Figure 1.

(A) Study design. Subjects were administered creatine at 8:30 p.m. in one session and placebo in another, spaced at least five days in random order. Seven participants completed the verum and eight the placebo as the first condition. Cognitive and metabolic parameters were acquired in four runs, baseline starting at 6 p.m., the other at 0 a.m., 2 a.m., and 4 a.m. Each session took 1 h:35 min and comprised two ³¹P-MRS-, three ¹H-MRS measurements, followed by fatigue scores, psychomotor vigilance tests (PVT), and other cognitive tasks (Cog.Test). (B) Positioning of three single voxel ¹H-MR-spectroscopy (PRESS) voxels (left, red) and two 8 × 8 ³¹P-MRS CSI grids (right, white) in coronal, transversal and sagittal view. Isotropic voxel size was (25 mm)³ except for the frontal PRESS-voxel of double volume. Exemplary spectra are given with some signals assigned. Signals exploited in this study were of ³¹P-MRS Pi at ≈5 ppm, PCr set at 0 ppm and the ATP-β-signal at − 16.3 ppm, of ¹H-MRS the CH₃-signal at 3.2 ppm, and the CH₂-signal at 3.92 ppm of creatine (total creatine, tCr), N-acetyl-aspartate (NAA) at 2.0 ppm and signals of glutamate (Glu) at 2.35 (C3, C4-protons) and glutamine or glutamate (Glx) at 3.75 ppm (C2-proton).