Investigation of Muscle Synergies Using Four Different Methods of Synergy Extraction While Running on a Treadmill in Beginner Runners

The study of muscle synergy is a new way to evaluate the functioning of the human body's control system. Different mathematical methods are used to extract muscle synergies from electromyographic data, and this factor can cause different outputs in muscle synergies. Therefore, the aim of this study was to investigate muscle synergies using four different synergy extraction methods while running.

In this semi-experimental study, 12 male novice runners participated. Electromyography activity of rectus femoris, vastus medialis, vastus lateralis, biceps femoris, semitendinosus, medial gastrocnemius, soleus and tibialis anterior were recorded during running on treadmill. In order to extract muscle synergy, the methods of non-negative matrix analysis algorithm, absolute value of principal component analysis, independent component analysis and factor analysis were used. Pearson correlation method was used to measure the similarity of the extracted patterns and ANOVA Repeated Measures were used to compare the relative weight of muscles (P <0.05).

Patterns of muscle synergy using different extraction methods showed low to high similarity. Muscle synergy activation time and synergy peak points were different. The relative weights of internal, external, and twin broad muscles were significantly different (P <0.05). Four muscle synergies were obtained from electromyographic data by inclusion of variance.

According to the results of this study, it was observed that different methods in extracting muscle synergy can have a great impact on the number of synergies extracted, the pattern of synergies and the relative weight of muscles, the time of activation of synergies and peak synergy and thus cause different interpretations in studies.