Practice and transfer of the frequency structures of continuous isometric force Adam C. King ⇑ , Karl M. Newell Department of Kinesiology, Pennsylvania State University, USA article info Article history: Available online 3 April 2014 PsycINFO classification: 2343 Keywords: Variable practice Time scales Task dynamics Isometric force abstract The present study examined the learning, retention and transfer of task outcome and the frequency-dependent properties of isometric force output dynamics. During practice participants produced iso- metric force to a moderately irregular target pattern either under a constant or variable presentation. Immediate and delayed reten- tion tests examined the persistence of practice-induced changes of force output dynamics and transfer tests investigated perfor- mance to novel (low and high) irregular target patterns. The results showed that both constant and variable practice conditions exhib- ited similar reductions in task error but that the frequency-depen- dent properties were differentially modified across the entire bandwidth (0–12 Hz) of force output dynamics as a function of practice. Task outcome exhibited persistent properties on the delayed retention test whereas the retention of faster time scales processes (i.e., 4–12 Hz) of force output was mediated as a function of frequency structure. The structure of the force frequency compo- nents during early practice and following a rest interval was char- acterized by an enhanced emphasis on the slow time scales related to perceptual–motor feedback. The findings support the proposi- tion that there are different time scales of learning at the levels of task outcome and the adaptive frequency bandwidths of force output dynamics. Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.humov.2014.03.001 0167-9457/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Address: Department of Kinesiology, The Pennsylvania State University, 23 Rec Building, University Park, PA 16802, USA. Tel.: +1 (814) 863 4037; fax: +1 (814) 863 7360. E-mail address: ack196@psu.edu (A.C. King). Human Movement Science 34 (2014) 28–40 Contents lists available at ScienceDirect Human Movement Science journal homepage: www.elsevier.com/locate/humov