Concomitant dual-site tDCS and dark chocolate improve cognitive and endurance performance following cognitive effort under hypoxia: a randomized controlled trial

Figures

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  Figure 1. Reaction time changes in the four experimental conditions. Comparison of choice reaction time performance (A) at baseline in normoxia and after performing a modified Stroop task (incongruent only) for 30 min in hypoxia among experimental conditions. Choice reaction time performance (B) before, during, and immediately after the time to exhaustion test (TTE) under hypoxia (O2 = 13%) after performing an incongruent-only Stroop task for 30 min and receiving anodal or sham Transcranial Direct Current Stimulation for 20 min in hypoxia. * = “DC + a-tDCS" significantly higher than “WC + sh-tDCS” (p = 0.003). DC dark chocolate; WC white chocolate; a-tDCS anodal transcranial direct current stimulation; sh-tDCS sham transcranial direct current stimulation.

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  Figure 2. Endurance performance and physiological responses in the four experimental conditions. Time to exhaustion test (A), heart rate (B), blood oxygen saturation (SpO2; C), and electromyographic (EMG) amplitude of the vastus lateralis (D), vastus medialis (E), and rectus femoris (F) during the endurance cycling task under four experimental conditions in hypoxia. * = significantly different from WC + sh-tDCS (p < 0.05); # = significantly different from WC + a-tDCS (p < 0.05). DC dark chocolate; WC white chocolate; a-tDCS anodal transcranial direct current stimulation; sh-tDCS sham transcranial direct current stimulation.

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  Figure 3. Psychophysiological responses to exercise in the four experimental conditions. Ratings of perceived exertion (RPE; A), affective responses (B), and felt arousal (C) during the endurance cycling task under four experimental conditions in hypoxia. DC dark chocolate; WC white chocolate; a-tDCS anodal transcranial direct current stimulation; sh-tDCS sham transcranial direct current stimulation.

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  Figure 4. Study flowchart. PPO Peak Power Output; CRT Choice Reaction Time; tDCS Transcranial Direct Current Stimulation; TTE Time to Exhaustion; HR Heart Rate; SpO2 Blood Oxygen Saturation; RPE Rating of Perceived Exertion; EMG Electromyography; PS Pleasure Sensation (i.e., affective responses); FA Felt Arousal.

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  Figure 5. Strength and radial component of the electric field induced by tDCS. Finite Element Models derived from Magnetic Resonance Imaging in a head model (MNI152) of the strength and radial (normal to the cortical surface) component of the electric field (EF) induced by tDCS. Electrode montage targeting the simultaneous stimulation with anodal tDCS of the representation of the lower limbs in the primary motor cortex and the left dorsolateral prefrontal cortex (A, B), with red electrodes representing the anodes (5 × 4 cm) and blue electrodes representing the cathodes (9 × 4 cm). The EF strength is presented in the color-coded figures (C–F), with hotter colors indicating stronger EF and colder colors indicating the opposite. The radial EF is presented in the color-coded figures (G–J), where red color represents the electric current flowing into the cortex (i.e., inducing excitatory effects) and blue color represents the electric current flowing out of the cortex (i.e., inducing inhibitory effects). The study montage has reached the target areas with enough electric current strength to induce a neuromodulatory effect, as shown in figures (E) and (F) (blue circles roughly representing the…