Strenuous Exercise Alters Brain Creatine and Glutamate/Glutamine (Glx) in Humans: Evidence From Dynamic 1H-MRS and 1H-MRSI.

The acute effects of exercise on brain energy metabolism are poorly understood. We used dynamic proton magnetic resonance spectroscopy (1H-MRS) to quantify responses of total creatine (tCr), glutamate/glutamine (Glx), and lactate across brain regions following a single bout of strenuous exercise. Sixteen healthy adults (nine female, age: 25 ± 3 years) completed ~15 min of cycling, reaching ~85% of predicted heart rate maximum. Single-voxel 1H-MRS was acquired at 3 Tesla from frontal and visual cortices before (PRE), 15- (POST15), and 30-min (POST30) following exercise. Multivoxel 1H-MRSI was acquired from frontal and parietal regions PRE and 25-min following exercise (POST25). tCr concentrations decreased by 5.9% in the frontal cortex between PRE and POST15 (6.87 vs. 6.47 mmol·L-1; p < 0.001) and remained significantly lower than PRE at POST30 (6.87 vs. 6.66 mmol·L-1; p = 0.030). Glx concentrations increased by 28.9% in the frontal cortex between PRE and POST15 (6.82 vs. 8.79 mmol·L-1; p = 0.002), returning to baseline by POST30 (p = 0.890). In exploratory analyses (n = 5 after quality control), lactate concentrations increased by 76% in the frontal cortex between PRE and POST15 (0.45 vs. 0.79 mmol·L-1) and remained elevated by 46% at POST30 compared to PRE (0.45 vs. 0.65 mmol·L-1). tCr resonance signals were 5.1% lower across the MRSI grid at POST25 compared with PRE (792.4 vs. 835.4 a.u.; p = 0.001), whereas Glx signals were 11.4% higher at POST25 (1349.8 vs. 1211.4 a.u.; p = 0.003), although region-specific responses were shown. These findings suggest that creatine (Cr) and lactate may serve as alternative energy substrates in response to vigorous exercise, and support Glx as an indicator of excitatory neurotransmission that responds to exercise.