As Physical Therapists, we are “Movement Experts”. This is our domain of expertise. No argument.
I recently posted a video of a TED lecture given by Daniel Wolpert entitled “The real reason for brains“. In Wolpert’s discussion, he argues that the primary reason for the brain is movement. He provides several examples to support this and to say the least, it is quite thought-provoking. While I am going to discuss the intricacies of movement in this post, I am not attempting to argue why we move. I simply want you to deeply consider and appreciate the beauty of how we move. From the brain to the muscles, an orchestrated series of events must occur to facilitate movement. And I want you to appreciate, it’s much more than muscles and bones.
To put things into perspective…
Bi-pedalism is a defining characteristic of human movement. It is the concept that we ideally move upon two legs, defined by a stance and swing phase. We are one of the few animals to choose this transportation means (others will use this technique temporarily to perform certain functions such as reaching for food or hiding from predators) but it is unclear how or exactly why this happened. Some have hypothesized that we gained this trait to assist with energy conservation, to carry objects, utilize tools and see over tall objects.
This video makes gait look and sound very simple. Heck, he can describe it in less than 5 minutes. But let’s consider the Honda ASIMO. ASIMO is considered by many to be the most advanced humanoid robot. Honda began developing ASIMO in 1986, and since, has improved its balance, agility and overall functionality. 27 years later, observe the video below.
Despite the amount of time, money and technology invested, ASIMO’s gait does not resemble a human’s. So what makes us different? What makes it so difficult to make ASIMO walk like us (I can see where they are going, but 27 years later, this robot still walks like a robot).
I would argue that ASIMO walks like a robot because he lacks a complex, interactive nervous system. For example, he has joints. He has joints which were built to resemble ours. And despite this, he still does not walk “human”. He is also able to generate power. Despite having more plastic than “meat” (ie. muscle), this power represents the force generation of our muscular system. But despite generating force through human-like joints, he walks robotic-like. Get where I am going? It has to do with our complex nervous system and the abstract connection that our individualized nervous systems have with our environment.
Where movement begins…the brain:
Pre-Frontal Cortex: Anterior to the motor and pre-motor cortices of the brain, this region of the brain is most notably responsible for “executive function”. It does alot of really cool stuff but in terms of movement, it is responsible for planning for the execution of an action. For example, if I ask you to highlight this sentence with your mouse pointer, the pre-frontal cortex will formulate a plan to execute the movements necessary to complete the task.
Posterior Parietal Cortex: While the pre-frontal cortex is planning the execution, this portion of the brain works to figure out where the body part (which will soon be moved) is in space (a baseline reading per se). It also helps assess any objects it may come in contact with in the external environment. To do this, it relies on information from sensory systems which interpret vision, sound, and somatosensation. So in our example above, the posterior parietal cortex may determine that the hand is resting on your desk and that it must move around a glass of water to come into contact with your mouse.
The Premotor Cortex, Supplementary Motor Area and Cerebellum continue to plan…
Pre-motor Cortex: This portion of the brain lies within the frontal lobe, anterior to the primary motor cortex and helps “guide” movement. It is made up of a lateral and medial portion. The medial pre-motor cortex helps plan and coordinate movement through internal cues (ie. memory). The lateral pre-motor cortex is more involved in organizing and selecting movement based upon external cues, such as vision. Side note: This portion of the brain contains “mirror neurons”. Mirror neurons are neurons that fire when we observe and mimic (“mirror”) the behavior of another human or animal. These exist in the pre-motor cortex and are said to be central to our self-awareness (Read This) and have roles in empathy, language, expression, etc. It has been said that when we yawn, after seeing someone else yawn, it is due to activation of these as an empathetic response. It has further been thought that a deficiency in these lead to the symptoms we see in those with autism, who have a difficulty in formulating motor learning, empathy and language.
Supplementary Motor Area: This will kick in to deal with more complex movements which may involve the using of bilateral limbs…In the example above, we are just moving one hand so it may not need to activate…
Cerebellum: This portion of the brain will fine tune the coordination of movements, so that the final movement appears nice and smooth. Below is an example of what will happen if this critical phase does not occur…
Motor Homunculus: This portion of the frontal lobe contains a “roadmap” of the body (The cortical representation of each portion of the body is not truly proportionate to the size of the body part in which it represents). The larger representations deal with more intricate motions required to move that body part (ie. The hand is quite large compared toe the arm due to the complex series of motions necessary to move the hand/fingers).
Primary Motor Cortex: The name gives away the importance of this portion of the brain. Located in the frontal lobe, the primary motor cortex generates the neural impulses required to control the execution and force required for the necessary movement. Once a neural impulse is generated, it crosses mid-line to activate movement in structures on the opposite side of the body (ie. The right hemisphere controls left side movement). Finally, movement is starting to take shape…Info is sent down the spinal cord via spinal and interneurons and we are getting closer to muscles…
While this is only a very basic explanation of a much more complex process, I hope you can consider all of the really important stuff that happens before you move. I often hear from colleagues that we are musculoskeletal experts… We ARE NOT musculoskeletal experts. We ARE movement experts. This is a much more comprehensive role which involves a consideration of the neurological, musculoskeletal, psychological, and social domains. In the scheme of things, if we just had muscles and bones and a simple execution system, we would move like ASIMO. Thank god we are more dynamic.
If you don’t believe me, Check out a dance-off between a great blogger, BBOY SCIENCE himself, Tony Ingram and ASIMO…AND DONT FORGET TO GIVE ME, THE BBOY, AND OTHERS A VOTE OVER AT THERAPYDIA.COM BLOG AWARDS…Enjoy!!!