In our search to find well-being (the balance of compassion and thought) we discovered the magic of meditation, the wonderful benefits of prayer, and the healthy infusion of mind, body, and spirit through the consumption of tea. Throughout these discoveries, we have come across various writings, videos, and artistic presentations which further this pursuit. To be of further service to you, we have compiled an assortment of these works which you may find beneficial. Please enjoy as we have.
What Is Heart Rate Variability (HRV) & Why Does It Matter?
Heart rate variability (HRV) seems to be on everyone’s lips these days, at least those who are interested in monitoring their own or their clients’ sleep, recovery, performance or overall health. The phenomenon itself is not new, but its use in everyday language and in widely available devices is a fairly new development. Many professional and consumer wearables list HRV as one of the markers that they measure, and sports, wellness and performance coaches and professionals should understand the basics of this fascinating phenomenon. Without diving too deep into the science of HRV, this blog will discuss HRV from a practical perspective: what it is, what it can tell you about your body’s physiology, and what you should be aware of when interpreting it. Future blogs in this series will broaden the topic to practical applications and the somewhat complex relationship of HRV to things like stress and recovery.
Heart rate variability or HRV is the physiological phenomenon of the variation in the time interval between consecutive heartbeats in milliseconds. A normal, healthy heart does not tick evenly like a metronome, but instead, when looking at the milliseconds between heartbeats, there is constant variation. In general, we are not acutely aware of this variation; it’s not the same as the heart rate (beats per minute) increasing and decreasing as we go about our daily business. You can get a sense of your HRV if you feel your pulse on your wrist while taking a few deep breaths in and out: the interval between beats gets longer (heart rate slows down) when you exhale and shorter (heart rate increases) when you inhale, a phenomenon called respiratory sinus arrhythmia. In addition to respiration, HRV is influenced acutely for example by exercise, hormonal reactions, metabolic processes, cognitive processes, stress and recovery.
How to Measure HRV?
Reliable HRV analysis requires accurate measurement of each heartbeat and the time between beats. There are different technologies for calculating HRV, but it’s beyond this blog to discuss them comprehensively. If you want to dig deeper into the principles of measuring HRV and different HRV variables, I recommend for example the Task Force article on heart rate variability. In short, ECG-based methods detect the R wave in the QRS complex and calculate the time between R waves (R-R interval; Fig. 1). This is what, for example, the Firstbeat Bodyguard does: it can detect the heartbeat at 1 ms accuracy (1000HZ) for very accurate HRV analysis in most people of different body types and age groups. Most of the widely available wearable devices use PPG or photoplethysmography to detect the heartbeat optically by measuring the wave of blood flow, for example from the wrist or ear, and then calculate the inter-beat interval or IBI. Comparison between different methods is always challenging, and this is certainly true with HRV – and beyond the scope of this blog. However, different methods and devices, if used correctly and systematically, can produce interesting and useful information for the user.
Heart Rate Variability and the Autonomic Nervous System
HRV is regulated by the autonomic nervous system (ANS), and its sympathetic and parasympathetic branches, and it is commonly accepted as a non-invasive marker of autonomic nervous system activity. The sympathetic branch of the ANS is the stress or fight or flight system, getting us ready to act, react, and perform – to meet the different demands that life throws at us. The parasympathetic side is characterized as the rest and digest system that allows the body to power down and recover “once the fight is over”. The sympathetic branch activates stress hormone production and increases the heart’s contraction rate and force (cardiac output) and decreases HRV, which is needed during exercise and mentally or physically stressful situations. Conversely, the parasympathetic branch slows the heart rate and increases HRV to restore homeostasis after the stress passes. This natural interplay between the two systems allows the heart to quickly respond to different situations and needs.
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Why Does Heart Rate Variability Matter?
In a normal, healthy situation, HRV should increase during relaxing activities, for example meditation or sleep, when the parasympathetic nervous system should dominate (see Fig 2 for an example). On the other hand, HRV naturally decreases during stress, when elevated sympathetic activity helps the body keep up with the demand. Thus, HRV is typically higher when the heart is beating slowly, and lower when the heart starts to beat faster, for example during stress or exercise. The HRV level changes naturally from day to day, based on the level of activity and amount of, for example, work-related stress, but if a person is chronically stressed or overloaded – physically or mentally – the natural interplay between the two systems can be disrupted, and the body can get stuck in a sympathetically dominant fight state, with low HRV and high stress hormone levels, even when the person is resting. This is very consuming on the body and can result in various mental and physical health problems.
Genetic factors explain about 30% of the overall HRV level, but a person can improve their individual HRV by improving their health, fitness, stress management and recovery skills. High HRV is generally considered an indicator of a healthy heart, and higher HRV has been found in many studies to be associated with reduced morbidity and mortality and improved psychological well-being and quality of life. We must live with what the genetic lottery has given to us, and even if some general reference values are available, comparison to other people’s HRV values is not meaningful. The good news is that lifestyle has a powerful effect on HRV. We can take active steps to improve our lifestyle, be physically active and strive for a better balance in our lives, and in the process, will likely see improvements in our HRV as well.
Practical Applications for Utilizing HRV?
Firstbeat has developed ways of utilizing HRV in real-life conditions. The HRV data is turned into valuable and understandable feedback that helps to perform better, make correct training and coaching decisions, and improve wellbeing and health. Firstbeat Lifestyle Assessment is a professional-grade stress and recovery monitoring tool for wellness coaching. Firstbeat Sports is a complete solution to optimize training load and recovery for sports teams. Firstbeat is also trusted by top brands in wearable markets to help you make the best possible health, fitness and performance decisions. You can find Firstbeat features in over a hundred products.
Take Time for Tea: For Health and Well-being (FN1328, Revised Sept. 2015)
Taking time to strengthen relationships over a cup of tea can be good for emotional and physical health. The tea warms your body and adds health-promoting substances to the diet. The time spent in conversation with a friend or family member can strengthen those important social bonds that enhance health and well-being.
A warm-weather evergreen, Camellia sinensis is the source of tea leaves for all varieties of regular tea. The degree of processing or oxidation of fresh tea leaves determines the type of tea produced.
Green tea has minimal processing. The leaves are steamed, rolled and quickly dried prior to packaging. Thus, green tea is not oxidized and is characterized by its delicate taste and light green color. Widely enjoyed by people in the Orient, it is becoming more popular worldwide.
Black tea is produced by allowing the tea leaves to be fully oxidized or fermented (about 60 to 90 minutes). Black tea is characterized by its hearty flavor and deep amber color. Popular black teas are Earl Grey, English Breakfast, Darjeeling and Orange Pekoe.
Oolong (red) tea is produced by allowing a shorter time for the processing or oxidation to occur (about 30 minutes), compared with black tea. Thus, the color and taste of oolong tea can be considered midway between green and black tea. Oolong (red) tea is popular in the Orient.
White tea is produced in China and utilizes young tea leaves and unopened buds. It produces a delicate brew with a soft, velvety flavor with little caffeine.
Herbal tea is produced from various native herbs or plants, utilizing the leaves, stems or roots, depending upon the intended use. Native cultures around the world have used herbal teas for medicinal purposes.
History and Cultural Practices
Tea is the primary beverage of many cultures. Tea appears to have originated in China, with exports for at least 1,000 years. Other Asian countries also have a long history related to tea production and use. The Japanese tea ceremony is a traditional ritual, influenced by Zen Buddhism, in which a highly trained tea practitioner serves green tea to a small group of guests.
English Tea Customs
In the 1600s, an English trade company was established and began to bring goods, including tea, from the Orient to England. England began to use tea, and soon it became the primary beverage. Afternoon or low tea was established as an elegant snack served in the late afternoon around 3 or 4 p.m., with small cakes, assorted sweets, small bread-and-butter sandwiches and tea. Initially, the upper classes primarily served low tea.
The English served high tea later in the afternoon or early evening. It was the main meal of the day for the middle and lower classes. In the early 1700s, tea became a staple of trade between the English colonies in America and England. Tea was among the goods and services England taxed to help pay for the French and Indian War. The tax on tea eventually led to the Boston Tea Party and opened the colonies’ armed rebellion against England.
Potential Health Benefits
Researchers have found an association between those who drink tea, especially green tea, and a reduced risk of certain chronic diseases, such as cancer, heart disease, stroke and diabetes. The substances in tea associated with these health benefits are called polyphenols, mainly flavonoids. Studies suggest catechins, a type of flavonoid, are the component primarily responsible for the health benefits of tea. All three types of tea (green, black, oolong) contain catechins, but green tea has about three times more catechins than black or oolong tea.
Heart and Blood Vessel Disease
Population studies indicate tea may help reduce the risk for heart and blood vessel disease. Tea’s potential role in reducing risk may include the following: (1) help improve blood vessel function, (2) help reduce blood clotting and/or (3) help reduce the level of oxidized cholesterol known to promote heart disease processes.
Studies of the role of tea in cancer prevention in human populations have not been conclusive. However, laboratory research suggests that tea may play a role in reducing cancer risk in various ways: (1) reducing the initial development of cancerous cells, (2) reducing the growth of cancerous cells and/or (3) promoting the early death of cancerous cells.
Researchers believe the caffeine in tea is the component that lowers the risk of Type 2 diabetes. Caffeine appears to enhance glucose metabolism and thus assist in control of blood sugar. Therefore, drinking suggested amounts of tea or coffee may help reduce the risk of Type 2 diabetes or help improve management.
Amounts of Tea
Health experts have suggested variable amounts of tea from 2 to 10 cups per day to promote health, but no definitive recommendation is available. However, even small amounts of tea contribute polyphenols (antioxidants), which have been found to enhance health.
Note: Those having iron-deficiency anemia may need to limit the amount of tea they drink because chemicals in tea are known to bind iron and decrease its absorption.
How to Brew the Best Cup of Tea
- Bring freshly drawn water (preferably not softened or hard) to a boil in a glass or enamel container (not aluminum), remove from the heat and cool for one to three minutes.
- In a teapot made of glass, china or porcelain, place about 1 teaspoon of tea leaves for every 6 ounces of water. Allow the tea leaves to move freely in the water (referred to as “blossom”) and then strain when poured. If using an infusion basket or tea ball, select one large enough to allow the leaves to move.
- The length of brewing time can affect flavor. Usually steep for three to five minutes. Experiment with the amount of brewing time to get the desired flavor, or follow the manufacturer’s directions.
- When time allows, warm the tea cup before serving the tea.
For recipes to accompany tea, such as quick breads, click on “Recipes.”
This publication was authored by Debra K. Lee, Extension agent, and Jane U. Edwards, former nutrition and health specialist, NDSU, 2007