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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 webmanual.skillsforaction.com/low-muscle-tone

New Feb 2013 

Creating Action Spaces 

The difficulties experienced by children with a diagnosis of low muscle tone

• May be late learning to sit and walk - but not always
• Have trouble sitting erect and working at a table - tend to sit with back rounded, may lean on one hand when drawing and writing
  Have difficulty sitting still, tend to fidget, not complete school tasks
• May tire very quickly, not like walking far, have trouble going up stairs
• May be good at games that involve short bursts of running,  but have difficulty with posture in sitting, drawing and handwriting - these tasks require sustained activity in the postural muscles
• Sit between legs on floor (w-sitting), do not like cross legged sitting
• Appear to have poor attention span or concentration, give up easily
• Cannot hang on the monkey bars, do not like climbing on the jungle gym, are fearful

What causes these difficulties?

The most common cause of these difficulties is joint hypermobility  associated with a cautious temperament.

In individuals with hypermobile joints (loose or lax joints) the connective tissue structures that hold the body together have more give (are more easily stretched) than usual. This means that the muscles must work harder than usual to hold the keep a good posture and move. 

Children with a cautious temperament  are often quite anxious  which leads to avoidance of tasks that require effort and a tendency to give up very quickly. This in turn leads to low levels of activity, weakness and poor endurance. 

Read more here about the link between joint hypermobility and low tone 

What is low muscle tone?

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. 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).

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

The clinician makes a judgment about a muscles 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  

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 fibre, 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.

Muscle tone, alertness and readiness for action

The term muscle tone is also used to describe the a muscle's readiness for action.  This 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.

Can low muscle tone (muscle laxity) be "cured"

The general stiffness of a child's muscles - which is what provides the muscles' tone, depends on two factors:

The stiffness in the connective tissue - this is genetically determines (it is in the DNA) and cannot be changed.  (See  Joint Hypermobility Syndrome)

The size of the titin molecules in the muscle cells. Stronger muscles have larger titin molecules. Stronger muscles have better tone.

Muscle and joint laxity cannot be "cured". But the movement difficulties  associated with muscle and joint laxity can be improved by  training to improve muscle strength, flexibility, endurance, coordination and attention. (TAMSKA).  See Help for low muscle tone

Underlying causes of low muscle tone (muscle laxity) and poor alertness for action

Joint hypermobility syndrome – The connective tissue is more compliant than usual, leading to joint and muscle laxity and weak muscles

• Intervention:  Exercises to improve strength and endurance and train posture and coordination

A cautious nature – The child avoids  tasks and activities that are difficult or require physical effort, which affects engagement and readiness for action.

• Intervention: providing the child with tasks that challenge them in such a way that they become less avoidant and learn courage

Muscle weakness – as a result of lack adequate opportunities for engagement in activities that load the muscles in a way that leads to increased muscle strength

• Intervention:   an exercise training programme that provides the child with appropriate challenges to learn new skills and engage in challenging tasks that load the muscles in a way that increases muscle strength.

Developmental coordination disorder where a child has difficulty learning new skills through experience and exploring ways to perform new and challenging tasks, leading to avoidance and lack of experience.

Intervention: a movement training programme that provides the child with opportunities for learning new skills in a structured way.

Autism - when it is associated with joint hypermobility and and associated laxity in muscles.

Down syndrome where joint hypermobility and muscle laxity is a defining feature.

Creating Action Spaces 

Help for low muscle tone

The only way to improve muscle tone is to strengthen the muscles, increase endurance and improve the child's levels of readiness for action.

This can be achieved by providing the infant or child with many different opportunities for  engaging with physical and mental action that require effort and challenge the child.

More about babies with joint hypermobility and associated low muscle tone
The TAMSKA 20-minutes-a-day challenge 
How you can help your child - starting today
​Fit for action: An Online Guide for Parents and Teachers