Coordination

What is coordination?

Successful movement involves the complex coordination of multiple joints and muscles which is achieved via the appropriate sequencing, timing and grading of muscle recruitment (Shumway-Cook and Woollacott 2007; Berthier et al. 2005). Even a simple reaching task involves all levels of the central and peripheral nervous system with the integration of these sensorimotor systems occurring primarily in the cerebellum (S2.12) (Fuller 2004). Smooth accurate movement involves the interaction of hand–eye coordination, inter-limb and trunk coordination.

Incoordinated movement

Incoordination presents as a lack of smooth sequenced movement which is often awkward and uneven and may involve both limb and trunk muscles. The incoordination is attributed to a loss of synergistic interplay between muscles as a result of disruption in muscle:

As the control facilitating coordinated movement is highly complex and involves many nervous system structures it follows that incoordination can be a consequence of damage to any one of them. This includes:

• Cerebellum (S2.12)

• Motor cortex (S2.7)

• Basal ganglia (S2.11)

• Sensory feedback: Proprioception (S2.23) or vision (S2.10 and S3.27)

• Motor output: Altered muscle tone (S3.21) or muscle weakness (S3.30).

Ataxia is a term used to describe the motor incoordination presented by patients with a deficit affecting the cerebellum (S2.12) during voluntary movement. It includes symptoms such as nystagmus, reduced manual dexterity, poor balance and altered gait (Bakker et al. 2006; Ilg et al. 2008), dysarthria and dysmetria (Thoma et al. 2008). Dysmetria, is a problem with judging the distance of movement and is often referred to as intention tremor. The outcome is inaccurate movement with overshooting (hypermetria) and undershooting (hypometria) during the task. Ataxia can affect the trunk (trunk ataxia) or limbs (limb ataxia) or both, depending on whether the lesion is in midline or the cerebellar hemispheres, respectively. The incoordinated movement that is produced affects mobility, when the patient presents with a drunken swaggering gait and all other functional activities. Ataxic movement is thought to occur due to impairment in the timing and duration of muscle activation, or the magnitude and grading of force production (Ausim 2007).

Caution