Enhancing effect of cerebral blood volume by mild exercise in healthy young men: A near-infrared spectroscopy study Akkaranee Timinkul a , Morimasa Kato e , Takenori Omori a , Custer C. Deocaris a , Akira Ito a , Tomohiro Kizuka b , Yosuke Sakairi c , Takeshi Nishijima a , Takashi Asada d , Hideaki Soya a, * a Laboratory of Exercise Biochemistry, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8574, Japan b Kinesiology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8574, Japan c Sports Psychology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8574, Japan d Department of Psychiatry, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8575, Japan e Junior College of Yamagata Prefecture, Yonezawa, Japan Received 5 October 2007; accepted 17 March 2008 Available online 9 April 2008 Abstract A mechanism by which exercise improves brain function may be attributed to increase in cerebral blood volume (CBV) with physical activity. However, the exact exercise intensity that influences CBV is still uncertain. To clarify this issue, 10 healthy young male participants were asked to perform a graded cycling exercise to the point of exhaustion while their prefrontal cortex CBVs are being monitored using near-infrared spectroscopy. Overall responsive cerebral oxygenation showed a non-linear pattern with three distinct phases. The CBV-threshold (CBVT), an event where rapid oxygenation takes place, occurred at approximately 42% of the ˙ VO 2 max. The CBVT preceded the lactate threshold (LT), which was at approximately 55% of the ˙ VO 2 max. The ˙ VO 2 max was not predictive of the CBVT in among the subjects. Our results indicate that oxygenation of the prefrontal cortex increases during graded cycling even at exercise intensities below the LT, suggesting the potential role of mild exercise in enhancing CBV. # 2008 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. Keywords: Near-infrared spectroscopy; Cerebral oxygenation; Prefrontal cortex; Lactate threshold; Graded cycling exercise 1. Introduction Exercise has an important role not only in promoting general health but also in the prevention and treatment of various kinds of ailments, such as mood disorders (Agras, 1995) and constitutional hypotension (Duschek and Schandry, 2007). It is suggested that exercise would improve brain functions by increasing cerebral blood volume (CBV), however, the exact mechanisms are still unknown. In recent years, advances in neuroimaging techniques have made it is possible to investigate changes in the brain. It brought more understanding about cerebral activation processes, due to the close coupling of neural activity and brain metabolism, that accompany changes in cerebral blood flow (Kuschinsky, 1991; Burke and Bu ¨hrle, 2006). In addition, the evidence that hypoperfusion was delimited to the left dorsolateral prefrontal cortex (Brodmann areas 9, 10, 45, and 46) and the anterior cingulate cortex in mood disorders participants (Videbech, 2000). The increase in brain perfusion was found associated with improved symptoms through various methods (e.g. anti-depressant, electroconvul- sive therapy, exercise) (Vasile et al., 1997; Navarro et al., 2004). These findings have drawn much attention to the effects of exercise by restoring reduced cerebral blood volume. Duschek and Schandry (2007) reported recently that impaired brain perfusion in hypotension especially in middle cerebral arteries (MCA) can cause cognitive deficits and even depression. Interestingly, cognitive performance may also be enhanced by pharmacological blood pressure elevation. Regarding their crucial importance in the cognitive processes, the prefrontal and anterior cingulate cortices have been given much consideration to study. Exercise has been recommended for the prescription but the exact intensity of physical activity is still unclear (Duschek and Schandry, 2007). Until now, reports on how cerebral blood www.elsevier.com/locate/neures Available online at www.sciencedirect.com Neuroscience Research 61 (2008) 242–248 * Corresponding author. Tel.: +81 29 853 2620; fax: +81 29 853 2620. E-mail address: hsoya@taiiku.tsukuba.ac.jp (H. Soya). 0168-0102/$ – see front matter # 2008 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. doi:10.1016/j.neures.2008.03.012