Have you ever thought about how many things happen in your body when performing a simple motion in daily living? Even something like walking, wandering around your own house; it seems simple, doesn’t it? But you were not able to do it when you were a baby, and it took a long time for your brain to mature, to learn how to exploit senses and actuate muscle, and to program a motion pattern that most people perform daily without even thinking about it.
If you never thought about it, just consider how much effort and expertise and time it took for engineers to produce robots, which can replicate a seemingly functional gait pattern, but are still far from the performance of a human being. From this perspective, the process of motor learning is fascinating, wonderful and intriguing.
Learning to move
Engineers are usually interested in control laws, constraints, power efficiency and all those tech-sounding terms that belong to the domain of automation, of course. But if you add to all this the fact that the ‘robot’ is made of biological tissues, grows and autonomously learns and programs itself, the whole thing becomes even more intriguing, fascinating and astonishing. This is the perspective of a biomedical engineer, trying to sort out how a human being learns how to move from scratch.
Understanding human motor control is certainly not an easy task! Humans are not robots with pre-defined equations and programmed instructions.
Understanding human motor control is certainly not an easy task! Humans are not robots with pre-defined equations and programmed instructions. Thus, we thought that the best way to deepen our knowledge of human motor control was to observe how it builds up during growth. Well, observe it like engineers do, that is, using quantitative measures and mathematical descriptors.
When you accept the challenge to study motor control development, you will learn soon that there is a multitude of influencing factors, often operating in conjunction: these factors can be either within the individual (e.g. neuromotor maturation, growth rate, sensitive learning period) or in the environment (e.g. bonding, stimulation). Thus, given the multitude of influencing factors, the correspondence between factors and effects on motor development and motor control is difficult to investigate.
This is the reason why in this work we investigated the effect of adolescents’ growth spurts on walking performance. During adolescence, walking is theoretically a well-achieved fundamental skill, having reached a mature manifestation; on the other hand, adolescence is marked by a period of accelerated increases in both height and weight, referred to as a growth spurt.
What did we do?
It is indeed common to observe low gross motor coordination in this population: a growth spurt can affect the output of motor controller, which was previously organized on different body segment dimensions.
This period was chosen as a controlled and natural environment for partially isolating one of the factors influencing motor development: segment growth.
The aim of the study was to compare gait performance of growing and not growing male adolescents
The aim of the study was to compare gait performance of growing and not growing male adolescents, in order to study which are the modifications that motor control handles when encountering a sudden change in body segment length.
As engineers, we wanted to look at this problem with the rigorous approach of biomechanics and human movement analysis and not just with observational methods: wearable inertial sensors were used to evaluate quantitatively gait performance of the analyzed participants.
What did we find?
The findings of the present work suggest that, as could be expected, a growth spurt during adolescence affects variability, smoothness and regularity of gait, showing growing adolescents as more variable and less smooth and regular than their not growing peers.
Sudden peripheral changes of the body happening in growing adolescents affect movement performance
On the other hand, they show that a growth spurt does not affect gait stability. This means that sudden peripheral changes of the body happening in growing adolescents affect movement performance in the analyzed population, but gait control of young healthy growing subjects is able to handle these modifications, maintaining a level of gait stability close to their not growing peers.
It is relevant to point out that, in the literature, gait variability is often intended as an indirect assessment of stability, hypothesizing that if you are more variable while walking, you could be at a higher risk of falling. These results highlight that this is not always true, in particular in healthy young subjects, because central control can handle variable gait manifestations, as a response to perturbations, in a controlled and stable way, without increasing the risk of falling.