Kobayashi A, Kikukawa A, Kimura M, Inui T, Miyamoto Y. Cerebral near-infrared spectroscopy to evaluate anti-G straining maneuvers in centrifuge training. Aviat Space Environ Med 2012; 83:790–4.Introduction: Over the past decade, near-infrared spectroscopy (NIRS) has emerged as an easily manageable noninvasive method for the continuous monitoring of cerebral cortical oxygenation during +G_z exposure. NIRS is also used to evaluate pilot trainees’ ability to adequately perform anti-G straining maneuvers in the course of centrifuge training. This study aimed to determine the general patterns and individual differences in NIRS recordings during +G_z exposure. Methods: There were 22 healthy male cadets who participated in the study. The centrifuge training profiles included a gradual onset run (GOR, onset rate of 0.1 G_z · s⁻¹) and short-term repeated exposures, with G_z levels from 4 to 7 G_z at an onset rate of 1.0 G_z · s⁻¹ (rapid onset run, ROR). Cortical tissue hemoglobin saturation (tissue oxygenation index, TOI) and changes in the concentration of oxygenated hemoglobin (O₂Hb) were recorded from the right forehead during the period of G_z exposure. Results: Most of the subjects successfully performed an anti-G straining maneuver and maintained or increased the cerebral oxygenation level during G_z exposure. In four subjects, however, oxygenation decline was observed at levels over 4 G_z, even though their anti-G systems were functioning. In contrast to the O₂Hb response, TOI, which reflects intracranial oxygenation changes, was decreased during the anti-G straining maneuver at G_z onset or during the countdown to a ROR exposure. Conclusion: Although NIRS is an effective tool for monitoring anti-G straining maneuver performance, it should be carefully evaluated in terms of intracranial oxygenation results.