My child has been diagnosed with low muscle tone. What does this mean?

Who gets a diagnosis of low muscle tone?

An infant or child will get a diagnosis of low muscle tone when:

  • The muscles appear to be less firm than usual
  • The child appears to be floppy and to have loose joints
  • The child appears to be less alert and have poor posture and attention

For a more technical discussion please see Rethinking Low Muscle Tone

Often a child will get a diagnosis of low muscle tone because of one or more movement difficulties

Infants and low muscle tone

An infant who is very floppy or limp at birth may get a diagnosis of infant congenital hypotonia. But mostly infants are said to have low muscle tone when they are less active, are slow to reach the major milestones or sitting, standing and walking, sit with a rounded back, hate tummy time and tend to be very sensitive or fearful of new people and situations. 

Read more: Low muscle tone in infants and toddlers 

Low muscle tone does not cause any of these behaviors or motor difficulties

The first thing to understand is that low muscle tone is a not a condition or a diagnosis. There are a number of conditions that affect the brain and muscles where hypotonia (low muscle tone) is a symptom.  The child appears to be floppy and there are other signs and symptoms that indicate that the child has a neurological disorder including significant developmental delay, altered reflexes and cognitive difficulties.  

Low muscle tone is not a diagnosis 

It is important to understand that low muscle tone should never be used as a diagnosis.

  • There is no health condition called low muscle tone.
  • There are no diagnostic criteria to describe such a condition. 
  • Low muscle tone cannot be measured.

Nowhere will you find a good reason for why your child has low muscle tone. You will also not find any effective treatment being described.

So why did my doctor or therapist say that my child has low muscle tone? 

The term "low muscle tone" is still widely used by doctors, physical and occupational therapists. This is because for many years the reason why children, with no identified muscle or neurological disorder, presented with movement and postural difficulties, developmental delay and weakness, was not well understood.

Today, however, the impact of joint hypermobility on muscles, posture and movement and even on behavior is well documented. We also know that a muscle's tone comes from a the giant muscle protein called titin. 

Some health professionals have simply not caught up with current thinking.

For a more detailed and referenced argument about the misuse of the low muscle tone diagnosis and the importance of titin see: Rethinking Low Muscle Tone 

If it is not low muscle tone, what is causing my child’s movement difficulties?

The majority of children who have been labeled as low toned usually have one or more of the following fairly common underlying conditions: generalized joint hypermobility, developmental coordination disorder, associated with a very cautious, fearful nature. 

Joint hypermobility is the most common cause of low muscle tone

Joint hypermobilityis probably the most common condition that causes the difficulties experienced by children with a diagnosis of low muscle tone.

Joint hypermobility simply means that structures that hold the joint together are more pliable than normal and provide less support for the joints.

However, in most instances strengthening the muscles not only provides the added support that joints need for good posture and movement, but also increases the inherent stiffness in the muscle and joint connective tissue. 

There is one other very important aspect of joint hypermobility. Despite the increased flexibility, the child will usually have some tight muscles. This is the reason why children with generalized joint hypermobility have tightness in the hip muscle, including tight hamstrings and tightness in the muscles that cross from the lower back over the side of the hips. this tightness makes sitting erect difficult. and uncomfortable. 

So for most children with a diagnosis of low muscle tone, the best approach to improving posture and motor control is a program of exercises to strengthen weak muscles on the one hand and stretch tight muscles on the other. A fitness training program is particularly important for inactive children who are at risk for obesity and low bone density.  

Developmental coordination disorder (DCD)

There are a group of children who have difficulties with coordination and with learning new skills which affects their function and participation at home, at school and in the playground. 

Children with DCD have difficulties with the control of posture, with balance and agility tasks as well as fine motor activities and handwriting. They may also avoid participating in playground games and as a result have poor fitness levels.

Research has shown that the most effective approaches  to improve the coordination of children with DCD are task based intervention programs which target specific skills. A recent systematic review of the efficacy of different approaches to intervention for children with DCD concluded that task based approaches, including CO-OP and NTT are more effective than process oriented programs such as sensory integration therapy (SIT) and neurodevelopmental therapy (NDT). 

A very cautious/anxious nature: the highly sensitive child

Children with low muscle tone, joint hypermobility and DCD often have a very cautious and sometimes fearful nature, leading to a raft of emotional and behavior difficulties which interfere with everyday and school function. 

Recognizing and understanding the impact of fearfulness and anxiety on behavior allows parents to implement strategies to help their children overcome their fears and learn to take on challenges. Read more

Low muscle tone is not caused by a sensory processing disorder

Children who have been given a diagnosis of low muscle tone, also often have are diagnosed with a sensory processing disorder.  However there is no valid scientific argument that links muscle tone to disordered sensory processing. Read more  

Recognizing joint hypermobility

Elbows and knees bend backwards.

elbow extension.jpg

 

Child may have a hollow back and flat feet, and poor standing posture. 

Child-stand-hollow-back.jpg    

Wrist and finger joints bend further than usual. 

       hypermobile hands_2.jpgwrist flexion.jpg

Read more: Joint hypermobility in children  and Infants with low muscle tone and joint hypermobility

Hypermobile joints and tight muscles cause movement difficulties

Sometimes joint hypermobility is missed because the child appears to have tight muscles. It is important to understand tight muscles is a common feature of joint hypermobility, especially in the muscles crossing the back and sides of the hips.  It is also important to understand that this muscle tightness can be an important underlying cause of some of the difficulties experienced by children with a "diagnosis" of low muscle tone. 

Poor sitting posture is usually caused by a mixture of tightness, weakness and sometimes poor coordination.  My child can't sit up straight and fidgets a lot at school. What is the reason?

T sitting slumped_2.jpg

How can I improve my child's low muscle tone? 

The answer is quite simple: implement a fitness training program. 

Muscle weakness is often present in children who are given a diagnosis of low muscle tone and it is the muscle weakness and poor stamina, along with some muscle tightness  that are the real underlying reasons why a child has movement difficulties.  Muscle weakness and poor flexibility improve with strengthening and flexibility exercises. 


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What about infants diagnosed with low muscle tone?

Infants who appear to be floppy, have very lax joints and are slow to reach their major milestones on time are often given a diagnosis of "low muscle tone".   Very often these infants have a combination of pre-mature birth, joint hypermobility, a very cautious nature and sometimes early symptoms of autism.

Whatever the underlying reason for your infant's movement difficulties early intervention is important.  Early intervention helps to prevent the long term impact of developmental delay on attention and coordination difficulties which often surface just when the child enters school. 

Read more: How low muscle tone and hypermobility affect an infant's development

Low tone infants lie with their legs wide apart, and twisted out at the hips. 

2 weeks lying_1.jpg  T 11m prone.jpg

Low tone infant often bottom shuffle and miss the crawling stage Read more 

Iinfant scooting on buttocks     Infant bottom shuffling

Low tone infants have difficulties getting up into kneeling and stand with their legs wide apart. 

More about muscle tone

The term muscle tone refers to two aspects of muscles' structure and function:

  • The inherent stiffness of a muscle - its resistance to being stretched and firmness when palpated (squeezed).
  • A muscle's (or groups of muscles') readiness for action - the muscle's responsiveness to signals from the brain and to sensory feedback.

The term low muscle tone is used when the muscles' stiffness is less than usual (ie it is low) and the readiness for action is also low (muscles respond slowly).

The term muscle tone refers to two aspects of muscles' structure and function.

  1. The inherent stiffness of a muscle - its resistance to being stretched and firmness when palpated (squeezed).
  2. The muscles' readiness for action - the muscle's responsiveness to signals from the brain and to sensory feedback

The term low muscle tone is used when the muscles' stiffness is less than usual (ie it is low) and the readiness for action is also low (muscles respond slowly).

How is a muscle's firmness (tone) tested?

4y stepping over gaps.jpgThe clinician may make a judgment about a muscle's firmness and inherent stiffness by:

  • Squeezing the muscle to feel the resistance to compression
  • Lifting up and moving the limbs and feeling the resistance to this movement 

The trouble with these tests is that they are not reliable and do not provide any useful information.

What determines a muscle's firmness? 

The firmness of a muscle is determined by its inherent stiffness and this in turn depends on the stiffness in the connective tissue sheaths that encase each muscle fiber, hold the bundles of muscle fibers together and connects the muscle to the tendons.

In children with hypermobile joints  the connective tissue is less stiff than usual. (It has more give and is more easily stretched).

This tendency for less stiff connective tissue which results in hypermobile (lax)  muscles and joints is genetically determined. About 10-15% of people are hypermobile.

The other very important structure that that determines a muscle's firmness and resistance to being stretched is the giant molecule titin. 

Titin is a very large elastic molecule found within the muscle cell.  The size and strength of the titin molecules is determined by the  amount of work a muscle is made to do on a regular basis. Strong muscles have larger and stiffer titin molecules - and this makes the muscle firmer and stiffer.  The muscle has better tone.

Generally speaking, strong muscles are firmer and have better tone. It is a common fallacy that you can have strong muscles which are also "low toned".  Strengthening a muscle makes it firmer and changes the form of the titin which is component of a muscle fiber which provides the tension and recoil in the muscle.  

will forward roll 1_0.jpg

Strong muscles always have good "tone"

There is a common misconception that a muscle can be strong and low toned. This is not correct.  Strengthening a muscle increases it resistance to being lengthened and readiness for action.  The elastic muscle protein titin increases in size with training - this makes the muscle less resistant to being lengthened (stretched) and increases its stiffness. Training also increases the strength of the connective tissue components of the muscle as well as the strength and stiffness of the tendons.  

Muscle tone, alertness and readiness for action

The term muscle tone is also used to describe the a muscle's readiness for actionThis is set by the child's alertness,  general level of arousal and readiness for action.  

The brain primes the muscles for action by sending signals to the muscles’ sensory receptors.  In effect the sensory receptors become more alert and provide more effective sensory feedback and respond more quickly. This allows for the rapid adjustments needed for maintaining balance and postural stability.

  • When a child is alert and engaged,  the muscles are primed for action.  The muscle tone is good and the posture is erect.
  • When a child is over-aroused, the muscles may become twitchy and overactive.  This makes the child less able to focus attention on a task.
  • If a child is anxious, finds a task difficult and is having trouble focusing his attention, the normal alertness for action signals do not reach the muscles. They become less responsive and provide less sensory feedback.  Muscle tone is lowered and the child's posture becomes less erect and alert..