The underlying neuromuscular mechanisms contributing to muscle weakness and their interaction with gait

Muscle weakness is one of the most common symptoms in children with cerebral palsy (CP) and children with Duchenne muscular dystrophy (DMD). Muscle weakness in CP is caused by alterations in motor control due to the brain lesion (neural component), and changes in muscle morphology (non-neural component). In children with DMD, muscle weakness is mainly non-neural and caused by changes in intrinsic muscle morphology. The altered gait pattern in children with DMD is not well defined and even though muscle weakness is theorized to be the main cause of DMD gait, there are no studies assessing the relationship between weakness and the pathological gait pattern of children with DMD. Contrarily, the pathological gait patterns in CP are well known. However, although several researchers studied the association between muscle weakness and altered gait, no consensus on this relationship could be reached. This lack of agreement could be attributed to the methodological differences between the studies. Further, the test positions employed during the weakness assessment were not related to the joint angles (and thus muscle lengths) of gait. Additionally, assessor strength and compensation mechanisms had an influence on the strength measurement outcomes, which could also have contributed to the lack of consensus between findings of the previous studies.

The overall aim of this PhD project was to analyze how muscle weakness is related to the altered gait pattern of children with neural and neuromuscular diseases, and to study the underlying neuromuscular mechanisms contributing to muscle weakness and their interaction with gait.