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Quantitative assessment of co-activation, muscle weakness and functional ability in patients with different neurological conditions

Researchers

  • Dr. Monica Busse
  • Prof. Mark Wiles (School of Medicine (Neurology), Cardiff University)
  • Dr. Robert van Deursen

Muscle weakness and co-activation in individuals with neurological disorders has been suggested to contribute to loss of function. Co-activation may be considered normal or at times counter-productive to function. The aim of this study was to investigate whether antagonist co-activation is related to weakness or the site of the neurological lesion and whether it impacts on function and activity.

Five groups of patients with weakness due to extra-pyramidal disorder, namely Parkinson’s disease (PD), pyramidal tract disorder, lower motor neuron/ peripheral nerve disorder or muscle disorder were recruited. A matched healthy control group was also recruited. Measures of isometric quadriceps and hamstrings strength and co-activation (isometric and sit-to-stand (STS)) were obtained. Co-activation of hamstrings during knee extension was calculated as a ratio of hamstrings over quadriceps activity. Kinematics of STS, gait speed, Rivermead Mobility Index and long term activity monitoring provided measures of functional abilities. Between group differences as well as associations were explored.

All patients were significantly weaker than healthy subjects. Co-activation was not different from the matched control groups, except in patients with PD. All neurology subjects were slower to stand up and walk than controls. Mean 7 day step count was significantly lower. Self-selected gait speed was a significant predictor of actual walking mobility. A trend of higher co-activation in the presence of weakness was identified independent of diagnosis; isometric co-activation was negatively correlated with quadriceps strength (r= -0.45; p=0.001) in neurology patients.

Antagonist co-activation is related to muscle weakness in neurology patients. Co-activation appears to not be related to the particular neurological pathology but rather to muscle weakness. Muscle weakness rather than co-activation is associated with mobility restrictions. The findings of this study suggest that emphasis in therapy should include some focus on compensations or alternative solutions that optimise function and promote independent living.