Effects Of Transcranial Direct Current Stimulation On Physical Activity In Healthy Subjects: A Pilot Study

Abstract

Physical activity (PA) has well-established health benefits. Current efforts to enhance PA have targeted mainly socio-economic factors. Despite these efforts, only a small number of adults engages in regular PA. Regulation of voluntary PA is linked to brain mechanisms involving the dopaminergic system. Transcranial direct current stimulation (tDCS) involves neuromodulation and can target specifically the dopaminergic system. PURPOSE: To determine if tDCS targeted to the left dorsolateral prefrontal cortex and coupled to an exercise stimulus increases overall daily PA in healthy subjects. METHODS: In a single-blinded parallel design, subjects were randomly assigned to a group undergoing Active (n = 13) (mean ± SD; age = 26.8 ± 10.2 years; 3 males, 10 females) or Sham/control (n = 9) (age = 23.3 ± 7.9 years; 2 males, 7 females) tDCS. PA was monitored using a thigh-worn activPAL micro accelerometer for 2 weeks before (PRE) and 3 weeks during (DUR) the tDCS intervention. The tDCS intervention consisted of 20 mins of tDCS (ie. active or sham), followed by brisk walking for 30 mins, 3 times a week during DUR. PA was evaluated as Total Daily Steps (TDS) and Activity Score (AS; describing PA energy expenditure in terms of metabolic equivalent (MET)). Collected data corresponding to PRE and DUR were averaged for the course of week 2 and 3, respectively. Informed consent was obtained at the time of enrollment and the research was approved by the ASU Institutional Review Board. RESULTS: ANOVA analyses found significant effects for time for TDS (P < 0.001), but not for AS (P > 0.05). Pairwise comparisons indicated no significant effects for neither TDS or AS at PRE. TDS (steps) increased in response to the tDCS, in both the Active (DUR, 7411 ± 2126 vs PRE, 6201 ± 2303; P < 0.01) and the Sham (DUR, 6840 ± 1443 vs PRE, 5778 ± 1508; P < 0.05) groups. However, TDS response was ~14% higher in the Active Group. AS (MET-hr/day) increased in response to the tDCS in the Active (DUR, 33.2 ± 0.9 vs PRE, 32.8 ± 0.9 steps; P ≤ 0.05), but not Sham (DUR, 32.8 ± 0.8 vs PRE, 32.8 ± 0.6 steps; P > 0.05) group. CONCLUSION: Three weeks of active tDCS increases measures of daily PA in healthy subjects. Although studies with larger number of subjects are needed, this study provides preliminary evidence for neurostimulation as a promising intervention to increase PA in healthy adults.