift the weight back over the LE's to for added stability and to avoid increasing the weight carried by the WB UE?
Observation of crawling
Pattern of movement
Does the child use a reciprocal pattern or some variation of bilateral hip flexion pattern?
Ability to crawl up a step, over cushions, up a slope
Can the child adapt the crawling pattern to accommodate the altered support surface?
Observation of transition to kneeling and standing
Transition from prone kneeling to kneeling at a step.
Can the infant move from prone kneeling to kneeling at a low step?
Can the infant pull up into standing from prone kneeling. Is he able to move through half kneeling?
Assessment of ROM
Presence of joint hypermobility
Infants with generalized joint hypermobility often have restricted adduction of the hips.
Symmetry in supine
Is the pelvis level or tilted up on one side indicating some restricted lumbar movement?
ROM of the hips
In particular restriction of hip adduction in flexion.with 00 of rotation
This movement is often restricted in infant with GJH and infant born preterm.
Decreased range of medial rotation of the knees in flexion is often associated with restricted hip adduction. It is also commonly seen in infants who sit in w-sitting.
Having identified the developmental tasks that the infant has not fully mastered and acquired some insight into the underlying reasons for poor performance on these task, my next step is to create learning opportunities that encourage the infant to explore different ways to achieve the desired outcome.
From a constraints led perspective, task performance is always influenced by the interaction between the infant, the task and the environment.
By adapting the environment, in this case the configuration of the support surfaces, I can decrease the strength and balance requirements of a task, which will often encourage the infant to explore different ways of moving.
Letting the infant kneel facing a step changes the amount of weight carried by the UEs when the weight is shifted forwards.
Encouraging the infant to reach for toys in different directions encourages her to explore different ways to redistribute weight over the contralateral UE and the LEs.
I would also encourage the infant to move from sitting or prone kneeling to kneeling at the step. These maneuvers require complex coordination between the trunk and limbs along with shifts in weight distribution.
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