“The subject of athletics has not been understood until recently; nor has the best method of training been investigated,” Dr. Sargent told a Harvard audience on March 6, 1896. Dr. Sargent seems to be suggesting that everything about athletic training was now settled. 121 years later, however, there is still so much to learn about our amazing bodies, and how to maximize what they can do.

One useful measure is resting heart rate (RHR). A low RHR (along with optimal SpO2) is the hallmark of cardio health. RHR is just what it sounds like, the measure of how many times your heart beats (per minute) when you are at rest. (as opposed to heart rate variability (HRV), which measures the variation between beats.)

You can measure it with wearable tech or kick it old school (2 fingers at the neck) Either way, knowing your baseline RHR will help you monitor progress, and identify problems, before other symptoms emerge.

A normal resting heart rate for adults ranges from 60 to 90. When it comes to RHR, it important to know how to lower resting heart rate. Elite athletes have RHR in the 50s, 40s, even 30s. High RHR is associated with an increase in risk of death. But can you change your RHR? If so, how? And by how much?

How Can You Change Your Resting Heart Rate?

The good news? Yes, you can lower your resting heart rate.

The 3 best ways to reduce your RHR?

(Need help remembering? Picture yourself riding a bike. (exercise) Your stress melts away. (relaxation) You’re so stress-free you fall into a deep slumber. (sleep.)

Exercise

“It is very possible and even common to lower your resting heart rate through exercise,” says Tyler Spraul, a Certified Strength and Conditioning Specialist and Head Trainer at <a href="http://Exercise.com" rel="nofollow">Exercise.com</a>. “The type of exercise is not important, as long as you are challenging your cardiovascular system with your workouts.”

The 4 most Important types of exercise for health include strengthening, stretching, balance, and aerobic exercises. And exercise doesn’t just lower your RHR. Harvard Medical School reminds us that exercise will also ward off depression, enhance your sex life, sharpen your wits, and improve your sleep.

“As you train your cardiovascular system,” Spraul explains, “you will increase its efficiency and capacity. What ends up happening is that your heart is able to do more work with less effort (pump more blood throughout your system while requiring less energy and exertion to do so), so your resting heart rate goes down.“

It’s important to find activities you like, and to mix it up, to avoid boredom and make sure you’re working all parts of your body. Interval training (alternating intensive workouts with periods of rest) is an especially effective way to lower your RHR.

Sleep

Sleep is emerging as a new frontier of health, with implications for cardio health, cognition, mood and even mortality. That’s right, a good night’s sleep over time can forestall death.

Disturbed sleep negatively impacts heart health and can increase RHR. Sleep has been shown to promote cardiac health and mood, which in turn has a protective function across all aspects of your health and performance. Sleep also protects against weight gain, which can increase your RHR.

Relax!

Whether we are resting, or stoked with adrenaline during a ‘fight or flight response’, our hearts are in play.

Reduce stress, and your RHR will naturally fall. Increase stress? And it will rise, regardless of sleep and exercise. Stress in teens (measured by parental corporal punishment) was found to increase adolescent resting heart rate variability, while positive parenting helped improve RHR and HRV.

Yet reducing stress is easier said than done.

Some stress is beyond our control. But that makes it even more important to control what we can, and incorporate stress reduction as a daily component of our healthy lifestyle.

These interventions are widely successful to reduce stress.

• Breathing exercises
• Exercise (there’s that word again)
• Higher physical fitness was found to have a protective effect against training distress in collegiate soccer players.
• Meditation
• Yoga.
• A recent study of yoga and children showed yoga practices of even short duration (3 months) can “reduce anxiety status and decreases resting heart rate” by affecting the autonomic nervous system.
• Nutrition (avoid sugar, caffeine and alcohol)
• Relaxation Apps

How Quickly and by How Much?

A recent poster on Researchgate asked, “Is it possible to decrease the heart rate by 20 bpm in 6 months” The consensus? Yes, through exercise, but you need to be healthy to start, and work super hard.

G. Filligoi of Sapienza University of Rome recommends the relaxation route: “You can decrease heart rate by respiration exercises, yoga, meditation. I would suggest some self-consciousness approach in order to reduce the anxiety, nervous stress, and similars.”

Not everyone agrees it’s possible. “In my opinion,” says Oscar Fabregat-Andrés of MED Hospitales, “it is not possible to modulate baseline heart rate in such magnitude, because although exercise is able to regulate autonomic system, "vagal tone" necessary to reach this rate is not performed in 6 months.”

Does Lowering your RHR Make you Healthy?

If a low RHR is a sign of health, does that mean lowering your RHR automatically makes you healthy? No, but it’s evidence you’re on the right track. Measuring RHR is a safe, non-intrusive way to track the success of your fitness regime, and spot trouble early.

“A low resting heart rate doesn't necessarily lead to better health in and of itself,” says Spraul, “but it can be used more as an indicator of the effectiveness of your training methods.”

This effectiveness can be positive, or not. “If you are doing workouts that challenge your cardiovascular system and your resting heart rate decreases over time,” he says, “that is a good sign that you are doing the right things.” But it’s important to measure it regularly, even, especially, if you are training hard. An unexpectedly elevated RHR can be a sign of overtraining. “Sometimes the resting heart rate can actually increase,” Spraul cautions, “which is a sign that you have over-stressed your body's systems and may need to focus on better recovery or

Back to the Basics

Back in 1896, Dr. Sargent wasn’t so far off the mark. “The modern idea of training,” he told his Harvard audience, “is to seek things “which will contribute to health and strength: diet, sleep, bathing, proper clothing and exercise.” “Exercise with energy,” he concluded, “to stimulate the heart and lungs and increase respiration and circulation.” Some things never change.

Exercise stimulates the heart, in a good way. And RHR is a key measure of how well it works.

Stem cells, famous for replenishing the body’s stockpile of other cell types throughout life, may have an additional, unforeseen ability to cache memories of past wounds and inflammation. New studies in the skin, gut and airways suggest that stem cells, often in partnership with the immune system, can use these memories to improve the responses of tissues to later injuries and pathogenic assaults.

“What we are starting to realize is that these cells aren’t just there to make tissue. They actually have other behavioral roles,” said Shruti Naik, an immunologist at New York University who has studied this memory effect in skin and other tissues. Stem cells, she said, “have an exquisite ability to sense their environment and respond.”

But when those responses go wrong, they may cause or contribute to a variety of enduring health problems involving chronic inflammation, such as severe allergies and autoinflammatory disorders.

Most tissues in the body contain small reservoirs of long-lived stem cells that can divide and specialize into myriad cell types as required. A stem cell in the skin, for example, can divide and give rise to lineages of cells that produce pigment or keratin, cells that form the sweat glands, or even the flexible barrier cells that allow the skin to stretch when the body moves. Serving as miniature factories for other cell types seemed to be stem cells’ primary function, and because they need to stay versatile, an underlying assumption has been that they have to be “blank slates,” unchanged by their histories. But now a new picture is starting to emerge.

In August, a Nature paper by Boston-area researchers offered fresh evidence for a kind of memory in stem cells, and some of the first for the phenomenon in humans. The team, led by the single-cell sequencing pioneer Alex Shalek and the immunologist José Ordovas-Montañes, both at the Massachusetts Institute of Technology, and the immunologist Nora Barrett at Brigham and Women’s Hospital, had set out to understand why some people suffer from debilitating chronic allergies to airborne dust, pollen and other substances. Most people experience at most a passing bout of coldlike symptoms from these irritants, but about 12 percent of the population has a severe reaction that persists all year and results in uncomfortable polyps or growths.

The work is the first step in the team’s larger quest to understand chronic inflammatory diseases, such as asthma and inflammatory bowel disease, in which the immune system continues to launch unnecessary attacks even after the initial challenge is over. These types of autoinflammatory disorders have long been blamed on the immune system, which is thought to overreact to a perceived threat. But the Boston team suspected there might be a cause in the tissue itself.

They began by taking cells from the inflamed nasal cavities of people with chronic sinusitis and comparing them to cells from healthy control subjects. After collecting about 60,000 cells from 20 different people, they sequenced RNA molecules taken from individual cells to determine which genes were active in them. In the stem cells from the sinusitis patients, they saw that many of the active genes were associated with allergic inflammation — in particular, the genes were targets of two immune mediators called interleukin 4 (IL-4) and interleukin 13 (IL-13). These are small molecules that immune cells like T and B lymphocytes typically use to communicate with one another.

The fact that the targeted genes were active in stem cells meant that the stem cells were apparently in direct communication with the immune system. A hunch that this communication might have an effect on the chronic nature of the disease led the researchers to a further set of experiments.

They removed cells from the airways of allergy patients, grew them in culture for about five weeks, and then profiled their gene activity. They found that the genes involved in allergic inflammation were still active, even though the allergic threat of dust and pollen was long gone. In addition, the researchers described many of the cells as “stuck” in a less-than-fully-mature state.

For Shalek, this result signals “that stem cells may transfer ‘memories’ to future generations of cells and this can cause near-permanent changes in the tissue they replenish.” This process invites comparisons to the immune system: B cells and T cells draw on their experiences with infections they have previously repelled to fight off new ones more effectively. Similarly, stem cells may retain a record of past assaults to sharpen their responses next time. But in the case of the allergy patients, that memory apparently becomes maladaptive. It may keep stem cells perpetually signaling to the immune system that an attacker is there, creating a feedback cycle that promotes inflammation and polyps.

According to Shalek, an understanding of which cells become “bad actors” and how their response propagates throughout a tissue should lead to more effective interventions. In fact, in their paper they were able to test the effects of an antibody that blocks IL-4 and IL-13 on the stem and secretory cells of an individual with nasal polyps. They noted a substantial restoration of gene expression associated with healthy tissue, a promising step toward the development of future therapies.

“This opens a new paradigm where we don’t only focus on the self-renewal potential of these cells but on their potential interaction with their surroundings,” said Semir Beyaz, an immunologist at Cold Spring Harbor Laboratory. Beyaz was not involved in the study by the Boston group but has made similar findings in the gut: In a paper published in Nature in 2016 he demonstrated that the intestines of mice on a high-fat diet produced a greater number of stemlike cells than did those of mice eating less fat. When dividing, the intestinal stem cells also seemed to add to their own numbers more frequently rather than producing more differentiated cells, a change that has been linked to diseases like cancer.

“Functionally, we are realizing that cells can be tuned,” Naik said. “Immunologists are starting to understand that immune reactions take place in tissues, and the way tissues respond to this is at the level of the stem cell.”

A few years ago, in collaboration with stem cell biologists, Naik looked at the effects of prior injury and inflammation on wound healing in mice, in the hope of understanding whether experience with inflammation affects stem cells. As described in their 2017 paper in Nature, she and her colleagues discovered that if patches of skin on mice were inflamed and allowed to heal, subsequent wounds to that same spot would heal 2.5 times as quickly, an effect that could last as long as six months.

In that experiment, Naik explained, the memory retained in the stem cells was beneficial because it was “tuning cells to be more powerful at healing wounds and regeneration.” But the flip side of this finding, as Shalek, Barrett and Ordovas-Montañes had observed, is that “if you teach [the cells] bad behaviors … they are going to remember those bad behaviors as well,” she said.

How the stem cells are storing these memories is unknown; in both the allergy and the wound healing studies, the mechanism appears to involve some modification of the DNA that makes certain genes more or less accessible to activation. Naik found that the DNA in the skin stem cells of the twice-wounded mice contained many regions that were less tightly packed, which usually indicates gene activity, and some of those open regions were retained long after the inflammation was over.

As Naik and her colleagues discussed recently in a review paper for Cell, stem cells in a wide range of tissues engage in a chemical “dialogue” with the immune system, with both sides — and potentially many other cell types — pooling their information to cope most effectively with changing conditions. Whatever the details of those conversations might be, all the evidence points to stem cells playing a central role in helping to make tissues more adaptable by preserving some record of their history.

“It makes more sense that a tissue would just learn from its experience,” Naik said. “That way it doesn’t have to reinvent the wheel every single time.”