Introduction:
Amyotrophic lateral sclerosis (ALS) is a terminal neurodegenerative disease, which gradually damages motor neurons in the cortex, brainstem, and spinal cord, leading to a progressive deterioration in patients’ fitness and their dependence on others.

Aim of the research:
To assess electromyographic parameters and abnormal gait in the course of ALS.

Material and methods:
The study covered 20 people with clinically proven or probable ALS diagnosed, determined according to the El Escorial criteria. In the study group, 10 patients were affected by the limb onset of the disorder, and the remaining 10 people by the bulbar onset. The analysis covered electromyography and test results: 6-minute walk test and 10-metre walk test performed three times within 6 months.

Results:
The results of electromyographic parameters and tests were analysed for the whole group and separately for the group with bulbar-onset and limb-onset ALS. The statistical analysis of the results has shown that the duration of motor unit potential (MUP) is the most useful electromyographic parameter in early diagnosis and monitoring of the course of the disease. The increasing abnormal gait in the course of ALS was a clinical reflection of gradually prolonging MUP.

Conclusions:
The progressing loss of nerve and muscle function as a result of motor neuron loss is reflected in walking deterioration in ALS patients. 2. The gradually increasing MUP duration of particular muscles is concomitant to the increasing abnormal gait. The assessment of the MUP duration of particular muscles may serve to monitor the ALS progression.