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What are the Effects of Hydration on HRV, HRR, and RHR?

Hydration is everything, especially when it comes to protecting your heart’s health. If you want to reap the benefits of a healthy heart you will want to make sure your hydration levels are in an optimal range on a consistent basis.

What's the connection between hydration and the heart?

The heart circulates blood and transports nutrients throughout the body. While doing its work, it pumps about 2,000 gallons worth of blood every day. You may be wondering: what fuels this functioning? Don’t look too far; it’s water.

Water is a vital and highly underrated nutrient for healthy living that aids in transporting nutrients and other fluids all through the body. Abundant research also tells us that it lubricates and cushions the joints and internal organs, regulates body temperature, provides structure to cells and tissues, and promotes cardiovascular functioning.

When you’re not well-hydrated, your heart has to work twice as hard to pump blood through the blood vessels to the muscles. This strain on the heart causes your heart rate and blood pressure to rise. You may even experience heart palpitations, or irregular heartbeats, just because your heart is trying to work more efficiently.

A 2017 study examining the effect of water on cardiac workload and potential gender differences confirms that drinking water influences the heart’s functioning and reduces its workload in healthy adults. And this function cuts across all genders. Similarly, this study suggests that drinking water induces various heart-related responses, such as decreased heart rate and increased resistance and heart rate variability. Interestingly, another study also observes that hydration invokes cardiorespiratory behaviors in healthy subjects.

Hydration triggers positive heart-related outcomes, and you can observe this in a person’s heart rate recovery (HRR), heart rate variability (HRV), and resting heart rate (RHR). But what are these measures, and why are they essential parameters for checking the heart’s functioning in adults? Let's take a deeper look:

Heart Rate Variability (HRV)

Heart rate variability (HRV) is a simple and noninvasive measure of the time difference between each heartbeat calculated in milliseconds (ms). So if your heart beats 62 times in a minute, your HRV tells you the variation in time between each beat.

The autonomic nervous system (ANS)—consisting of the parasympathetic and sympathetic nervous systems, also known as the fight-or-flight and rest-and-digest mechanisms—controls this fluctuation in the length of each heartbeat interval. It’s no wonder considerable evidence shows that the HRV is a “reliable reflection of the physiological factors modulating the normal rhythm of the heart.”

A high HRV signals that your parasympathetic nervous system is in charge because your body is in a relaxed and good recovery state. As your heart slows down, the variation between each beat becomes higher. In contrast, a low HRV reflects the dominance of the sympathetic nervous system. It shows that your body is in a fight-or-flight mode, and that’s why there’s a smaller difference in time between each beat, as it’s working harder and faster.

It is an incredible tool for monitoring heart-brain interaction and autonomic health. According to a 2014 study, an optimal HRV mirrors cardiovascular fitness, resilience, healthy function, wellbeing, and adaptability in a person.

Heart Rate Recovery (HRR)

The Journal of the American Heart Association describes heart rate recovery (HRR) as “the rate at which heart rate decreases within the following minutes after the cessation of physical exercise, and reflects the dynamic balance and coordinated interplay between parasympathetic reactivation and sympathetic withdrawal.” It’s usually measured 1 minute or 2 minutes after physical activity. If your heart rate was at 130 per minute immediately after exercise and dropped to 95 beats per minute, your HRR is 35 beats in one minute.

The fitter you are, the more quickly your heart recovers from strenuous activity. An accelerated HRR signals that your autonomic nervous system is in excellent working condition because it shows that your sympathetic nervous system swiftly deactivates for your parasympathetic to take over to tell your body to relax and your heart to beat slower.

HRR is also a simple way to monitor physical fitness and cardiovascular strength. According to a 2016 study, the speed of HRR is an essential predictor of aging and mortality. It’s no surprise that another study concludes that HRR is greater in well-trained athletes but deficient in patients with chronic heart failure.

Resting Heart Rate (RHR)

Resting heart rate (RHR) is the number of times your heart beats in a minute when in a completely relaxed state. Age, environment, blood volume, heart condition, medication, fitness, and body position are all factors that affect RHR. But generally, the fitter you are, the lower your RHR.

Experts say that a normal RHR is approximately 60 to 80 beats per minute. If your RHR is higher than usual, it may be a sign that you’re ill, tired, stressed, or your immune system is weak. What’s more, considerable research highlights the predictive value of RHR and suggests that it can monitor autonomic activity.

How does drinking water affect your heart?

Drinking water produces various heart-related responses which, according to scientific reports, can be best explained by its impact on the autonomic nervous system.

These described changes can be observed in HRV, HRR, and RHR.

Here, we’ll run through studies that not only establish the connection between hydration and the heart but also explain how water intake affects HRV, HRR, and RHR.

Hydration works to boost HRV performance any time of the day, and numerous studies back this up.

A study investigating the influence of drinking water on post-exercise heart rate variability recovery observed that water intake as a post-exercise autonomic recovery measure promotes higher HRV scores throughout the recovery period. Explaining that the risk of severe cardiovascular events usually increases after physical exertion, mentions that water intake during or after exercise might be an effective intervention for protecting against post-exercise cardiovascular events.

What’s more, a study suggests that dehydration triggers the parasympathetic nervous system and reduces overall HRV. Similarly, another 2017 study on the influence of hydration on sleep, nocturnal heart rate variability, and cognition, suggests that not hydrating before bedtime reduces heart rate variability at night.

Finally, a 2015 study compared dehydration and rehydration after exercise on college athletes’ heart rate variability and metabolic rate. The college athletes were assigned to a dehydration group and a rehydration group. Those in the dehydration group were not given any water after exercise, but the rehydration group had enough water to compensate for lost fluid during exercise. Four hours later, the HRVs of both groups were assessed, and the result showed that only the dehydration groups had significantly lower HRV.

You guessed right—water intake accelerates HRR after strenuous activity, and numerous research comes to this conclusion.

A study looking at the cardiorespiratory effects of drinking water during and after exercise highlighted the importance of hydrating during and after exercise to reduce cardiac workload, increase HRR, and promote respiratory function. Likewise, another study suggests that hydrating after prolonged exercise is necessary for boosting recovery.

Drinking water helps the heart work more effectively to maintain blood flow throughout the body, and you can observe this in how optimum hydration reduces RHR over time.

A 2017 study suggests that drinking water decreases heart rate and systolic blood pressure, thus reducing cardiac workload. Similarly, the results of another study exploring the effects of drinking water on blood pressure, cardiovascular variables—HRV and RHR—and salivary immunoglobulin A in healthy adults showed that drinking water significantly reduces heart rate.

How much water do you need?

There’s no gold standard for how much water you should take to meet perfect hydration status. Your water needs depend on different factors, including your health status, body weight, the weather, your activity levels, your environment, pregnancy and breastfeeding status, and more. However, the Institute of Medicine (IOM) recommends the following guidelines:

  1. Men should take in a total of 3.30 liters of water.
  2. Women should take 2.30 liters of water.  
  3. Pregnant women should take an additional 0.30 liters of water.
  4. And breastfeeding women should take an additional 1.10 liters of water.

Water is one of the cheapest and easily accessible nutrients that optimizes daily functioning. By prioritizing your daily water intake, and maintaining proper hydration levels, you will promote healthy heart function, as well as, every other organ in your body will maintain healthy function.

Please utilize the infographic at right on your journey towards optimal hydration!

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