I've decided that the best way to try to explain what Hypotonia is will be to break it down into separate postings:
Hypotonia is defined by the Children's Hospital Boston simply as, "decreased muscle tone" that "can be a condition on its own, called benign congenital hypotonia, or can be indicative of another problem..." This differs slightly from the John Hopkins Hypotonia Clinic that states within the first sentence that, "Hypotonia is not a diagnosis, rather it is a symptom of diminished tone of skeletal muscle associated with decreased resistance of muscles to passive stretching." Being a parent of a child that, at this point, has no determined cause for Rae's Hypotonia, I am inclined to slightly disagree with the John Hopkins definition. So, let's break this down...I promise I will try to leave out as much medical mumbo jumbo as possible.
Here's what low muscle tone is not...
Prior to Rae's diagnosis, I only heard the term "muscle tone" on television or in exercise informercials where someone was pointing to parts of a fit and trim woman's body stating they needed to "tone up." The implied purpose of toning was to make a person's body more defined and sculpted. This idea is a myth. Muscle tone has NOTHING to do with a persons physical appearance. The correlation between muscle tone and physical appearance was created to make the idea of developing muscle mass more palatable for women who didn't wish to look like a professional body builders. According to Matt, who offers an in-depth explanation of "toning," at AnswerFitness.com, a toned body is, "simply low body fat coupled with muscle mass." The fitness world's use of the word "tone" doesn't correlate with the medical world's definition. So, my initial confusion is somewhat understandable considering my base knowledge was gleaned from late night exercise infomercials and wanna-be model programming.
So, what is muscle tone and how does it work?
Merriam Webster defines muscle tone or tonus as:
"A state of partial contraction that is characteristic of normal muscle, is maintained at least in part by a continuous bombardment of motor impulses originating reflexly, and serves to maintain body posture..."Well if you're anything like me that is a little bit too clinical and doesn't clearly explain what muscle tone does. I offer another explanation of muscle tone from About Cerebral Palsy.org that may help break it down better:
"Muscle tone refers to the amount of tension or resistance to movement in a muscle. Muscle tone is what enables us to keep our bodies in a certain position or posture. Changes in muscle tone are what enables us to move. For example, to bend your arm to brush your teeth, you must shorten (increase the tone of) the biceps muscles on the front of your arm at the same time you are lengthening (reducing the tone of) the triceps muscles on the back of your arm. To complete a movement smoothly, the tone in all muscle groups involved must be balanced. The brain must send messages to each muscle group to actively change its resistance."Okay, now that we have a better understanding of what muscle tone does, controlling our physical movements, we can get a better sense of what parents of children with Hypotonia are trying to overcome on a daily basis. To paraphrase John Hopkins, the muscles are taking a longer amount of time to respond to "contraction stimuli" (bend arm, lift head) and as a result are often not able to maintain the contraction for long periods of time. This causes them to lose control and go kinda limp like cooked noodles (my words) and is the reason people also call low muscle tone "floppy infant syndrome."
So, as a normally functioning adult, when I decide I want to lay on my tummy and prop myself up on my forearms it doesn't require much effort. Without any real thought or difficulty my brain sends a message to my muscles, my muscles take the appropriate actions, and I am quickly in the desired position. It is the opposite for our daughter Rae. She is placed in this position by an adult, propped up on her forearms, her head wobbles from side to side (lack of head control), her arm muscles start to become tired after about 5-10 seconds, her head becomes too heavy to hold up, her muscles release, her head drops, and after this cycle repeats itself a few times she becomes exhausted and will sprawl out on the floor like a backwards Vitruvian man. With time her endurance will steadily increase, but it is a long developmental process with no guidelines of "normalcy".
The video below was taken when Rae was 13 months old.