Personalized spatial recruitment model to motor unit type and number

Efficient computational models should incorporate realistic features for reliable results when investigating specific scientific questions. The present study investigates how a useful and widely used Motor Unit (MU) pool recruitment model design impacts simulation results for a particular realistic case: aged Biceps Brachii (BB) muscle. This study: 1) examines how the use of generic MU recruitment model (Fuglevand model) can distort the recruitment rate of faster Motor Units (MUs) for aged BB muscle, and 2) proposes a new type-scaled model based on discrete property ranges for different MUs types. The results show that generic MU recruitment models confusing size and type of MUs can deliver a non-realistic recruitment behavior for particular cases: elderly people. Additionally, such models are not appropriate for mixed, reversed, and type-discrete recruitment orders observed in animal and human acquisitions. The new proposed model recruits higher number of fast MUs at higher force ranges than the orderly size recruitment. This aspect increases muscle efficiency with more realistic prediction of surface Electromyogram and force generated using models.