title: Low-level intermittent quadriceps activity during transcranial direct current stimulation facilitates knee extensor force-generating capacity.
abstract: Anodal transcranial direct current stimulation (tDCS) is known to increase the force-generating capacity of the skeletal muscles. However, when tDCS is concurrently combined with a motor task, interference may occur that hinders tDCS effects. Here, we tested the interaction and time course of tDCS effects on force production when paired with a low-level force-matching task. Twenty-two subjects were randomized into two groups: tDCS-Matching and tDCS-Resting. Each group received tDCS and a sham stimulation, separated by one week. Maximal knee extensor and flexor torques were measured before and up to twenty-five minutes following the stimulation. The tDCS-Matching group produced greater knee extension torques relative to sham when compared with the tDCS-Resting group. There was no significant effect for knee flexion. This suggests that interference does not occur for force production tasks when tDCS is combined with a motor task. Rather, the task appears to aid and isolate the effects to the muscle groups involved in the task.
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Edward P
authors.initials: EP
authors.lastname: Washabaugh
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Michigan Medical School, Ann Arbor, MI, USA.
authors.forename: Luciana
authors.initials: L
authors.lastname: Santos
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Michigan Medical School, Ann Arbor, MI, USA.
authors.forename: Edward S
authors.initials: ES
authors.lastname: Claflin
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; School of Kinesiology, University of Michigan, Ann Arbor, MI, USA. Electronic address: mouli@umich.edu.
authors.forename: Chandramouli
authors.initials: C
authors.lastname: Krishnan
mesh_terms: D000704:Analysis of Variance; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007717:Knee / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D055070:Resistance Training; D013997:Time Factors; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
keywords: functional specificity; metaplasticity; muscle strength; noninvasive brain stimulation; transcranial magnetic stimulation; voluntary torque