Physical activity may have a stronger role than genes in longevity

Previous research has shown that low physical activity and greater time spent sitting are associated with a higher risk of death. Does risk change if a person is genetically predisposed to live a long life?

That is the question researchers at the Herbert Wertheim School of Public Health and Human Longevity Science at University of California San Diego set out to answer in a study published in the August 24, 2022 online edition of the Journal of Aging and Physical Activity.

“The goal of this research was to understand whether associations between physical activity and sedentary time with death varied based on different levels of genetic predisposition for longevity,” said lead author Alexander Posis, M.P.H., a fourth-year doctoral student in the San Diego State University/UC San Diego Joint Doctoral Program in Public Health.

In 2012, as part of the Women’s Health Initiative Objective Physical Activity and Cardiovascular Health study (OPACH), researchers began measuring the physical activity of 5,446 women in the United States who were 63 and older, following them through 2020 to determine mortality. Participants wore a research-grade accelerometer for up to seven days to measure how much time they spent moving, the intensity of physical activity, and sedentary time.

The prospective study found that higher levels of light physical activity and moderate-to-vigorous physical activity were associated with lower risk of death. Higher sedentary time was associated with higher risk of mortality. These associations were consistent among women who had different levels of genetic predisposition for longevity.

"Our study showed that, even if you aren't likely to live long based on your genes, you can still extend your lifespan by engaging in positive lifestyle behaviors such as regular exercise and sitting less," said senior author Aladdin H. Shadyab, Ph.D., assistant professor at the Herbert Wertheim School of Public Health and Human Longevity Science at UC San Diego. “Conversely, even if your genes predispose you to a long life, remaining physically active is still important to achieve longevity.”

Given the aging adult population in the United States, and longer time spent engaging in lower intensity activities, the study findings support recommendations that older women should participate in physical activity of any intensity to reduce the risk of disease and premature death, wrote the authors.

JOURNAL

Journal of Aging and Physical Activity

DOI

10.1123/japa.2022-0067 

What older adults do while they sit affects dementia risk

 

Adults aged 60 and older who sit for long periods watching TV or other such passive, sedentary behaviors may be at increased risk of developing dementia, according to a new study by USC and University of Arizona researchers.

Their study also showed that the risk is lower for those who are active while sitting, such as when they read or use computers.

The study was published today in the journal Proceedings of the National Academy of Sciences. It also revealed that the link between sedentary behavior and dementia risk persisted even among participants who were physically active.

“It isn’t the time spent sitting, per se, but the type of sedentary activity performed during leisure time that impacts dementia risk,” said study author David Raichlen, professor of biological sciences and anthropology at the USC Dornsife College of Letters, Arts and Sciences.

“We know from past studies that watching TV involves low levels of muscle activity and energy use compared with using a computer or reading," he said. "And while research has shown that uninterrupted sitting for long periods is linked with reduced blood flow in the brain, the relatively greater intellectual stimulation that occurs during computer use may counteract the negative effects of sitting.”

Researchers used self-reported data from the U.K. Biobank, a large-scale biomedical database of more than 500,000 participants across the United Kingdom, to investigate possible correlations between sedentary leisure activity and dementia in older adults.

More than 145,000 participants aged 60 and older — all of whom did not have a diagnosis of dementia at the start of the project — used touchscreen questionnaires to self-report information about their levels of sedentary behavior during the 2006-2010 baseline examination period.

After an average of nearly 12 years of follow-up, the researchers used hospital inpatient records to determine dementia diagnosis. They found 3,507 positive cases.

Then, the team adjusted for certain demographics (e.g., age, sex, race/ethnicity, employment type) and lifestyle characteristics (e.g., exercise, smoking and alcohol use, time spent sleeping and engaging in social contact) that could affect brain health.

The impact of physical activity, mental activity on risk

The results remained the same even after the scientists accounted for levels of physical activity. Even in individuals who are highly physically active, time spent watching TV was associated with increased risk of dementia, and leisure-time spent using a computer was associated with a reduced risk of developing dementia.

“Although we know that physical activity is good for our brain health, many of us think that if we are just more physically active during the day, we can counter the negative effects of time spent sitting,” said study author Gene Alexander, professor of Psychology and Evelyn F. McKnight Brain Institute at the University of Arizona.

“Our findings suggest that the brain impacts of sitting during our leisure activities are really separate from how physically active we are,” said Alexander, “and that being more mentally active, like when using computers, may be a key way to help counter the increased risk of dementia related to more passive sedentary behaviors, like watching TV.”

Knowing how sedentary activities impact human health could lead to some improvements.

“What we do while we’re sitting matters, " Raichlen added. "This knowledge is critical when it comes to designing targeted public health interventions aimed at reducing the risk of neurodegenerative disease from sedentary activities through positive behavior change.”

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In addition to Raichlen and Alexander, other authors of the study include M. Katherine Sayre, Mark H.C. Lai, and Rand R. Wilcox of USC; and Yann C. Klimentidis, and Pradyumna K. Bharadwaj of the University of Arizona.

The study was supported by grants from the National Institutes of Health (P30AG072980, P30AG019610, R56AG067200, R01AG049464, R01AG72445), the state of Arizona and Arizona Department of Health Services, and the McKnight Brain Research Foundation.

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JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2206931119 

Regular physical activity linked to lower risk of COVID-19 infection and severity

Regular physical activity is linked to a lower risk of COVID-19 infection and severity, including hospital admission and death, finds a pooled data analysis of the available evidence, published online in the British Journal of Sports Medicine.

A weekly tally of 150 minutes of moderate intensity, or 75 minutes of vigorous intensity, physical activity seems to afford the best protection, the analysis suggests.

Previous research suggests that physical activity can lessen both the risk of infection and the severity of respiratory infections due, at least in part, to its ability to bolster the immune system.

The link between regular physical activity and COVID-19 severity is poorly understood, but probably involves both metabolic and environmental factors, say the researchers, who set out to try and quantify the threshold of physical activity that might be needed to lessen the risks of infection and associated hospital admission and death.

They searched 3 major research databases for relevant studies published between November 2019 and March 2022, and from an initial haul of 291, pooled the results of 16. 

The studies included a total of 1,853,610 adults, just over half of whom (54%) were women. The average age of participants was 53.

Most of the studies were observational and were carried out in South Korea, England, Iran, Canada, the UK, Spain, Brazil, Palestine, South Africa and Sweden. 

The pooled data analysis showed that, overall, those who included regular physical activity in their weekly routine had an 11% lower risk of infection with SARS-CoV-2, the virus responsible for COVID-19.

They also had a 36% lower risk of hospital admission, a 44% lower risk of severe COVID-19 illness, and a 43% lower risk of death from COVID-19 than their physically inactive peers. 

The maximum protective effect occurred at around 500 Metabolic Equivalent of Task (MET) minutes a week, after which there were no further improvements.

METS express the amount of energy (calories) expended per minute of physical activity, and 500 of them are the equivalent of 150 minutes of moderate intensity, or 75 minutes of vigorous intensity, physical activity.

The researchers caution that the analysis included observational studies, differing study designs, subjective assessments of physical activity levels, and concerned only the Beta and Delta variants of SARS-CoV-2 rather than Omicron, all of which may weaken the findings.

But there are plausible biological explanations for what they found, they say. Regular moderate-intensity exercise may help to boost the body’s anti-inflammatory responses, as well as cardiorespiratory and muscular fitness, all of which may explain its beneficial effects on COVID-19 severity, they suggest.

They conclude: “Our findings highlight the protective effects of engaging in sufficient physical activity as a public health strategy, with potential benefits to reduce the risk of severe COVID-19. 

“Given the heterogeneity and risk of publication bias, further studies with standardised methodology and outcome reporting are now needed.”

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Lack of sleep makes us less generous

 Humans help each other — it’s one of the foundations of civilized society. But a new study by scientists at the University of California, Berkeley, reveals that a lack of sleep blunts this fundamental human attribute, with real-world consequences.

Lack of sleep is known to be associated with an increased risk of cardiovascular disease, depression, diabetes, hypertension and overall mortality. However, these new discoveries show that a lack of sleep also impairs our basic social conscience, making us withdraw our desire and willingness to help other people.

In one portion of the new study, the scientists showed that charitable giving in the week after the beginning of Daylight Saving Time, when residents of most states “spring forward” and lose one hour of their day, dropped by 10% — a decrease not seen in states that do not change their clocks or when states return to standard time in the fall.

The study, led by UC Berkeley research scientist Eti Ben Simon and Matthew Walker, a UC Berkeley professor of psychology, adds to a growing body of evidence demonstrating that inadequate sleep not only harms the mental and physical well-being of an individual, but also compromises the bonds between individuals — and even the altruistic sentiment of an entire nation.

“Over the past 20 years, we have discovered a very intimate link between our sleep health and our mental health. Indeed, we've not been able to discover a single major psychiatric condition in which sleep is normal,” Walker said. “But this new work demonstrates that a lack of sleep not only damages the health of an individual, but degrades social interactions between individuals and, furthermore, degrades the very fabric of human society itself. How we operate as a social species — and we are a social species — seems profoundly dependent on how much sleep we are getting.”

“We're starting to see more and more studies, including this one, where the effects of sleep loss don't just stop at the individual, but propagate to those around us,” said Ben Simon. “If you're not getting enough sleep, it doesn't just hurt your own well-being, it hurts the well-being of your entire social circle, including strangers.”

Ben Simon, Walker and colleagues Raphael Vallat and Aubrey Rossi will publish their results August 23 in the open access journal PLOS Biology. Walker is the director of the Center for Human Sleep Science. He and Ben Simon are members of the Helen Wills Neuroscience Institute at UC Berkeley.

Sleeplessness dampens theory of mind network

The new report describes three separate studies that assessed the impact of sleep loss on people’s willingness to help others. In the first study, the scientists placed 24 healthy volunteers in a functional magnetic resonance imager (fMRI) to scan their brains after eight hours of sleep and after a night of no sleep. They found that areas of the brain that form the theory of mind network, which is engaged when people empathize with others or try to understand other people’s wants and needs, were less active after a sleepless night.

“When we think about other people, this network engages and allows us to comprehend what other person’s needs are: What are they thinking about? Are they in pain? Do they need help?” Ben Simon said. “However, this network was markedly impaired when individuals were sleep deprived. It’s as though these parts of the brain fail to respond when we are trying to interact with other people after not getting enough sleep.”

In a second study, they tracked more than 100 people online over three or four nights. During this time, the researchers measured the quality of their sleep — how long they slept, how many times they woke up — and then assessed their desire to help others, such as holding an elevator door open for someone else, volunteering or helping an injured stranger on the street.

“Here, we found that a decrease in the quality of someone’s sleep from one night to the next predicted a significant decrease in the desire to help other people from one subsequent day to the next,” Ben Simon said. “Those with poor sleep the night prior were the ones that reported being less willing and keen to help others the following day.”

The third part of the study involved mining a database of 3 million charitable donations in the United States between 2001 and 2016. Did the number of donations change after the transition to Daylight Saving Time and the potential loss of an hour of sleep? They found a 10% drop in donations. This same dent in compassionate gift-giving was not seen in regions of the country that did not change their clocks.

“Even a very modest ‘dose’ of sleep deprivation — here, just the loss of one single hour of sleep opportunity linked to daylight saving time — has a very measurable and very real impact on people’s generosity and, therefore, how we function as a connected society,” Walker said. “When people lose one hour of sleep, there's a clear hit on our innate human kindness and our motivation to help other people in need.”

An earlier study by Walker and Ben Simon showed that sleep deprivation forced people to socially withdraw and become more socially isolated. A lack of sleep also increased their feelings of loneliness. Worse still, when those sleep-deprived individuals interacted with other people, they spread their loneliness to those other individuals, almost like a virus, Walker said.

“Looking at the big picture, we're starting to see that a lack of sleep results in a quite asocial and, from a helping perspective, anti-social individual, which has manifold consequences to how we live together as a social species,” he said. “A lack of sleep makes people less empathetic, less generous, more socially withdrawn, and it's infectious — there is contagion of loneliness.”

“The realization that the quantity and quality of sleep affects an entire society, caused by an impairment in prosocial behavior, may provide insights into our societal state of affairs in the present day,” Walker added.

This finding also offers a novel approach to improving these specific aspects of our society.

”Promoting sleep, rather than shaming people for sleeping enough, could very palpably help shape the social bonds we all experience every day,” Ben Simon said.

“Sleep, it turns out, is an incredible lubricant to prosocial, connected, empathic, kind and generous human behavior. In these divisive times, if there was ever a need for a strong, prosocial lubricant to enable the very best version of ourselves within society, now seems to be it,” said Walker, author of the international bestseller, Why We Sleep. “Sleep may be a wonderful ingredient that enables the alacrity of helping between human beings.”

“Sleep is essential for all aspects of our physical, mental and emotional lives,” Ben Simon said. “When sleep is undervalued in society, not only do we get sleep-deprived doctors, nurses and students, but we also suffer from unkind and less empathic interactions on a daily basis.”

In developed countries, more than half of all people report getting insufficient sleep during the work week.

“It is time as a society to abandon the idea that sleep is unnecessary or a waste and, without feeling embarrassed, start getting the sleep that we need,” she added. “It is the best form of kindness we can offer ourselves, as well as the people around us.”

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JOURNAL

PLoS Biology

DOI

10.1371/journal.pbio.3001733 

Non-nutritive sweeteners affect human microbiomes and can alter glycemic responses

Since the late 1800s non-nutritive sweeteners have promised to deliver all the sweetness of sugar with none of the calories. They have long been believed to have no effect on the human body, but researchers publishing in the journal Cell on August 19 challenge this notion by finding that these sugar substitutes are not inert, and, in fact, some can alter human consumers’ microbiomes in a way that can change their blood sugar levels.

In 2014, senior author Eran Elinav (@EranElinav) an immunologist and microbiome researcher at  the Weizmann Institute of Science and the German National Cancer Center (DKFZ) and his team found that non-nutritive sweeteners affected the microbiomes of mice in ways that could impact their glycemic responses. The team was interested in whether these results would also be found in humans.

To address this important question, the research team carefully screened over 1300 individuals for those who strictly avoid non-nutritive sweeteners in their day-to-day lives, and identified a cohort of 120 individuals. These participants were broken into six groups: two controls and four who ingested well below the FDA daily allowances of either aspartame, saccharin, stevia, or sucralose.

“In subjects consuming the non-nutritive sweeteners, we could identify very distinct changes in the composition and function of gut microbes, and the molecules they secret into peripheral blood. This seemed to suggest that gut microbes in the human body are rather responsive to each of these sweeteners,” says Elinav. “When we looked at consumers of non-nutritive sweeteners as groups, we found that two of the non-nutritive sweeteners, saccharin and sucralose, significantly impacted glucose tolerance in healthy adults. Interestingly, changes in the microbes were highly correlated with the alterations noted in people’s glycemic responses.”

To establish causation, the researchers transferred microbial samples from the study subjects to germ-free mice—mice that have been raised in completely sterile conditions and have no microbiome of their own.

“The results were quite striking,” says Elinav. “In all of the non-nutritive sweetener groups, but in none of the controls, when we transferred into these sterile mice the microbiome of the top responder individuals collected at a time point in which they were consuming the respective non-nutritive sweeteners, the recipient mice developed glycemic alterations that very significantly mirrored those of the donor individuals. In contrast, the bottom responders’ microbiomes were mostly unable to elicit such glycemic responses,” he adds. “These results suggest that the microbiome changes in response to human consumption of non-nutritive sweetener may, at times, induce glycemic changes in consumers in a highly personalized manner.”

Elinav says that he expects the effects of the sweeteners will vary person to person because of the incredibly unique composition of our microbiome. “We need to raise awareness of the fact that non-nutritive sweeteners are not inert to the human body as we originally believed. With that said, the clinical health implications of the changes they may elicit in humans remain unknown and merit future long-term studies.”

“In the meantime, we need to continue searching for solutions to our sweet tooth craving, while avoiding sugar, which is clearly most harmful to our metabolic health,” says Elinav. “In my personal view, drinking only water seems to be the best solution.”

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Cell, Suez et al. “Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance” https://www.cell.com/cell/fulltext/S0092-8674(22)00919-9

GlyNAC supplementation reverses mitochondrial dysfunction, oxidative stress and aging hallmarks to boost strength and promote health in aging humans

 

A randomized, double blind human clinical trial conducted by researchers at Baylor College of Medicine reveals that supplementation with GlyNAC – a combination of glycine and N-acetylcysteine – improves many age-associated defects in older humans and powerfully promotes healthy aging. This is relevant because until now, there have been no solutions toward improving many of these age-related declines in people.
 
Published in the Journal of Gerontology: Medical Sciences, the study shows that older humans taking GlyNAC for 16-weeks improved many characteristic defects of aging. This includes oxidative stress, glutathione deficiency and multiple aging hallmarks affecting mitochondrial dysfunction, mitophagy, inflammation, insulin resistance, endothelial dysfunction, genomic damage, stem cell fatigue and cellular senescence. These were associated with improvements in muscle strength, gait speed, exercise capacity, waist circumference and blood pressure.

“This is the first randomized clinical trial of GlyNAC supplementation in older humans, and it found that a wide variety of age-associated abnormalities improved in older adults supplemented with GlyNAC, while no improvements were seen in those receiving placebo,” said corresponding author Dr. Rajagopal Sekhar, professor of medicine - endocrinology, diabetes and metabolism at Baylor.

The improvements in oxidative stress, glutathione levels and mitochondrial function in the muscle tissue of older humans taking GlyNAC were similar to the improvements in organs such as the heart, liver and kidneys of aged mice supplemented with GlyNAC as reported in the researchers’ recent publication. Taken together, the results of these studies show that GlyNAC supplementation can improve these defects in many different organs of the body. “GlyNAC supplementation in aging mice increased their length of life mice by 24%,” said Sekhar. “Gait speed is reported to be associated with survival in older humans. Our randomized clinical trial found a significant improvement in gait speed in older humans supplemented with GlyNAC. This raises the interesting question of whether GlyNAC supplementation could have implications for survival in people”.
 
For the last 20 years, Sekhar has been studying natural aging in humans and animal models to understand why age-related declines occur and how to correct them. His work brings mitochondria, known as the batteries of the cell, as well as free radicals and glutathione to discussions about how they are connected. Sekhar’s work and discoveries could also help explain why we age and how to improve health while aging.

Mitochondria dysfunction, oxidative stress and aging

Mitochondria generate energy needed for supporting cellular functions. Therefore, normal mitochondrial function is critically important for a healthy life. Sekhar believes that improving the health of malfunctioning mitochondria in aging is the key to healthy aging. “Energy supports life and mitochondria provide energy. I believe that mitochondrial health is vitally important to our well-being, and maintaining mitochondrial health as we age should be a high priority in our efforts to improve overall health,” said Sekhar.

However, the ability of mitochondria to work well declines as we age. How to improve the ability of these failing mitochondria to work is not well understood, and therefore no solutions have been available. Sekhar’s group discovered earlier that supplementing GlyNAC in aged mice corrected malfunctioning mitochondria. However, to definitively determine whether GlyNAC supplementation benefited people, a placebo-controlled randomized clinical trial was required.

Sekhar and his team conducted and completed such a randomized clinical trial which found that older people have widespread mitochondrial damage and other age-associated defects compared to young people. After 16-weeks of GlyNAC supplementation, mitochondrial function of older people improve toward levels found in young people. This was accompanied by improvements in multiple additional outcomes as reported in the publication. Analysis of the molecular data from the trial suggests that the GlyNAC supplementation is able to fill cells with younger and more efficient mitochondria. “Collectively these exciting new discoveries hold great promise for improving our mitochondrial and general health as we age,” Sekhar said.

A second vital benefit offered by supplementing GlyNAC is that it also helps protect the body from an important problem called oxidative stress. Oxidative stress is caused by high levels of toxic waste products known as reactive oxygen species or free-radicals. Oxidative stress can damage our cells, membranes, lipids, proteins and DNA, and is very common in aging. Glutathione is a natural antioxidant. Glutathione is made every day inside our cells and it works by protecting cells from harmful oxidative stress. However, in older people, glutathione levels are very low and the harmful oxidative stress is very high. GlyNAC supplementation corrects glutathione deficiency and lowers oxidative stress in older humans back to youthful levels, thereby solving both problems.

Sekhar believes that the restoration of mitochondrial health and correction of oxidative stress with GlyNAC supplementation are two powerful reasons which help explain why so many other age-related defects improve. It also accounts for the wide spectrum of health benefits.

Taking GlyNAC is not the same as taking glutathione: Introducing the ‘Power of 3’

“It is really important to understand that this trial supplemented GlyNAC, and did not supplement glutathione,” says Sekhar. “This is because our body does not get its glutathione from food, but the body has to make its own glutathione every day. All our organs maintain different levels of glutathione in a delicate balance that favors health. Too little glutathione cannot fight the harmful oxidative stress, and too much glutathione could lead to harmful reductive stress,” said Sekhar. “This is why GlyNAC is a natural solution for correcting glutathione deficiency, because it provides the raw materials to help cells to make their own glutathione in just the right amount. We have seen that this repeatedly in all our prior studies supplementing GlyNAC, including this trial.”

“One of the intriguing questions from this trial is why so many improvements occur toward promoting health. We believe that this is due to the combined effort of three separate components – glycine, cysteine (from NAC) and glutathione, and not just due to glutathione itself. Glycine and cysteine are both very important for cellular health on their own, and GlyNAC provides both. Glycine and cysteine are building blocks to form glutathione, which also has health benefits. We believe that the improvements in this trial and in our previous studies are the result of the combined effects of glycine and NAC and glutathione, and we refer to this combination as the ‘Power of 3,” said Sekhar.

GlyNAC improves several aging hallmarks in aging
The population of older adults is expected to exceed 2.1 billion by 2050, according to the World Health Organization. This predicted increase in the older human population will result in a rise of the need for healthcare and will intensify the stress on healthcare systems around the world. To understand what causes unhealthy aging, scientific research has identified nine aging hallmarks that represent specific defects that are believed to contribute to health decline while aging.

“It is believed that correcting aging hallmarks could help people age in a healthier way,” Sekhar said. “However, we do not fully understand why these aging hallmarks occur in the first place, and therefore there have been no proven solutions via human randomized clinical trials to improve or correct aging hallmarks in aging humans.”

The aging hallmarks that improved are mitochondrial dysfunction, altered intercellular communication, nutrient sensing, loss of proteostasis, genomic instability, cellular senescence and stem cell fatigue. The study participants were instructed not to change their usual diet or physical activity; therefore, nothing changed except for the GlyNAC supplementation. “This tells us that benefits were due to GlyNAC supplementation. But we were really surprised to see so many aging hallmarks improve. This level of improvement offers clues as to how and why these aging hallmarks may be connected to one another,” says Sekhar.

GlyNAC improves muscle strength in aging

GlyNAC supplementation improved muscle strength in the upper and lower extremity and a trend toward increased exercise capacity. “These findings could have additional implications for improving the health of older humans, especially in terms of being able to be more physically active,” said Sekhar.  

“This study was effort intensive and took many years to complete. I take this opportunity to thank all my co-investigators, nursing staff, and everyone who helped with this trial. I especially thank all the trial participants who volunteered to participate in this research,” Sekhar said.

Sekhar led the study team consisting of Premranjan Kumar, Chun Liu, James Suliburk, Jean W. Hsu, Raja Muthupillai, Farook Jahoor, Charles G. Minard and George E. Taffet, all at Baylor College of Medicine. For this trial, Sekhar received funding support from the National Institutes of Health/National Institute of Aging, and philanthropic support from the McNair Medical Institute at the Robert and Janice McNair Foundation in Houston, TX.

Baylor College of Medicine holds a patent on GlyNAC, which has been licensed to Nestlé Health Science. GlyNAC is marketed in the United States by Nestlé Health Science under the name CelltrientTM Cellular Protect. Nestlé Health Science did not provide financial or material support for this research work.

As he moves forward, Sekhar plans to expand on his work to understand more about the health benefits of GlyNAC supplementation on cells, tissues and organs of the body. He plans on seeking funding to conduct larger clinical trials in more typical older humans to increase our understanding of how GlyNAC could improve health in aging. Additionally, as reported in their previously published exploratory study, Sekhar’s group found that GlyNAC supplementation in older humans could improve memory and cognition. He has studied this further in aged mice and found that GlyNAC supplementation appears to correct multiple age-related declines directly in the brain, and was associated with improvements in memory and brain health – a report on these emerging new and exciting findings is in development.

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JOURNAL

The Journals of Gerontology Series A

DOI

10.1093/gerona/glac135

Recreational runners benefit from adjusting their training based on recovery status

 

A study at the University of Jyväskylä, Finland, compared a traditional endurance training program with a program that was individually adjusted based on recovery status. Both groups improved their endurance performance after 12 weeks of training, but the individualized group improved their 10 km running time more. There were also fewer individuals within the individualized group who showed no significant change in endurance performance.

In endurance training, it is essential to find the right balance between the training load and the subsequent recovery. It is already known from previous studies that scheduling high-intensity interval sessions individually based on resting heart rate variability can be an effective method to improve endurance performance. However, there has been relatively little research on training programs that would adapt based on recovery status, and so far programs have not taken a more holistic view, looking beyond traditional heart rate measures to consider factors such as perceived recovery state.

In a recent study, a 12-week training period was conducted during which subjects trained either according to a program based on previous studies or according to a program that was individually adjusted based on recovery status. The training period was divided into two parts, the first focusing on low-intensity endurance training and the second on interval training. In the predefined group, the training and recovery weeks were all timed in the same way.

In the individualized group, each subject’s recovery status was assessed twice a week, after which the training load was decreased, maintained or increased from the preceding level. Changes in training were made based on whether the perceived recovery state, the nocturnal heart rate variability and the ratio between heart rate and running speed during the previous training sessions were within the desired limits. Changes in performance were monitored by an incremental treadmill test and a 10 km road running test.

Both groups improved their treadmill test performance and their 10 km running time over the 12-week training period. The most significant difference between the groups was observed in the 10 km running test, where the individualized group improved their time twice as much as the predefined group.

“The individualized group improved their time by about three minutes and the predefined group by about one and a half minutes,” says Olli-Pekka Nuuttila, doctoral researcher at the Faculty of Sport and Health Sciences. “In addition, individualized training appeared to reduce the risk of low training response. Training interventions often find some individuals whose performance does not improve as expected or even deteriorates from the baseline. In this study, for example, in the treadmill test, each subject in the individualized group improved their performance from baseline.”

The average training volume or training intensity distribution did not differ between groups. At the individual level, however, some of the individualized group programs were more demanding and some were less so than the predefined program.

“The results suggest that taking recovery state into account when designing training plans would seem to benefit recreational runners,” says Nuuttila. “In practice, this could mean, for example, training programs via a phone app or smartwatch that adapt to the individual’s own recovery state according to a model similar to this study or further evolved models.”

The study involved a total of 30 men and women aged 20 to 45 with a background in endurance training (16 in the individualized group and 14 in the predefined training group). The study was funded by the Foundation of Sports Institute and Polar Electro, whose heart rate monitors were used in the study.

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JOURNAL

Medicine & Science in Sports & Exercise

DOI

10.1249/MSS.0000000000002968