Modular Organization of Exploratory Force Development Under Isometric Conditions in the Human Arm

ABSTRACT

Muscle coordination of isometric force production can be explained by a smaller number of modules. Variability in force output, however, is higher during exploratory/transient force development phases than force maintenance phase, and it is not clear whether the same modular structure underlies both phases. In this study, eight neurologically-intact adults isometrically performed target force matches in 54 directions at hands, and electromyographic (EMG) data from eight muscles were parsed into four sequential phases. Despite the varying degree of motor complexity across phases (significant between-phase differences in EMG-force correlation, angular errors, and between-force correlations), the number/composition of motor modules were found equivalent across phases, suggesting that the CNS systematically modulated activation of the same set of motor modules throughout sequential force development.

Keywords:

• electromyography
• force development
• motor coordination
• motor modules

ACKNOWLEDGMENTS

The authors wish to thank Randall F. Beer and William Z. Rymer for the support of data collection and Seng Bum Yoo for assistance with data collection.

Additional information

Funding

The research reported in this publication was supported by the American Heart Association (17SDG33670561; and PI, J. Roh).