Global physical activity remains low despite two decades of guideline updates, UTHealth Houston researchers find
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Andrea Ramirez Varela, MD, PhD, MPH, assistant professor in the Department of Epidemiology at UTHealth Houston School of Public Health.
view moreCredit: Photo by UTHealth Houston
The prevalence of physical activity among the global population has remained low for the last two decades despite a majority of countries making notable progress in developing policies that include physical activity, UTHealth Houston researchers found.
The study was published today in Nature Health and led by principal investigator Andrea Ramirez Varela, MD, PhD, MPH, assistant professor in the Department of Epidemiology at UTHealth Houston School of Public Health.
“Physical activity as a behavior that enhances health and has other benefits has really not increased since 2012,” said Ramirez Varela, who is also an assistant professor in the Department of Pediatrics at McGovern Medical School at UTHealth Houston. “But that can be mistakenly taken as if there was no action or policy action around it.”
According to Ramirez Varela’s research, 92% of countries have at least one policy document addressing physical activity. Of those countries, 35% have a policy specifically dedicated to physical activity.
While that’s a significant increase from the number of countries that had such policies in 2004, researchers found that 1 in 3 adults worldwide are still not meeting the World Health Organization physical activity guidelines. According to WHO, adults should get at least 150 minutes of moderate-intensity physical activity weekly.
Using a combination of information taken from interviews, peer-reviewed research, and policy documents from 218 countries between 2004 and 2025, Ramirez Varela and her team sought to propose solutions for how countries can translate physical activity guidelines into action.
“What we see in other modifiable risk factors for chronic diseases – like smoking, alcohol, nutrition – they have a lot of prioritization, and there is a lot of activity around putting them first. For physical activity, it has been different,” Ramirez Varela said. “We wanted to really understand why after all this apparent improvement in policy development, there was no change or the translation of this into the real world.”
Ramirez Varela’s team proposed that countries take a more proactive approach to defining and framing the issue of physical activity.
“There is no consensus if physical activity is an outcome or a means to achieve other outcomes,” Ramirez Varela said. “Do we want to increase physical activity levels to improve cardiovascular health and other outcomes, or do we want to just improve physical activity?”
Physical activity should also be framed as having both individual and population-level benefits, the team said.
“Physical activity should be embedded in the way we design our cities, helping create communities where people want to live and move more,” Ramirez Varela said. “It also belongs in education. Physical activity spans multiple sectors, yet the conversation has largely been focused on health.”
The research team also recommended that stakeholders build stronger leadership and partnership networks that promote physical activity.
“Almost thirty years ago, smoking was far less regulated. People were allowed to smoke on airplanes, indoors, and in most public spaces. Today, both tobacco industry and smoking behavior are subject to extensive regulations,” Ramirez Varela said. “We can build that same level of policy commitment for physical activity. The fact that it is not fully in place today simply means the work is ahead of us.”
The research was published in conjunction with two other population-level studies about physical activity, which Ramirez Varela co-authored.
Ramirez Varela’s work builds on more than two decades of research into physical activity that was first published in The Lancet in 2012. Subsequent studies into physical activity were also published in 2016 and 2021.
The late Harold W. Kohl III, PhD, professor of epidemiology at UTHealth Houston School of Public Health, also co-authored the paper.
Authors from The University of Sydney include Adrian Bauman, PhD; J. Jaime Miranda, MD; MSc, PhD; and Melody Ding, PhD, MPH.
Other authors include Catherine B. Woods, PhD, of the University of Limerick in Ireland; Yusra Ribhi Shawar, PhD, MPH; and Jeremy Shiffman, PhD, of Johns Hopkins University; Pedro C. Hallal, PhD, of the University of Illinois Urbana-Champaign; Deborah Salvo, PhD, of The University of Texas at Austin; Katja Siefken, PhD, of the Medical School Hamburg in Germany; Wanda Wendel-Vos, PhD, of the National Institute for Public Health and the Environment in the Netherlands; Juliana Mejia-Grueso, MSc, of the Global Observatory for Physical Activity; James F. Sallis, PhD, of the Australian Catholic University in Australia; Erica Hinckson, PhD, of the Auckland University of Technology in New Zealand; I-Min Lee, MBBS, MPH, ScD, of Harvard Medical School; Rodrigo Siqueira Reis, PhD, of Washington University in St. Louis, Missouri; Ulf Ekelund, PhD, of the Norwegian Public Health Institute; and Michael Pratt MD, MSPE, MPH, of the University of California San Diego.
Journal
Nature
Article Title
Low global physical activity despite two decades of policy progress
Article Publication Date
9-Mar-2026
Increasing fitness leads to bigger brain boost following exercise
University College London
Increasing our level of physical fitness leads to a bigger release of brain-boosting proteins following one session of exercise, a new study led by a UCL researcher has found.
The study, published in Brain Research, took a group of inactive unfit participants through a 12-week training programme of cycling three times per week and made them fitter. Researchers found as their fitness increased, so did the amount of brain-derived neurotrophic factor (BDNF) released following exercise, resulting in improved brain function.
Just 15 minutes of moderate to vigorous aerobic exercise releases BDNF, a brain protein which is known to support the formation of new neurons and new synapses (connections between brain cells), and maintains the health of existing neurons. This is the first study to show that for unfit people, just 12 weeks of consistent training can boost the brain’s response to a single 15-minute workout.
The study, led by Dr Flaminia Ronca (UCL Surgery & Interventional Science, and the Institute of Sport, Exercise and Health), involved 30 participants – 23 male and seven female – taking part in the 12-week programme. To assess fitness levels throughout the programme, participants completed VO2max tests every six weeks, which measures the maximum rate of oxygen your body can consume and use during intense exercise.
BDNF levels were measured pre- and post-VO2max testing, alongside a series of cognitive and memory tests, while also measuring changes in brain activity in the prefrontal cortex – where executive functions such as decision-making, emotion regulation, attention and impulsivity are controlled.
By the final week of the trial, results showed that baseline levels of BDNF did not change, but participants did show a larger spike of BDNF following intense exercise, compared to how their brains responded to intense exercise before the 12-week programme. This was linked to improvements in VO2max (aerobic fitness).
Higher overall BDNF levels and stronger exercise-induced increases were also associated with changes in activity across key areas of the prefrontal cortex during attention and inhibition tasks, though not during memory tasks.
Overall, the results showed that increasing physical fitness can enhance the brain’s ability to produce BDNF in response to acute bouts of exercise, which can have a strong positive influence on neural activity.
Lead author Dr Flaminia Ronca said: “We’ve known for a while that exercise is good for our brain, but the mechanisms through which this occurs are still being disentangled. The most exciting finding from our study is that if we become fitter, our brains benefit even more from a single session of exercise, and this can change in only six weeks.”
Notes to editors:
For more information or to speak to the researchers involved, please contact: Tom Cramp, UCL Media Relations , T: +447586 711698, E: t.cramp@ucl.ac.uk
The research paper: 'BDNF relates to prefrontal cortex activity in the context of physical exercise', Flaminia Ronca, Cian Xu, Ellen Kong, Dennis Chan, Antonia Hamilton, Giampietro Schiavo, Ilias Tachtsidis, Paola Pinti, Benjamin Tari, Tom Gurney, Paul W. Burgess, is published in Brain Research, March 2026, https://doi.org/10.1016/j.brainres.2026.150253
About UCL (University College London)
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Since 1826, we have championed independent thought by attracting and nurturing the world's best minds. Our community of more than 50,000 students from 150 countries and over 16,000 staff pursues academic excellence, breaks boundaries and makes a positive impact on real world problems.
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Journal
Brain Research
Method of Research
Experimental study
Subject of Research
People
Article Title
BDNF relates to prefrontal cortex activity in the context of physical exercise
Article Publication Date
4-Mar-2026
Exercise triggers memory-related brain 'ripples' in humans, researchers report
University of Iowa-led study captures how a single bout of exercise activates neural rhythms tied to learning and recall
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An University of Iowa-led research team has documented in humans that physical exercise sparks an increase in brain waves called ripples connecting areas in the brain linked to learning and memory. The researchers noted that a single exercise session spawns a spike in ripples and learning-memory connections.
view moreCredit: Tim Schoon, University of Iowa
A single session of physical exercise can spawn a boost of neural activity in brain networks that underlie learning and memory, according to a new study led by the University of Iowa.
The researchers measured neural activity in the brains of patients with epilepsy before and after they completed a bout of physical exercise. The results showed that a single exercise session produced in the participants a burst of high-frequency brain waves, called ripples, emanating from the hippocampus to areas of the brain involved in learning and recall.
Neuroscientists have documented ripples relevant to memory in mice and rats, but they had not confirmed the link in humans, mainly because electrodes need to be implanted in the brain to obtain recordings. Instead, researchers had theorized the ripples’ role in humans, based on studies in people that measured changes in oxygenated blood in the brain after exercise. This new study marks the first time researchers have been able to see the neurons in action in people following exercise, the authors report.
The Iowa-led team recruited 14 patients at University of Iowa Health Care Medical Center, between 17 and 50 years of age, to participate. After a brief warmup, participants rode a stationary bike for 20 minutes at a pace they could maintain for the duration. Researchers recorded the participants’ brain activity before and after the cycling session using intracranial electroencephalography (iEEG), which utilizes implanted electrodes to measure neural activity in the brain.
The recordings showed an increased rate of ripples originating in the hippocampus and connecting with cortical regions of the brain known to be involved in learning and memory performance.
"We’ve known for years that physical exercise is often good for cognitive functions like memory, and this benefit is associated with changes in brain health, largely from behavioral studies and noninvasive brain imaging,” says Michelle Voss, professor and Ronnie Ketchel Faculty Fellow in the Department of Psychological and Brain Sciences at Iowa and the study’s corresponding author. “By directly recording brain activity, our study shows, for the first time in humans, that even a single bout of exercise can rapidly alter the neural rhythms and brain networks involved in memory and cognitive function."
Voss says the results apply beyond the epileptic patients who participated.
“The patterns we see after exercise closely match what’s been observed in healthy adults using noninvasive brain imaging, like fMRI. That convergence across very different methods is one of the strongest indicators that the effects are not specific to epilepsy but reflect a more general human brain response to exercise,” she says.
The researchers plan to seek funding to cement the exercise-memory link in the brain by having participants take memory tests after an exercise session as their brain activity is being directly recorded.
The study, “Exercise enhances hippocampal-cortical ripple interactions in the human brain,” was published online on March 9 in the journal Brain Communications, part of Oxford Academic.
Co-lead authors are Araceli Cardenas, from Toronto Western Hospital, who was a postdoctoral researcher in neurosurgery at Iowa; and Juan Ramirez-Villegas, from the Institute of Science and Technology in Austria.
Study co-authors from Iowa are Christopher Kovach, Phillip Gander, Rachel Cole, Hiroto Kawasaki, Jeremy Greenlee, Matthew Howard, and Kirill Nourski.
Other contributing authors are Andrew Grossbach from Ohio State University and Matthew Banks from the University of Wisconsin-Madison.
The research was funded through the University of Iowa.
Journal
Brain Communications
Method of Research
Observational study
Subject of Research
People
Article Title
Exercise enhances hippocampal-cortical ripple interactions in the human brain
Article Publication Date
9-Mar-2026
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