Exercise & the heart

Heart Rate Variability: Application in the Endurance Sports

June 30, 2017 By Larry Creswell, MD Leave a Comment

This past week, an excellent article by Charles Wallace, entitled “What’s Your Heart-Rate Variability? It May Be Time to Find Out,” was published in the Wall Street Journal. My good friend, exercise physiologist and coach, Alan Couzens, contributed on the practical aspects of using heart rate variability (HRV) in the training of endurance athletes generally, and his coached athlete, Inaki de la Parra, specifically.

Since then, several readers inquired about previous columns I’d written for Endurance Corner on the topic of heart rate variability, noting that links at my blog to those columns were no longer working. My apologies! I’d need my own IT person to keep track of the many old links.

Here’s part 2 of the original Endurance Corner columns….

Part 2: Application in the Endurance Sports

In previous columns I wrote about resting heart rate and heart rate recovery and more recently about the basics of heart rate variability (HRV), where we developed some basic definitions and terminology. Today’s column looks specifically at the use of HRV in endurance training. We’ll talk about how and when to measure HRV; how HRV might be used to help guide your training; and about some of the hardware and software tools that are available to help you make use of HRV.

Measuring HRV

HRV can be measured at any time of day, over any length of time, and with any desired relationship to exercise. For endurance athletes, we might consider measurements of 3 sorts: “resting,” “during exercise,” or “post exercise.” And keep in mind that we’re measuring HRV as our window into the body’s autonomic nervous system, with its parasympathetic and sympathetic components, hoping this can somehow be related to training.

One important consideration is the circadian pattern of HRV. HF and rMSSD are highest in the early morning, decrease throughout the daytime, to an afternoon low, then increase until the following morning. In contrast, LF/HF follows the opposite pattern, peaking in the afternoon. This circadian pattern has implications with regard to how and when HRV should be measured. In order to eliminate the influence of this circadian effect—and to focus more solely on the influence of the autonomic nervous system—daily (or weekly, etc.) measurements ought to be made at the same time of day.

The most commonly used—and best understood—measurement is the resting HRV. The ideal time for measurement is just after waking, while still supine. A recording of the EKG to gather R-R interval measurements is made for just a few minutes. The resting HRV can also be measured in the sitting or standing positions, but there is more variability, or noise, in these measurements. Whichever choice is made for body position should probably be used for all subsequent measurements.

The use of exercise HRV is limited because the instantaneous HRV is very much related to the intensity of exercise during the measurement. The use of post-exercise HRV is limited because these measurements tend to be influenced greatly by post-exercise blood pressure regulation that, again, is dependent upon the intensity of exercise preceding the measurement. It appears that exercise and post-exercise HRV indices might well be correlated to fitness level, but difficulties with establishing constant conditions during their measurement will limit their utility for most athletes and coaches.

Another important consideration is variability from measurement to measurement. The day-to-day variation in the time domain indices (eg, rMSSD) is much less than for the frequency domain indices (eg, LF/HF). As an example, the coefficient of variation for rMSSD may be as high about 10-12%. As a result, some authorities advocate using a rolling several-day average for rMSSD, rather than simply a single-day measurement.

Finally, it is important from a statistical standpoint, to have some idea about the smallest meaningful change for any of the indices. Again as just one example, the smallest meaningful change for rMSSD may be around 3%.

HRV and the Training Cycle

In the endurance sports, the use of HRV has been studied in 2 general settings—the short term and the longer term.

In the short term. On any given training day, intense exercise will lead to a decrease in HRV and this effect can persist for 24-48 hours or so. Based on this observation, some have suggested that intense training only take place again once the HRV has returned to its baseline. Indeed, there is some evidence that training guided by this strategy might result in better performance gains over some period of time. When using this strategy, though, it’s important to remember that factors other than the ANS (eg, sleep, hydration, environmental conditions) also play a role in the HRV and these factors should be kept in mind when interpreting the results. Some of the commercially available HRV devices are designed specifically for this application.

In the longer term. For many endurance athletes, training comes in cycles. There are block periods of trainings followed by some sort of rest. At the end of some blocks might come tapering before an event. The use of HRV to help guide training in these various phases of training is not yet particularly well understood. I can share some generalities, though.

Thinking about a cycle of training for moderately trained, recreational endurance athletes, moderate intensity training leads to increases in aerobic fitness and a corresponding increase in HRV. Over that cycle, we would also expect a gain in fitness or performance, a decrease in the resting heart rate, and an increase in the rate of heart rate recovery after exercise. For that same group of athletes, a taper, or reduction in training load might ordinarily lead to a subsequent increase in HRV.

There is particular interest in the possibility of using HRV as a tool for identifying negative adaptation to training—to avoid the problems of overreaching or overtraining. Unfortunately, the results of studies that were designed to produce training scenarios of overtraining have produced conflicting results; some have resulted in markedly decreased HRV and others have resulted in markedly increased HRV. As a generalization, though, we might expect that accumulated fatigue would be indicated by an increase in resting heart rate together with a variable effect on HRV and that overtraining might be indicated by decreases in both resting heart rate and HRV. In general, an otherwise unexplained reduction in HRV may be an indication of fatigue. Quantities such as the natural log of the rMSSD (Ln rMSSD) have been proposed as an index of fatigue, or a marker of “readiness to perform.”

Here’s the rub, though. In elite athletes and recreational athletes with long training histories, these typical changes have been less consistent. It turns out that HRV responses to training are not only specific to an individual but also to both the recent and remote training history. The most important observation is that the relationship between HRV and fitness is simply different in well-trained athletes: there can be increases in HRV with no corresponding increase in fitness over a training cycle and there can also be decreases in HRV despite increases in fitness.

Hardware and Software

A variety of hardware and software tools are available for athletes and coaches who are interested in using HRV to help guide their training plans.

Omegawave. In triathlon circles, Omegawave is probably the most familiar name in HRV technology. Their system for individual athletes includes a heart rate monitor/chest strap that communicates by Bluetooth with a subscription-based mobile software app. The device is used to make a 2-minute recording of the resting HRV. Then, using proprietary algorithms (invisible to the user), the software calculates an index of Cardiac Readiness along with Cardiac Readiness Elements that include “stress,” “recovery pattern,” and “adaptation reserves.” The software also generates a table of appropriate training zones based on heart rate and an index of aerobic readiness. Omegawave touts the utility of their system in helping athletes determine their “readiness to train.” I’ve used the Omegawave system and found it very easy to use. The down side, of course, is that it’s a bit of a black box. Athletes just don’t know exactly what’s being measured or reported.

BioForce HRV. Like the Omegawave system, the BioForce system includes a mobile app together with web-based software that are designed to work with a hear rate monitor (eg, Polar). An index of HRV, again not explicitly defined, can be measured during a 3-minute rest period and stored for comparison with succeeding days. Included with the system is a book, “The Ultimate Guide to HRV Training,” where training recommendations are based primarily on the day-to-day changes in HRV. Like the Omegawave system, the user is blinded to what exactly is being calculated or derived for the HRV index.

Ithlete. Another similar product is the ithlete HRV system which uses a proprietary heart rate monitor or finger probe, together with a mobile app, to calculate an index of HRV. ithlete offers the advice that a large drop in HRV from one day to the next should prompt the athlete to back off from training. Like the Omegawave and BioForce systems, the user is blinded to what exactly is being calculated.

Heart Rate Monitors. Some heart rate monitors (eg, Polar, Suunto) include a feature that allows for data collection and reporting on R-R intervals that serve as the basis for any HRV calculations.

Kubios HRV software. Made available for free download by the Biosignal Analysis and Medical Imaging Group at the University of Finland, and intended originally for use by scientific investigators, Kubios HRV software allows for calculation of the most common time and frequency domain measures of HRV. Inputs can come from an ASCII file of R-R interval data or from some standard heart rate monitor data files (eg, Polar, Suunto). This software is probably the best (and cheapest) tool for athletes who might want to derive particular measures of HRV and relate them to their training. The Kubios user’s guide includes not only instruction on the software but also general information about the underpinnings of the various HRV indices.

Physionet software. Another option for free, open-source software comes in the form of a HRV Toolkit from the Division of Interdisciplinary Medicine and Biotechnology at Beth Israel Hospital/Harvard Medical School. These tools do not have a graphical user interface like Kubios, but do allow for calculation of many of the relevant HRV indices and graphical representation of the results.

Some Thoughts and Recommendations

HRV technology might well be most useful for dedicated amateur and elite endurance athletes who are looking for additional ways to monitor their training, make day-to-day adjustments to their training patterns, and avoid the negative adaptations of overreaching or overtraining. But from what we know from the rather limited studies of elite endurance athletes, HRV may not have the same, predictable relationships to a training cycle that have been observed in less-trained recreational athletes and non-athletes.

In thinking about the hardware and software tools that are currently available, the Omegawave, Bioforce, and ithlete systems might be best suited for athletes who want to use HRV monitoring for the “short term” application I described above. A Kubios-based approach might be more suitable for athletes who want to use HRV monitoring during and through various training blocks. There seems to be a real opportunity for the heart rate manufacturers and the training data analysis/repository vendors (eg, TrainingPeaks) to offer some easy-to-use, mathematically transparent tools for everyday athletes.

Realize that none of this is particularly simple, at least not yet. The serious endurance athlete who wants to make use of HRV monitoring might do well to use a Kubios-based approach to track some indices for a season and to simply gain familiarity with the process. In so doing, you’d become aware of how various HRV indices related specifically to each phase of your training. You’d become aware of both positive and negative trends in that regard. You’d then be in a position to see how best to make use of HRV in conjunction with other markers like fatigue, performance, resting heart rate, exercise heart rate, and heart rate recovery.

There’s no doubt in my mind that the use of HRV technology will become more widespread in the endurance sports, particularly as we learn more about the real-world experiences of well-trained recreational athletes. Stay tuned.

Heart Rate Variability: The Basics

Heart Rate Variability: The Basics

June 30, 2017 By Larry Creswell, MD 1 Comment

I’ll reprint the Endurance Corner columns here, in 2 parts….

Part 1: The Basics

In a previous column, I wrote about the resting heart rate and heart rate recovery and how they can be used as indicators for monitoring athletes’ training status. At least 2 other heart rate-related indicators are also used for that purpose. I’ll leave the discussion about exercise heart rate to Alan Couzens, our resident Endurance Corner physiologist, but I wanted today to introduce the concept of heart rate variability (HRV).

In sports science circles, there has been a surge in interest recently in the use of HRV as a tool for monitoring athletes’ responses to training. The basic concepts have been around for decades, but technology—both software and hardware—is now becoming reasonably priced for individual athletes. The driving motivation has been a quest to identify physiologic markers that might help to optimize training and avoid overreaching or overtraining.

In today’s column, Part 1 of a 2-part series, I thought I’d offer a primer on heart rate variability for those of you who might be interested in this emerging technology. In Part 2, I’ll cover HRV applications in the endurance sports and describe some of the software and hardware tools that are now available.

Definitions and Terminology

First, we’ll need some definitions and terminology. Our starting point is the surface electrogram, or EKG, that reflects the electrical activity of the heart. The electrical activity for a couple heartbeats might look something like:

Entire textbooks are written about the EKG, but let’s simplify things here. By convention, with each heart beat there is a p-wave that corresponds to the electrical activation of the upper chambers of the heart, the atria. Next, there is a Q-R-S complex that corresponds to the electrical activation of the pumping chambers of the heart, the ventricles. The cycle is then completed with a T wave that corresponds to electrical repolarization of the ventricles before the next heartbeat. This cycle repeats over and over again.

The time between successive activations of the ventricles is reflected by the R-R interval, the time between successive R-waves of the EKG, and is usually expressed in msec. This is the quantity that most heart rate monitors measure to calculate the heart rate (in beats per minute) by:

Heart rate (beats per minute) = 60 / [R-R interval (in msec)/1000 ].

What’s interesting and relevant to our discussion here is that the R-R interval is not exactly constant. It varies from beat to beat, by a small amount. Said differently, the heart rate actually changes from beat to beat—thus the term heart rate variability.

Some Derived Quantities

We can record the EKG and measure each of the R-R intervals over any time period. A plot of these R-R intervals during the recording period is called a tachogram:

For purposes of athletes, we might do this for a few minutes, like shown in the example….or even for a whole day. Regardless, over a period of time the series of R-R intervals varies about a mean. In the example, the R-R interval varies about a mean of ~1000 msec, or a heart rate of 60 beats per minute. To better illustrate the distribution of the measured R-R intervals, we can generate a histogram of the R-R intervals:

In the so-called time domain, quantities such as the mean heart rate and standard deviation (SD), pRR50 (the percentage of R-R intervals that are >50 msec different from the previous beat), or rMSSD (the root mean square of differences between successive R-R intervals—the average absolute value change in R-R interval between beats—can each be determined. We say generically that HRV is increased when pRR50 or rMSSD are increased.

The time series of R-R interval measurements can be considered another way, though, in the so-called frequency domain. Using Fast Fourier Transformation (FFT), the original time series of R-R interval measurements (the tachogram) can be broken down into its time-dependent sinusoidal components:

The area beneath the curve is referred to as the power spectral density, expressed in msec². By convention, in humans there are ranges termed low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) for which power spectral density can be determined separately (again, the area beneath the corresponding portion of the curve). These values are called simply LF and HF. The ratio of LF to HF, or LF/HF is also a relevant derived quantity, as we’ll see below.

Why is HRV Physiologically Relevant?

The beat-to-beat variability of the human heart rate is governed, at least in part, by the autonomic, or involuntary nervous system, which has 2 components. The sympathetic nervous system acts on the heart to increase the heart rate and the parasympathetic nervous system acts on the heart to decrease the heart rate. In terms of HRV, HF is a reflection of the parasympathetic activity and LF is a reflection of the sympathetic activity. By extension, the LF/HF ratio is generally reflective of the balance between the parasympathetic and sympathetic activity.

Despite the importance of the autonomic nervous system in clinical medicine, the use of HRV has found very few applications in the clinical setting. While HRV has been proposed for such purposes as early identification of infection, prediction of risk for developing arrhythmias, prediction of risk of death after heart attack, and risk stratification in patients with diabetes, among others, none has become a part of modern clinical practice because of practical difficulties with HRV measurements and poor correlations with important outcome measures.

In Part 2, we’ll talk about applications of HRV to endurance athletes’ training specifically and I’ll share some information about the software and hardware tools that are available today.

Book Review: Haywire Heart

April 5, 2017 By Larry Creswell, MD Leave a Comment

Check out the recently published “The Haywire Heart” by Chris Case, John Mandrola, MD, and Lennard Zinn. The book is available at Amazon and other outlets.

You may recall that Case, Mandrola, and Zinn authored an article in VeloNews, entitled “Cycling to Extremes: Are endurance athletes hurting their hearts by repeatedly pushing beyond what is normal?” This was a terrific read. I wrote a previous blog post sharing my thoughts about the article and about the issue of arrhythmias and endurance sport, more generally. Their article generated much discussion in the cycling and broader endurance sports communities and the interest of readers served as the motivation for their new book.

This is a book about electrical problems in the heart–the various arrhythmias. Case, Mandrola, and Zinn are in a unique position to bring this topic to life because each has dealt personally with some form of arrhythmia. And as long time cyclists (and perhaps with some triathlon experience as well), they’re able fashion the discussion to the avid endurance athlete. From the medical perspective, the field of arrhythmias is rather complicated, both in terms of the underlying mechanisms of disease and the evaluation and treatment of affected patients, but here the authors have found a writing style that is captivating and accessible to the non-medical reader, while retaining much medical detail that will be of interest. I give them credit because this is hard to do!

I love the title. With an arrhythmia, the heart is truly “haywire.” Ignore the line on the cover, though, about “How too much exercise can kill you.” That’s unlikely to happen and there’s little in the book about that particular issue. Instead, focus on “what you can do to protect your heart.” That’s where the value lies here.

The book is organized into 9 chapters. In Chapters 1-3, the authors describe in detail how the normal heart works, outline how the heart adapts over time to endurance exercise, and introduce the medical aspects of heart attack and arrhythmias, especially for the endurance athlete. These sections are well-illustrated and are a great primer for any athlete interested in learning more about the heart.

Chapters 4-6 focus on the evidence of a link between long-time endurance exercise and arrhythmias, what to look for in yourself, and what it’s like to receive the diagnosis of an arrhythmia. Here, the authors speak from personal experience and their observations and advice are valuable.

Chapter 7 deals with the issue of exercise addiction. We know that exercise is generally healthy, but most of the benefits of exercise accrue with the first few hours per week. Why, then, do athletes exercise more? When does one become addicted? What are the implications? This is an interesting and pertinent discussion and might provoke some warranted introspection.

Chapter 8 covers the various treatment options for athletes with various arrhythmia problems. For athletes who don’t have trouble with arrhythmias, the discussion is educational in a broad sense. For those who do have arrhthymias, though, there is ample detail here to become educated and be better engaged with your doctor(s) as you sort out the best treatment for you.

Finally, in Chapter 9, the authors wrap up with their “takeaway” on how we might prevent arrhythmia problems.

One of my favorite aspects of the book is the inclusion of Case Studies sprinkled throughout the text, where the authors illustrate their points in a side bar with the personal account of an athlete. These stories bring us the human side of arrhythmias and show how difficult these problems can sometimes be.

This book is for….

the athlete with an arrhythmia problem. There’s a lot of familiar territory here as well as the opportunity to learn more. An educated patient is the ideal patient.
the athlete with simply an interest in the heart. I can’t think of a better resource to become educated about the workings of the heart, particularly as they relate to the endurance athlete.
the athlete (or the athlete’s spouse or parent) who’s afraid of causing harm to the heart through exercise. Be forewarned and be vigilant.

Related Posts:

Heart to Start, by James Beckerman, MD
The Exercise Cure, by Jordan Metzl, MD
Cardiac Athletes, by Lars Andrews

Returning to Exercise (and Training) After Heart Surgery

May 1, 2016 By Larry Creswell, MD 32 Comments

I’ve had a bunch of requests for a blog post on getting back to exercise or training after heart surgery. These requests usually come from: 1) athletes who are contemplating an upcoming operation and are already worried about if/when/whether they’ll be able to get back to exercise afterwards or 2) athletes who’ve recently had successful operations and are looking to become active once again, but are looking for reassurance that it’s safe to do so. I marvel every time I see an athlete patient get back to exercise after heart surgery, so I’m always encouraged by these inquiries.

For today’s discussion, let’s confine ourselves to what I call “conventional” heart surgery—the whole collection of heart operations that use a chest incision, with splitting of the breast bone (sternum), and make use of the heart-lung machine for cardiopulmonary bypass during the procedure. We’ll save for another day those procedures that are “less invasive” in some way, use some other incision or approach, and those that don’t make use of the heart-lung machine. As examples, I’m talking about common operations like coronary artery bypass grafting (CABG) or heart valve repair or replacement.

At the outset, we need to have a big disclaimer. Athlete patients are all different. Their operations are different, too—even when we’re talking about just the commonly performed operations. And because athletes and operations are all different, I can only generalize here.

If you’re an athlete patient, please use this post to become educated about some of the issues and help gather your thoughts for conversations with your own doctor(s). This is the only way to settle on plans that are right for you.

Athletes in this situation should remember that there are very real issues with the safety of exercise. My best advice is to take things slowly and consult with your doctor(s) frequently.

Athletes and Operations are Unique

Athletes who need heart operations can be different in many ways. Some need operation for congenital, or inherited, conditions they’ve had since birth (eg, atrial septal defect [ASD]). Others need operation for acquired conditions that take many years to develop (eg, coronary artery disease, aortic aneurysm). In still others, an emergency operation may be needed for some sort of acute problem (eg, aortic dissection).

In many cases, athletes will have conditions where the heart function is preserved, but some will have conditions where the heart has suffered some sort of damage, and become weakened, over time. Some athletes will be healthy except for their heart condition and others will have other medical conditions that affect not only the operation, but also the recovery.

Finally, athletes will come with all sorts of sports backgrounds and all sorts of future goals. Some will be young and others will be old. Some will be recreational athletes, some will be exercisers, and some will be competitive athletes. Some will have had high fitness levels before operation, and others will not. The demands of the various sports are different, too. Some have highly “dynamic” nature (eg, running). Others have a high “static” nature (eg, weightlifting).

Heart operations are different, too. In some cases, operations can be curative. In others, the operation might better be thought of as “mending a broken heart.” Moreover, in some cases the underlying heart condition can take a long time to improve, even if operation is successful.

For all of these reasons, there can be no “one-size-fits-all” prescription for return to activity, exercise, and training. Instead, the prescription must be individualized.

Healing Up

Things need to get healed up after operation. This should be obvious.

The surgical wounds need to heal after surgery. The skin incision ordinarily heals very quickly. With either skin staples or absorbable sutures beneath the skin, the surgical wound usually seals in the first few days. It’s worth paying attention to instructions for showering, bathing, and swimming. Any infection of the surgical wound can be a major setback to healing. Pay attention to instructions to watch for swelling, redness, or drainage that might be signs of infection.

Deeper, the breast bone (sternum) is like any other broken bone. We wire the sternum back together and in most cases, the bone knits back together just like any other broken bone. This is a process that takes many weeks, but we often say that the bone regains about 75% of its strength in the first month, so long as healing proceeds correctly. During the first month, we generally restrict activities that place stress on the sternum as it heals. We ask patients to avoid pushing, pulling, reaching, or even just carrying heavy objects (more than 10 pounds). Many surgeons also restrict driving for the first month. All of these activity restrictions are important because exercise early after operation must usually involve the lower body, rather than the upper body.

Deeper still, the heart itself must heal up. Regardless of the exact operation, the handiwork here usually involves needle and thread. The tissues are sewn together or new materials (eg, heart valves) are sewn into the heart. Although the tissues or devices are fixed securely in place, it takes many weeks or even months for the affected tissues to heal completely. Your surgeon will be in the best position to comment on the expected period of time that will be needed for healing and to offer advice about any longer term risks to the affected tissues, devices, or prosthetics used that might come with various forms of exercise.

One final point is that healing may be impaired in some patients. Conditions such as diabetes, a suppressed immune system (eg, from illness or medications such as steroids), or even just poor nutrition before operation can delay healing substantially.

Is the heart mended? Or good as new? Does the disease continue even after the operation?

Thinking ahead to physical activity after operation, one very important consideration is: how healthy is the heart now? Have we cured the problem? Or have we mended the problem? Or, perhaps, have we introduced some new problem?

The important question to consider is: Does my current heart situation place me at increased risk for a future problem? And, if so, how big is that risk?

As one example, sometimes an athlete will need operation to correct an atrial septal defect (ASD), an inherited condition. If this condition is found before any damage has occurred to the heart or lungs, operation is curative and athletes can generally return to any form of sports activities after they’ve healed up.

As another example, sometimes an athlete will need coronary artery bypass surgery after a heart attack, or acute myocardial infarction (MI), in medical terms. The “plumbing” can be fixed with operation so that blood flow is restored past all (or most) of the blockages in the coronary arteries. It turns out, though, that it can take up to 2 years for the ruptured plaque that caused the MI to become stabilized. During that time, the best advice might be to limit strenuous exercise because of the increased risk of repeat MI.

In yet another example, sometimes an athlete will need operation for repair of an aortic aneurysm. Most often, a portion of the enlarged aorta is “repaired” by replacing the blood vessel with a synthetic, fabric substitute. After successful operation, though, there may still be mild enlargement of the remaining aorta that deserves surveillance over time for possible enlargement. Sports activities with a high “static” component (eg, weightlifting), where there can be large increases in the blood pressure, may not be advisable, for fear of accelerating aortic enlargement over time.

These are just 3 examples. The scenarios are virtually endless.

New Medications

For some athletes, things can be so “normal” after heart surgery that no new medications are needed. Sometimes, medications that were required before the operation are no longer needed. These athletes are fortunate.

For other athletes, though, new medications can be needed either because of the underlying heart condition or because of new hardware that’s been added. As an example, aspirin, beta blockers, and statins are often recommended for athletes who’ve had operation for coronary artery disease. Each of these medications will have implications for the athlete. As another example, blood thinners like warfarin (Coumadin) might be prescribed for an athlete with a mechanical heart valve. The anticoagulants also bring a potential risk of unwanted, serious bleeding in the event of bodily injury. This is a factor which must be weighed when settling on what types of physical activity are safe.

Cardiac Rehabilitation

Cardiac rehabilitation, or “rehab” for short, is a supervised program that includes medical evaluation, development of a physical activity program specific for the patient, educational services, and individual and group exercise where the vital signs and EKG can be monitored. The structure of these programs may vary by location, but will usually involve both an inpatient phase and an outpatient phase.

At many heart surgery programs, the inpatient phase of cardiac rehab begins within the first couple days after operation, with both educational and exercise components. There are usually educational offerings about nutrition, medications, lifestyle modifications, and community resources. There is also an exercise component that is tailored to the patient, usually involving walking at first, where there is close monitoring of the vital signs, the heart rhythm, and the oxygen level in the blood stream. It’s important early after operation, together with the patient and family, to establish expectations and goals about physical activity.

Cardiac rehab continues with an outpatient phase, where patients can enroll in a monitored exercise program, often in a group setting, with several sessions per week. Athletes may sometimes fail to see the value in such a program, but these programs can actually provide some much needed structure to the early return to exercise. Most importantly, these programs can provide confidence for the athlete that once they leave a structured setting, things will still be okay with their heart and safety during exercise. I’d recommend a full cardiac rehab program for all athletes who are looking to return to exercise after operation.

For most patients, walking is the most appropriate exercise early after operation, with an emphasis on moderate exertion and increasing duration.

Support

Having a good support system is important for any patient after heart surgery. It’s particularly true for the athlete who is returning to a formal exercise or training program after heart surgery. You can envision this support system as having a set of layers.

Closest to home, athletes will benefit from a family that helps to encourage a return to physical activity and works to make this possible. Family is usually the best support for ensuring continued good nutrition, ensuring restful sleep (including naps), and seeing to other various needs after the patient returns home from the hospital.

When it comes to returning to structured, independent exercise, I believe that a group setting is often best. We all know that it’s more motivating when we have friends to meet for the morning run or ride. In the case of athletes with recent heart surgery, it’s also reassuring for the athlete to know that company is nearby if some sort of medical problem crops up during an exercise session. Even if this possibility is unlikely, a group of fellow exercisers can provide some needed confidence.

Being able to share experiences with other athletes who’ve had similar surgery can often be helpful, even if those athletes aren’t close to home. There are a variety of support groups with an online presence, but two of my favorites are the Ironheart Foundation and Cardiac Athletes. Both offer an opportunity to network with similar athletes, learn from their experiences, and also have a forum to “give back.” You’re not alone. Many other athlete patients are dealing with the same or very similar situations.

Lastly, for athletes who are looking for some good reading material, one good resource is a book entitled “Heart to Start,” by cardiologist James Beckerman, MD. I’ve written a review about this book previously here at the blog. The book describes a gradual, structured path to resuming aerobic exercise and conditioning once cardiac rehab is completed.

Follow-up

It’s wise for athlete patients to put together a robust framework of medical support as they return to physical activity after heart surgery. Your “team” should include at least your heart surgeon, your cardiologist, and your primary care provider. At the beginning, there might also be a nutritionist, your cardiac rehab specialist, or physical therapist, as well. Perhaps you can think of other important team members as well.

Continuous dialog with your team is essential. Only you will be able to describe your goals and ambitions and ask for feedback about the advisability and safety issues. Don’t assume that your doctor(s) will understand what it means to train for the masters national swimming championship or a marathon or a 70.3 triathlon. If you envision several hours of aerobic exercise as well as strength training each weak, be prepared to describe this in detail, with expected exertion levels or heart rates, so that your doctor(s) can know exactly what you have in mind. Don’t hold back.

Athletes should arrange for periodic visits with their doctor(s) so that they can discuss their plans for physical activity, share their experiences, both good and bad, develop plans, agree on any restrictions, and monitor progress. This is good advice for any athlete, but particularly good advice for athletes who have had heart surgery.

In thinking about what sorts of exercise or training is safe for their athlete patients, doctors don’t always have a bunch of accumulated scientific evidence to rely upon. I’ve written previously here at the blog about consensus recommendations about the safety of sports for young, competitive athletes with various cardiac conditions. These recommendations weren’t developed specifically for adult, recreational athletes after heart surgery, but they may provide a starting point for discussion. Often, though, doctors must rely upon judgment and personal experience with similar patients.

Warning signs of a problem

I’ve talked previously about 5 important warning signs of potential heart problems: chest pain/discomfort, unusual shortness of breath, palpitations, blacking out (or nearly so), and unusual fatigue. Athletes should be vigilant about these general warning signs and report them to their doctor(s).

There may also be additional warning signs to watch for, that are very specific to the type of surgery an athlete has had. Some examples would include:

For those with a mechanical heart valve, stroke symptoms (temporary or permanent loss of sensation or muscle weakness) would be important
For those with coronary artery disease, return of angina symptoms (chest pain/discomfort) would be important
For those with aortic aneurysms, return of chest, back, or abdominal pain would be important
For those with arrhythmias, return of an irregular heartbeat or palpitations would be important.

Sometime in the first few weeks after operation, you should have a discussion with your doctor(s) about any specific warning signs that are most important for you. And then you should be vigilant.

Summary

Let me summarize the important points:

Each athlete’s situation will be different
Whatever the approach to returning to activity, pay attention to getting healed up, as a first priority
Participate in a cardiac rehab program
Consider your “new,” current heart situation as you make plans about the safety of exercise
Rely on your support network as you return to physical activity
Assemble a medical “team” to help as you return to physical activity
Make a list and be vigilant about warning signs that are specific to your circumstance

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In the Medical News: Does Heart Function Suffer in Long-term Endurance Athletes?

April 17, 2016 By Larry Creswell, MD 19 Comments

Background

Moderate amounts of exercise produce a multitude of health benefits. Both the American Heart Association (AHA) and World Health Association (WHO) now recommend 150 min per week of moderate intensity exercise for adults.

Some recent observations, though, have raised the question: when it comes to exercise, can there be too much of a good thing? And, more specifically, can too much exercise somehow be harmful to the heart. With the increased popularity of adult recreational and competitive sports–particularly in cycling, running, and triathlon–there is a growing number of adults who are pursuing exercise far in excess of the AHA and WHO recommendations. The questions surrounding the issue of “too much exercise” are very pertinent.

A few recent articles in the popular press summarize some of the findings and frame the debate:

Can Too Much Extreme Exercise Damage Your Heart?–at Cleveland Clinic online
Can Too Much Exercise Harm the Heart?–by Gretchen Reynolds at NY Times Well Blog
Is Too Much Exercise BAD for the Heart?–by Anna Hodgekiss at The Daily Mail
Extreme Exercise and the Heart–by Lisa Rosenbaum at The New Yorker

The worrisome observations have generally been made in small numbers of symptomatic athletes, in groups of athletes whose athletic history–or “dose” of exercise is poorly characterized, or in studies that were designed for some purpose other than determining the effects of “too much exercise” on the heart.

I’ve said previously that these observations deserve our attention, but that we really need more targeted investigation into this issue. In a study just released online (ahead of print) in the medical journal, Circulation, Philipp Bohm and colleagues from the Institute of Sports and Preventive Medicine at Saarland University in Germany bring us an important new look at “extreme” exercisers.

The Study

This new study focuses on a group of 33 healthy, male, Caucasian competitive elite master endurance athletes. This group of athletes was selected so that it included only athletes with a 10+ year continuous training history of 10+ hours per week; the average training was 16.7 hours per week and the average training history was 29 +/- 8 years. These athletes had an average age of 47 years (range, 30-60 years). This group of athletes included:

Sixteen were former elite professional athletes
One Ironman world champion and several 2nd and 3rd place finishers
The world record holder at the long distance triathlon
A 2nd ranked cyclist of the Vuelta a Espana (Tour of Spain)
Six Olympic athletes in the sports of triathlon and rowing
A former winner of the Munich Marathon.

A control group consisted of 33 healthy Caucasian men who were pair-matched for age, height, and weight. This control group was selected to include only individuals who exercised <3 hours per week.

All of the subjects underwent a comprehensive evaluation that included:

History and physical examination (to exclude any athlete with a history of overt heart disease, high blood pressure, smoking history, or other risk factor for heart disease)
Resting EKG
Cardiopulmonary exercise testing
Echocardiography, including tissue-Doppler imaging and speckle tracking
Contrast-enhanced cardiovascular magnetic resonance imaging (CMR).

Interestingly, none of the athletes presented with, or reported a history of, atrial fibrillation.

There were several unsurprising, and expected differences between the athletes and the controls. First, the resting heart rate (HR) for the athletes (48 +/- 7 beats per minute) was slower than for the controls (65 +/- 11 beats per minute). Second, the size of the athletes’ hearts was significantly greater. The left ventricular (LV) mass for the athletes’ hearts (188 +/- 26 g) was significantly greater than the controls (124 +/- 23 g). Similarly, the right ventricular (RV) mass for the athletes’ hearts (70 +/- 13 g) was significantly greater than the controls (49 +/- 11 g). Among the 33 athletes, 22 met a traditional definition of “athlete’s heart,” with a heart volume of 13+ mL/kg of body weight. As expected, the VO2 max of the athletes (60 +/-5 ml/kg/min) was significantly greater than controls (37 +/- 6 ml/kg/min).

The important results of the study were those that showed no difference between the athletes and the controls. With echocardiography, there was no difference between athletes and controls in LV longitudinal strain or RV longitudinal strain–measures of the strength of contraction. Using CMR, there was no difference between athletes and controls in LV ejection fraction (EF) or RV EF–again, measures of the strength of contraction. One athlete (3%) had a LV EF slightly less than normal, at 45%. No athletes or control subjects had abnormalities of the RV that could be suggestive of the potentially life-threatening problem of arrhythmogenic right ventricular cardiomyopathy (ARVC). One athlete (3%) had late gadolinium enhancement (LGE) on CMR that suggested previous, asymptomatic inflammation of the pericardium, the sac in which the heart sits. LGE analysis showed no evidence of unusual fibrosis or scarring in either athletes or controls.

My Thoughts

Kudos to the investigators here. The study is apparently self-funded. It’s expensive to perform this kind of testing; in the United States, the costs of this study would easily run into the many hundreds of thousands of dollars. Kudos, too, to the editors at Circulation. There is a tremendous bias against publishing so-called “negative” studies, where no important differences are found between study and control groups. Many “negative” studies are left on the editing room floor–and we never hear about them.

This is an important study because it is the first to gather and study a group of long-term endurance athletes with a substantial, and defined, training load over an extended period of time. The results deserve our attention. At nearly 17 hours per week of exercise or training, these athletes obviously far exceeded the contemporary recommendations for 150 minutes of moderate exercise per week. Just doing some quick math, the average cumulative exercise “dose” is more than 25,000 hours. As I’ve said many times before, it’s worth asking the question if such an exercise pattern can be harmful to the heart over the long term. This is a terrific group of athletes to study in order to help answer that question.

We must keep in mind that, with just 33 athletes, this is a small study. With only 33 athletes, it’s obviously possible to miss something that would be found in the 34th athlete. We must also keep in mind that the study only involves male athletes. Female athletes are not immune from heart problems and deserve study, too.

It is a striking finding that no athlete was found to have atrial fibrillation–either now, or in the past. Moreover, no athletes experienced arrhythmias during the cardiopulmonary exercise test. A number of previous studies have reported a 2- to 5-fold increase in atrial arrhythmias among long-term endurance athletes. Like the current study, all of those previous studies have involved small number of athletes. None, though, have focused on athletes like these, with such extensive exercise and training histories. In my opinion, endurance athletes broadly can take some comfort from the findings of this new study with regard to the potential risk of atrial arrhythmias.

It’s noteworthy that the LV and RV function of the athletes was no different than the controls. One athlete had mildly depressed LV function, for reasons that are not clear. In short, though, the study found no evidence of cardiac damage–at least, in terms of the pumping function–that accrued over the long term. We know that there is some depression of LV and RV function immediately after an intense bout of exercise (eg, marathon, long-distance triathlon, long-distance cycling event), but we also know that these changes resolve within days to weeks afterward. The current study argues against the hypothesis that repeated episodes of intense exercise (ie, many marathons or triathlons over a lifetime) might result in a decrease in LV or RV function. Again, this is encouraging news for endurance athletes.

Finally, the CMR and LGE results are important. Aside from the 1 athlete with possible previous pericarditis, there were no worrisome findings of fibrosis or scarring that might be attributable to injury from repeated episodes of intense, strenuous exercise. These LGE findings are at odds with some observations of unexplained fibrosis in other cohorts of long-time runners, even if the consequences of such findings remain uncertain. This area of investigation deserves further attention. For now, I’d say that long-time participation in endurance sports does not necessarily result in unexplained fibrosis in the heart.

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