In this post I would like to share with you the insights I have gained watching and re-watching a series of video clips of three infants learning to stand with support. Each infant followed a different  developmental pathway:  

• Will, who followed a typical path and achieved all the AIMS items at the right age. 
• Roan, who was born late pre-term and tended to respond to balance challenges with extension. 
• Max, also born late pre-term who took time to develop effective lower limb extension against gravity. 

My excitement in viewing the video clips of these three infants learning to stand with support, was discovering that all three progressed in the same incremental way, as they made use of  the available physical resources to support their ability to stand with their weight on the LLs and reach for toys in different directions.  

Letting an infant stand facing a  hip or waist high support surface allows them  to independently explore taking weight on the feet, chest and forearms, in positions that increase the A-P dimension of the base of support (BoS) which makes the position more stable. 

With practice and over time the infant starts to experiment with shifting more of the weight onto the feet until they are able to stand with the hips extended and use light touch with one hand to help with balance. 

At this stage of supported standing the infant is able to adapt weight distribution over the feet to maintain balance while reaching in all directions, reaching down to retrieve a toy from the floor, taking steps to the side and squatting with good control to sit down on the floor. 

Postural sway as exploratory behavior 

Perhaps the most exciting new insight into the development of control of the upright position has been the observing the postural sway present during standing with hand support. 

This is particularly interesting in view of Carpenter et al's research that suggests that postural sway may be used by the CNS as an exploratory mechanism to ensure that continuous dynamic sensory inputs are provided 

The presence of postural sway is best illustrated by the following short video clips. 

Will 9 months: postural sway standing with light hand touch 
Will has learned to stand with the trunk erect and the hips in extension, using light touch of the hand on the support surface to aid in balance. In this position the postural sway is clearly seen. 

Roam 12 months: postural sway standing with waist high support 
In this clip Roan has increased her base of support by leaning against the waist high support surface. Her trunk is tilted forwards and her hips are slightly flexed. Despite the extensive external support afforded by her position, you can see the continuous small range movements of the pelvis along with the larger movements associated with adapting her weight distribution as she reaches for toys. 

Implications for practice 
The AIMS Stand Subscale provides a useful description of the increasing control of stability and balance in supported standing over time and with experience. However it does not provide insight into the process by which infants progress from one item to the next, or the underlying balance and stability abilities that underpins this progress

References 

Carpenter MG, Murnaghan CD, Inglis JT. Shifting the balance: evidence of an exploratory role for postural sway. Neuroscience. 2010 Nov 24;171(1):196-204. Abstract

"Humans and other species are unable to stand perfectly still; their bodies continuously sway during stance even during concentrated efforts to avoid such movement. Traditionally, this phenomenon has been viewed as an inability of the central nervous system (CNS) to maintain perfect equilibrium because of its reliance on feedback from sensory signals to control corrective ground-reaction forces. Using a novel method to minimize movements of the body during stance without subject awareness, we have made the unique discovery that ground-reaction forces are generated independent of body sway, as evidenced by observations of increased centre of pressure variability when postural sway is minimized experimentally. Contrary to traditional views, our results suggest that postural sway may be used by the CNS as an exploratory mechanism to ensure that continuous dynamic inputs are provided by multiple sensory systems. This novel paradigm has the potential to significantly shift long-standing views on balance, and questions the theoretical basis behind conventional treatment strategies for balance deficits associated with age and disease."

Murnaghan CD, Carpenter MG, Chua R, Inglis JT. Keeping still doesn't "make sense": examining a role for movement variability by stabilizing the arm during a postural control task. J Neurophysiol. 2017 Feb 1;117(2):846-852  Abstract