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What is Low Muscle Tone vs. High Muscle Tone?

low muscle tone autism

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Muscle tone is defined as the amount of tension in the muscles during rest or movement. Basically, our muscles are never fully relaxed or fully contracted. Even if we’re lounging on the couch, muscle tone makes sure that our muscles don’t relax too much.  If they did, we would lose control of our posture, balance, and motor control. 

On the other hand, if we’re lifting weights, muscle tone makes sure that our muscles don’t contract too much. If they did, we wouldn’t be able to re-straighten our arms after doing a bicep curl.

Muscle tone helps our muscles muscle tone is responsible for the fact that we can stand up straight, maintain our balance or posture, and perform our daily activities. For most of us with typical muscle tone, our muscle tone helps us stay in equilibrium; we can go about our days walking, bending, stretching, and pulling with our muscles doing what we need them to do. 

High muscle tone can be seen in many conditions such as cerebral palsy, while low muscle tone can be seen in Down Syndrome and even autism.

While these are the most commonly recognized conditions that display tonal issues, high and low tone can be present in kiddos with many different types of conditions.

The best way to understand typical muscle tone is to understand high and low muscle tone, otherwise known as hypotonia and hypertonia. Let’s dive in.

Hypertonia, or High Muscle Tone

High muscle tone, or hypertonia, is characterized by extra resistance to movement. This often results in very stiff muscles and challenges with bending and straightening. Think of it as having “too much muscle tone;” too much tension and resistance to movement. This makes it hard to stretch and lengthen the muscles.

One of the more commonly recognized conditions where hypertonia is recognized is cerebral palsy. 

You may have noticed that a lot of kiddos with CP keep their arms and legs tucked in and their hands curled into fists. This is not on purpose. Instead, this is a result of high muscle tone. A lot of these kiddos see occupational and physical therapists for regular stretching sessions.

With high muscle tone, the muscles are contracting more than they should be.

Here are some signs of hypertonia:

  • appears to be rigid and hard to stretch out
  • difficulty bending
  • difficulty reaching out hands, legs, and arms and turning head
  • flexed feet
  • walking on straight legs

Hypotonia, or Low Muscle Tone

Low muscle tone, or hypotonia is characterized by muscles that look “floppy.” If high muscle tone is about having too much muscle tone, low muscle tone is about having too little muscle tone. For kiddos with low muscle tone, their muscles are more lengthened than is typical. This makes it challenging for their muscles to be as tense or resistive as needed to maintain posture and do daily tasks. Imagine trying to stand up straight if your muscles were “floppy” and lacking the support you needed to use them properly.

Infants with low muscle tone often miss important developmental motor milestones like lifting their heads. Some infants that are born prematurely will show signs of hypotonia that they will grow out of as they develop. Hypotonia that continues past the infant years can often be seen with cerebral palsy, Down Syndrome, and other conditions that are impacted by the sensory motor system.

Here are some common signs of hypotonia:

  • seem “floppy” when held
  • have a hard time sitting upright
  • hypermobility, or very flexible
  • appears to be weak
  • can easily dislocate their arms or legs

Low Muscle Tone Doesn’t Mean Weak

A child with hypotonia is not always weak. Though they often exist together, they are not the same thing.

Weakness refers to the strength of the muscles. On the other hand, hypotonia refers how stable the muscles are to begin with. A muscle with low tone has low resistance to movement and always seems “relaxed.” No matter how many bicep curls a person with low tone does, coordinating that movement will be challenging.

While they are not linked, a child with hypotonia can become prone to weakness since movement is all that much harder and takes a lot of effort to engage in.

Would you want to go to the gym to do bicep curls if it was 10x harder? Bicep curls are hard enough. Completing daily tasks can be challenging for kiddos with low muscle tone. This inactivity can lead to weakness, as the muscles aren’t being worked. Working with an occupational or physical therapist can help kiddos continue to use their muscles, even when they don’t feel inspired to do so, in an effort to prevent muscle weakness.

Low Muscle Tone in Autism

It often surprises people that low muscle tone can be seen in kiddos with autism. In fact, studies have shown that the correlation is high enough between these two conditions that seeing low tone in infants should be considered a potential red flag for autism.

While the jury is still out on the causes of both autism and hypotonicity, the link between the two could have something to do with impaired neuromotor functioning. This is why kiddos with autism can sometimes be also diagnosed with dyspraxia. In a 2016 study, 6.9% of those with autism reported having dyspraxia as well.

Hypertonia and Hypotonia Exist on a Spectrum

As with every condition, hypertonia and hypotonia come in varying degrees. While one kiddo may struggle with high or low tone from birth, another kiddo may only show slight symptoms later in development.

No matter how your child’s tone is presenting, it’s important to connect with your pediatrician to discuss appropriate forms of treatment. If you’re already working with an occupational or physical therapist, be sure to ask them about your child’s tone and what strategies you can implement at home to help.

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