Brain blood flow during exercise: towards a more complete picture

Regional brain blood flow increases up to moderate intensity exercise.  At higher exercise intensities, blood flow velocity in the middle cerebral artery levels off (at around 50-60% of maximal exercise) and then decreases during heavy exercise. This blood flow pattern has also been observed in the internal carotid artery. Potential mechanisms underlying such a response include a reduction in partial pressure of arterial carbon dioxide (PaCO2) induced by hyperventilation or high exercise-induced sympathetic nerve activation. Interestingly, vertebral artery blood flow and common carotid artery blood flow increase from rest to heavy exercise.

In a study recently published in the Journal of Physiology, Sato et al. examined the relative contribution of different cerebral arteries (common carotid artery, internal carotid artery, external carotid artery, vertebral artery and middle cerebral artery) providing blood flow to the brain and head during two incremental cycle exercises (the incremental exercise protocol needed to be performed twice in order to have the complete picture due to insufficient space at the level of the neck and interference between Doppler beams from multiple probes) in healthy subject. The figure below shows blood flow responses in each artery at different exercise intensities.

As in several other studies, these authors observed transient elevations in blood flow velocity in the middle cerebral artery and blood flow in the internal carotid artery from rest to 60% of maximal exercise followed by a reduction in blood flow at 80% of maximal exercise. However, blood flow in the common carotid artery, external carotid artery and vertebral artery increased from rest to heavy exercise.

Interestingly, the elevation in external carotid artery blood flow from moderate- to high-intensity exercise was negatively correlated with the decrease in internal carotid artery blood flow. The latter suggests that a large elevation in external carotid artery blood flow may contribute to the decrease in internal carotid artery blood flow observed during heavy exercise. In other words, although we already know that PaCO2 is a primary contributor in the regulation of brain blood flow during exercise, this study suggests that the distribution of carotid blood flow could limit the elevation in internal carotid blood flow during heavy aerobic exercise.

Reference

Sato, K., Ogoh, S., Hirasawa, A., Oue, A., & Sadamoto, T. (2011). The distribution of blood flow in the carotid and vertebral arteries during dynamic exercise in humans. The Journal of physiology, 589(Pt 11), 2847–2856. doi:10.1113/jphysiol.2010.204461

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14 thoughts on “Brain blood flow during exercise: towards a more complete picture

  1. Great blog and great summary… trying to get the paper myself now and will be interested to read it in full. Only stumbled across it from your twitter and this blog so thanks for directing me! BW, Chris

    1. Thanks for the good words Chris! Let me know if you are not able to get the paper, I will send it to you. The paper is very interesting. I have only presented changes in brain blood flow in this post but there is a lot more in the paper !

      1. I’ve emailed Dr. Sato about the paper (and also emailed the authors of another in that volume: “Cool head, hot brain: cerebral blood flow distribution during exercise”) because I am having JPhys access problems but would be most grateful if you could send over a copy. I am currently looking at CBF for a grant application and so would love a read and then perhaps I’ll have a few questions for you too!

  2. With the blood flow through the brain, can this stimulate hair growth? Also, while exercising, can I increase the blood flow by massaging the sice of my head? This massaging of my head also reduces the skin tightness. It is my understanding that one of the factor in hair loss is the tight scalp which prevents blood to the hair particles.

    1. Good point. Correlation does not imply causation. Further research is definitely needed to investigate if the distribution of carotid blood flow (by manipulation of external carotid artery blood flow for example) influences the changes in internal carotid blood flow during heavy exercise.

      1. About two years ago, I was bald at the top of my head (about 10 noticeable strands of hair)with a tight scalp. For three months, each day I would massage my scalp for 15 minutes and I began to notice some hair growth, not much. I did it in my car while I stopped for the light to change; Imassaged my scalp while watching television and movies. After six months, I noticed more strands of hair. Still not much. Then, for exercise, I would walk around a track. I decided and was brave enough to my massage my scalp while walking. I would massage my scalp between 15 to 30 minutes each day. About three months later, I noticed more strands of hair.

        I attributed my hair growth (my original hair loss occurred over 15 years) to exercising while massaging my scalp to loosening my scalp (not as tight as before) and having more blood flow. Be nice if more men would do this. It is free to do and I also read that raising the blood level to your brain (from intense exercising) creates more neurons and also less chance of a stroke.

    1. What’s really interesting is that you’re doing it anyway, walking, watching television, driving, and you might as well be massaging your scalp. Also, I find myself not rushing through the yellow lights but relaxing and massaging my scalp.

      Also, it’s free and if you don’t mind people staring at you, it stops (atleast slows it down) hair loss and if you have patience and determination, it does work.

    1. Are you referring to the elevation in ICA blood flow\MCA blood flow velocity during exercise ? It might well be (at least in part)!

      For example, a transient occlusion of cerebral blood flow in patients with cerebrovascular disease impairs cognition until the occlusion is removed.

      Investigators have also reported that cognitive performance of athletes (measured by the Stroop test) is enhanced during exercise.

      A recent study (Lucas et al. Experimental Gerontology In press) suggested that regardless of age, cognition is improved while exercising compared to the resting state.

      In regards to mental health, a reduction in cerebral blood flow has been associated with depression for example…

      So, evidence suggests that changes in cerebral blood flow during exercise could have a positive impact on mental health and performance. However, changes in other variables during exercise (such as brain-derived neurotrophic factor) may also contribute to improvements in mental health/performance.

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