A Method to Examine Passive and Active Force Production, and their Correlations with Muscle Morphological Parameters for Healthy Children

Abstract: Muscle morphological and mechanical properties play a crucial role in explaining the mechanisms underlying the development and progression of muscle weakness, joint stiffness, muscle contraction, and the resultant loss of motor function in children. Information in the literature about how muscle architecture correlate with muscle force production in passive and active conditions in children is very limited. Therefore, new information regarding muscle mechanics and morphology has the possibility to contribute to the improvement of more targeted and more effective treatments for children. The goal of this project is to develop a feasible experimental method to examine passive and active muscle force production capacity in the lower limbs in healthy children and to analyse the correlations of muscle morphological parameters obtained from diffusion tensor images(DTI) and force generation capacity in passive and active conditions. For this project, 10 healthy children were recruited and tested in Astrid Lindgren Children’s Hospital, Karolinska University Hospital. The chosen muscles to examine was medial gastrocnemius, soleus, and tibialis anterior. Neuroflexor device was used for the passive force measurements. A fixed version of a hand-held dynamometer was utilized for the active measurements. In order to capture the muscle activities during the movement, surface electromyography was collected simultaneously. The findings from both measurements gave consistent results. In terms of the passive resistance force measured by NF, the characteristic force peaks can be further analyzed to separate different contributions for more informative results. Regarding the correlations, stable and high correlations were determined between the volume(v) and both force measurements except the medial posterior SOL for MVC. Fascicle length (FL) correlations showed more of a variety since high correlation was observed for PF and FL while negligible correlation was found between P3 and FL. Further research with more parameters is needed to obtain more reliable results. Overall, not only healthy subjects but also children who suffer from muscle weakness and disabilities should be investigated for further examination.