Generalized modules reflect similar biomechanical subtasks across skipping and running

Biomechanical and metabolic differences between skipping and running suggest the nervous system may require an alternative motor control strategy to execute skipping. Motor control strategies can be compared across gaits by muscle modules based on which muscles are coactivated (module composition) and whether the same module compositions are used across gaits (module generalization). The purposes of this study were to identify and compare the module composition of skipping and running and determine the module generalization present across these two gaits. Six healthy young adults performed 10 s skipping and running trials on a treadmill at 2.5 m/s while electromyography (EMG) was collected from 8 muscles. A non-negative matrix factorization extracted motor modules from the EMG data. Generalization of modules, both at the group and individual level, was determined with correlations of module weights. Participants required 3.7 ± 0.5 (range: 3-4) modules to control skipping and 3.8 ± 0.4 (range: 3-4) modules to control running. Three generalized modules were found across gaits at the group level, and at the individual level each participant had at least one generalized module. The generalized modules contributed to similar biomechanical subtasks across gaits, highlighting similar gross motor task demands. The unique biomechanical demands of the skipping hop resulted in gait-specific control of the tibialis anterior and gluteus medius. Future work is needed to identify the factors that influence the amount of generalization an individual uses across locomotor tasks and whether the degree of generalization impacts the performance of each gait.