Summary: Researchers report a measurable decline in cerebral blood flow after physically fit older adults paused their exercise for a short period.
Source: University of Maryland.
Stopping regular endurance exercise for just ten days led to a significant reduction in blood flow to multiple brain regions, including the hippocampus, in healthy, physically fit older adults, according to a study led by researchers at the University of Maryland School of Public Health. Using MRI perfusion imaging, the team compared cerebral blood flow at peak training and again after a 10-day cessation of all exercise and vigorous activity, finding notable decreases in regions important for memory and cognition.
“The hippocampus is central to learning and memory and is one of the earliest regions affected in Alzheimer’s disease,” says Dr. J. Carson Smith, associate professor of kinesiology and lead author of the study, published in Frontiers in Aging Neuroscience in August 2016. “Animal studies show that exercise promotes new blood vessel growth and neurogenesis in the hippocampus, and in older humans, regular exercise helps preserve hippocampal volume. That makes the observed drop in hippocampal blood flow after only 10 days without exercise particularly important for understanding how quickly cerebrovascular and brain health can respond to changes in activity.”
The study recruited 12 “master athletes,” defined as adults aged 50 to 80 with at least 15 years of sustained endurance training and recent participation in endurance events. On average the participants were 61 years old and reported training volumes comparable to about a 10K run per day (approximately 36 miles or 59 km per week). Their aerobic capacity (VO2 max) was in the top 10 percent for their age group, reflecting sustained high-level fitness.
Researchers measured resting cerebral blood flow (rCBF) with perfusion-weighted MRI while participants were at peak fitness and immediately after 10 consecutive days in which they refrained from all training and vigorous activity. Voxel-wise analysis across gray matter and a targeted region-of-interest analysis in the hippocampus showed statistically significant rCBF decreases in eight gray matter regions and in both the left and right hippocampus.
The gray matter regions showing reduced blood flow included the left inferior temporal gyrus, left fusiform gyrus, left inferior parietal lobule, right cerebellar tonsil, right lingual gyrus, right precuneus, and bilateral cerebellar areas. Several of these areas are components of the brain’s default mode network, which is known to be vulnerable in aging and in Alzheimer’s disease. Although the study did not detect a measurable decline in cognitive test performance after 10 days of no exercise, the vascular changes it documented are consistent with the broader evidence linking lower physical activity to a higher risk of cognitive decline and dementia over time.
“Our primary finding is that resting cerebral blood flow, including hippocampal blood flow, is sensitive to short-term reductions in exercise among highly trained older adults,” Dr. Smith notes. “This suggests the cerebrovascular system adapts rapidly to changes in physical activity. The clinical implications remain to be defined: we need studies to determine how quickly these changes occur, how long they persist, whether longer breaks produce greater or lasting effects, and how rapidly normal blood flow is restored once training resumes.”
Funding: The study was supported by a grant from the National Institutes of Health (HL098810). The contents are the authors’ responsibility and do not necessarily represent the official views of the NIH.
Source: Kelly Blake – University of Maryland.
Image Source: This NeuroscienceNews.com image is in the public domain.
Original Research: The open-access study is titled “Hippocampal and Cerebral Blood Flow after Exercise Cessation in Master Athletes” by Alfonso J. Alfini, Lauren R. Weiss, Brooks P. Leitner, Theresa J. Smith, James M. Hagberg and J. Carson Smith in Frontiers in Aging Neuroscience, published online August 5, 2016.
Suggested citations: University of Maryland. “Stopping Exercise Decreases Brain Blood Flow.” Neuroscience News. (2016). MLA, APA, and Chicago citation formats are commonly used; please adapt to your preferred style.
Abstract (revised summary)
Hippocampal and Cerebral Blood Flow after Exercise Cessation in Master Athletes
Endurance exercise training benefits cerebrovascular health and exerts neurotrophic effects in the hippocampus, but the effects of stopping regular training are not well understood. This study measured the effect of a 10-day cessation of endurance training on resting cerebral blood flow in healthy, highly trained older adults. Twelve master athletes (age ≥ 50 years) with long-term endurance training histories (≥ 15 years) ceased all training for 10 consecutive days. Perfusion-weighted MRI measured rCBF before and immediately after the detraining period. Voxel-wise analysis in gray matter and region-of-interest analysis in the hippocampus identified significant decreases in rCBF across eight gray matter regions and in both hippocampi following the 10-day break. These results indicate that resting hippocampal and cortical blood flow respond quickly to short-term reductions in exercise training among master athletes, suggesting that transient exercise cessation can serve as a model to investigate how acute changes in physical activity influence brain vascular function in older adults.