Athlete's Heart Blog

A Preseason Check-up (Specifically for Men)

February 5, 2018 By Larry Creswell, MD Leave a Comment

This is the time of year I get inquiries about pre-season medical check-up’s. I’ve written previously on this subject, including how to find a doctor in your area. I’m frequently asked, though, exactly what type of check-up is needed. Here’s my take.

Today, let me focus specifically on adult male recreational athletes. I’ll deal specifically with women in a follow-up post.

First, in terms of screening adult recreational athletes for sports-related heart risks, adult men are the group where we might expect to get the most “bang for our buck.” We know that men account for the vast majority of victims of sports-related sudden cardiac death, not only in large populations involving all types of sports, but also in very specific sports such as long-distance running and triathlon. There’s a very real reason to be looking for hidden heart disease in male athletes.

Second, in contrast to women, “healthy” men in their 20’s, 30’s, 40’s, and even 50’s are unlikely to make periodic visits to the doctor (except for injury) and very often do not have a current primary care provider (PCP). It may have been years—perhaps back to high school or college—that many men last had a complete physical exam in some context other than for a musculoskeletal injury, which typically requires a rather narrow focus. As a result, there’s often been little opportunity for discussion between adult male recreational athletes and a healthcare provider about any heart risks associated with sports participation.

Let me share how I would approach a pre-season check-up for an adult male recreational athlete who does not already have a PCP….

Although I’m a heart specialist, here I would need to put on my generalist hat to make the most of the encounter.

I would have 3 goals:

Identify any cardiovascular conditions that required further evaluation or treatment as well as any risk factors for future heart disease that could (and should) be modified;
Make an assessment of the patient’s cardiovascular risks of exercise in order to offer appropriate advice about safe forms of exercise; and
Identify any non-cardiovascular conditions that required follow-up with another doctor.

Before the Office Visit

One of the most important parts of a check-up is sharing what we call the “medical history,” an accounting of everything medically-related that’s already happened to a patient. This would include:

Past medical history (childhood illnesses, adult illnesses, surgical or other procedures)
Immunizations
Injuries
Medications and supplements
Allergies
Family history (illnesses that run in the family)
Personal and social history (smoking, drinking, sexual activity and habits, substance use/abuse, work history, travel history)
Review of symptoms (yes/no answers to a long list of questions about current symptoms).

In addition, I would also want to collect information about insurance coverage, the names and contact information for any other current and previous medical providers, and an outline of an athlete’s current exercise habits.

Depending upon the complexity of a patient’s situation, gathering all of this information could be rather time-consuming. So, in order to make the most of our available face-to-face time at the upcoming office visit, I find it helpful to collect as much of this information as possible well ahead of the office visit. I like to use 2 forms:

A general purpose medical history form such as the Health Care Consumer Questionnaire.
American Academy of Family Physicians Preparticipation Physical Evaluation forms. These forms are used ordinarily for secondary school-based screening programs, but I am fond of the first page of the History Form, which asks a series of questions (#5 through #16) related specifically to heart risk. I ask patients to complete items #1 through #51 on the first page and to discard the other pages.

When I’ve received these completed forms, I would review them and consider the possible need to gather additional information ahead of the office visit such as:

records from other physicians or hospitals
results from any heart-related diagnostic tests that may already have been completed (eg, ECG, chest x-ray, echocardiogram, Holter monitor, stress test, laboratory tests, pulmonary function tests, carotid Doppler studies, coronary calcium scoring CT scan).

Lastly, I would make a determination about any new diagnostic testing that may be helpful on the day of the office visit and schedule those tests, if any, for the morning of the office visit. If I think such testing will be helpful, I would have a telephone call with the patient ahead of the visit to explain the need for these tests.

At the Office Visit

I would plan for an office visit of approximately 45 to 60 minutes.

The first portion of the office visit is devoted to an interview. I generally spend half of the visit time on the interview. We often say that the medical history provides 80%+ of the clues to diagnosis.

First, I ask what motivated the patient for wanting the visit. There are many possible motivations. Next, we would have a chance to review the information that had already been provided about the patient’s medical history. I would take the time to clarify and better understand anything in the history that was specifically related to the heart. We would focus on those history items and on any symptoms related to exercise. I would finish by asking the patient if there were any additional, specific concerns that we should address at this visit.

The second portion of the office visit is devoted to a physical exam. Here, I would offer a complete, head-to-toe physical exam, but with special emphasis on the cardiovascular system. The exam would include:

Measurement of the height, weight, and vital signs (blood pressure, heart rate, respiratory rate, temperature)
Screening neurologic exam
Examination of the head, neck, ears, eyes, nose, and throat
Respiratory exam
Cardiovascular exam (heart, carotid arteries, abdominal aorta, arteries of the arms/legs)
Abdominal exam, including check for hernias
Genito-urinary exam
Rectal and prostate exam, in men older than 40 years
Examination of the skin

The third portion of the exam is devoted to a discussion, or wrap-up. Here, we would discuss my findings from the medical history and the physical exam and my assessment of the patient’s overall and heart health.

For the majority of patients–those who do not have any heart-related symptoms or any abnormal physical exam findings–we would spend some time discussing the utility of screening tests such as ECG, echocardiogram, laboratory testing (eg, fasting glucose, fasting serum lipid levels), or stress testing, along with the advantages, disadvantages, and potential costs. Together, we would decide if any of these tests would be helpful. There is a place for such screening tests, but only with thoughtful discussion first.

For other patients, we might identify some new heart-related condition–or at least the possibility of one. As examples, we might find that the blood pressure is elevated or note the presence of a heart murmur. In this situation, we would talk about what sort of diagnostic tests might be needed to further clarify a problem and perhaps what treatment(s) would be needed for any conditions we discovered. Needless to say, there are many potentially useful tests, depending upon the patient’s circumstances, so we won’t go into detail here. In the case of potential inherited disorders, we might need to consider evaluating other family members as well.

In either situation, if additional testing were needed we would make a plan for getting those tests completed. We would also plan for how I would share those results with the patient (eg, by telephone or during a follow-up visit). I would ordinarily make plans to visit with the patient again to discuss the results of any important testing and to resume with our wrap-up once all of the important information was at hand. If more specialized heart care were needed, I would discuss referral to the appropriate specialist (eg, general cardiologist, electrophysiologist, interventional cardiologist, specialist in congenital heart disease) and, in some cases, I would turn over the patient’s care to that specialist.

Next, we would discuss how the patient’s overall and heart health related to his/her plans for exercise and sports participation. Together, we would settle on a list of activities that would be “safe” and, likewise, settle on a list of any activities that should be avoided. We would talk about potential warning signs of heart troubles and how to be vigilant for these. If the patient required a “doctor’s letter” or some sort of pre-participation form to be completed, we would go over that form together and review its requirements. I often complete such letters or forms and return them to the patient by mail sometime after the visit.

We would then make an inventory of any other medical problems (that were not heart-related) that needed follow-up and work together to settle on an appropriate action plan. Examples of such medical problems could include: colon cancer screening in men older than 50 years, that would require a gastroenterologist visit; eyesight troubles that might best be evaluated by an ophthalmologist; periodic screening for sexually transmitted illnesses, which might best be accomplished by a primary care physician; dental care which would best be provided by a dentist; and depression, that might best be evaluated by a psychiatrist. The list of possibilities is virtually endless; this is why there can be tremendous value in having a PCP.

Before we finish the wrap-up, I would take time to have a discussion about any questions or concerns the patient brought. I usually suggest that patients bring a written set of questions that we can answer these one by one.

Finally, I would make a recommendation about when the patient should next be seen for another check-up. For “healthy” patients–those without chronic medical conditions that require monitoring–I generally suggest a check-up every 3 years for men <40 years old, every 2 years for those 40-50 years old, and every year thereafter.

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More on Triathlon Fatalities–A Scientific Report

September 18, 2017 By Larry Creswell, MD 4 Comments

Readers here at the blog will know that I’ve had a long-standing interest in triathlon fatalities. My interest was originally sparked by media reports and the paradox that seemingly healthy and fit triathletes might die on race day.

I was involved with an internal review of this problem at USA Triathlon (USAT), the governing body for the sport of triathlon in the United States. In 2011, that task force issued a formal report and set of recommendations for athletes, event organizers, and USAT itself. Those written recommendations are still valuable today as we work to reduce the number of triathlon race-related fatalities.

In this week’s edition of Annals of Internal Medicine, I joined with Drs. Kevin Harris and Barry Maron from the Minneapolis Heart Institute in reporting on “Death and Cardiac Arrest in U.S. Triathlon Participants, 1985-2016: A Case Series.” In this scientific report, we’ve gathered information about 122 athletes who died and another 13 athletes who suffered cardiac arrest but survived during triathlon races in the United States over the past 3 decades. This is, by far, the most comprehensive scientific report on this subject.

Special thanks go to the leadership at USAT which recognized the importance of this issue, has been proactive in working to reduce the number of race-related fatalities, and was extraordinarily helpful to our investigative team as we assembled the information for our new report.

The Important Observations

Victims were 47 +/- 12 years old
85% were men
Almost 40% were first-time triathlon participants
There were no elite or professional athletes among the victims
The overall rate for fatalities or cardiac arrest was 1.74 per 100,000 participants (2.40 for men, 0.79 for women). For comparison, the rates of cardiac arrest (including fatalities) are approximately 1.0 per 100,000 participants in marathons and 0.3 per 100,000 participants in half marathons.
The fatality risk in triathlon increases exponentially with age; the fatality rate was 18.6 per 100,000 participants among men 60+ years old
Fatality rates were similar for short, intermediate, and long-distance races
The majority of deaths (74%) occurred during the swim segment; smaller numbers of deaths occurred during the bike or run segments or after finishing the race
Among 22 fatalities occurring during the bike segment, 15 were due to traumatic injuries
At autopsy, clinically relevant (but presumably previously unrecognized) heart/vascular disease was found in many victims

A Recipe for Doing Better

We should focus on two strategies for reducing the number of fatalities: 1) we should work to prevent incidents of race-related cardiac arrest and 2) we should work to improve the survival rate for any such victims of cardiac arrest. Athletes, physicians, event organizers, safety personnel, and sport governing bodies can all play an important role.

Athletes should:

Make certain that their participation in a particular race is in keeping with their health, both chronic and acute, as well as their ability and preparation.
Consider their heart health before participating. This may be particularly true for first-time participants and for men who have reached middle age. For older men, testing for “hidden” coronary artery disease (CAD) or other forms of cardiovascular disease may be appropriate.
Assess their health on race day and consider not racing if they are “sick.” Symptoms, particularly systemic symptoms like fever, are related to DNF rates in other sports settings.
Be prepared for the rigors of a triathlon swim. It is important to be a capable swimmer and to have practiced open water swimming in advance of the race.
Think to STOP at the first sign of medical troubles (unexplained shortness of breath, chest pain/discomfort, or light-headedness), particularly during the swim segment.

Physicians should:

Be aware of the risks of participating in triathlon and be in a position to counsel their athlete patients about those risks in the context of the patient’s specific health situation.
Consider the potential value of cardiac screening, particularly for occult CAD in men who have reached middle age. Evidence-based screening protocols are not yet available, so an approach will need to be individualized. In most cases, an evaluation of the traditional risk factors for CAD would be appropriate and in some cases, additional testing such as calcium-scoring cardiac CT or stress testing may be appropriate. Athletes who are just beginning an exercise program should receive special attention in this regard.

Event organizers should:

Develop a robust safety plan, particularly for the swim segment, that enables prompt (near instantaneous) identification of a lifeless victim, and then rescue of that individual to a location where CPR, defibrillation, and advanced life support can be provided.
Have a communication system for all individuals involved in race-day safety.
Rehearse the safety response to a lifeless victim, especially for the swim segment.

Race-day safety officials should:

Be trained in CPR and use of the AED.
Be familiar, through rehearsal, with the communication and safety plans.

Sports governing bodies should:

Provide education for athletes, event organizers, medical directors, and volunteer safety officials about life-threatening race-day emergencies.
Develop rules and sanctioning requirements that promote athlete safety.

Reference:

Harris KM, Creswell LL, Haas TS, Thomas T, Tung M, Isaacson E, Garberich RF, Maron BJ. Death and cardiac arrest in U.S. triathlon participants. Annals of Internal Medicine 2017 (in press).

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Should You Race When You’re Sick?

July 23, 2017 By Larry Creswell, MD Leave a Comment

We’ve had a fair amount of discussion here at the blog about long-term health, chronic heart conditions, and how exercise may or not be safe. We haven’t talked much, though, about acute general medical conditions, such as simply being “sick.”

Should you race when you’re sick? And, if you do….what might the consequences be?

I had a recent conversation with Chad Asplund, MD, the medical director for one of the Ironman 70.3 races, and Jon Drezner, MD, team physician for the Seattle Seahawks and an editor for the British Journal of Sports Medicine. We were talking about making a list of the concrete steps that triathletes could take to avoid serious medical problems on race day. Dr. Drezner drew my attention to a scientific report from last year that addressed this issue in long-distance running.

Let’s take a look at the study.

The Study

The team of investigators, from Cape Town, South Africa, is involved in the race-related medical care for a collection of on- and off-road running events ranging from “fun runs” to the 56-km Two Oceans Marathon, involving more than 25,000 runners each year. Over the past several years, this group has focused on studying this athlete population with an eye toward identifying, introducing, and testing interventions that might decrease the risk of race-day medical complications in participating runners. Collectively, their work has become known as the SAFER (Strategies to reduce Adverse medical events for the ExerciseR) studies. I’ve previously written here at the blog about the SAFER I study that looked at the “medical toll” of running races.

In the SAFER IV study, the investigators studied the impact of pre-race acute medical illness and do not start (DNS) and do not finish (DNF) rates for runners who competed one year in the 10-km or 22-km trail runs or the 21.1-km or 56-km Two Oceans events (1).

In the 3-5 days before each race, participants were offered the opportunity to complete an online questionnaire about any acute medical symptoms or illnesses that were present pre-race. The questionnaire included both systemic symptoms (headache, general muscle pains, cough, general joint pains, fever) and non-systemic symptoms (sore throat, runny nose, general tiredness, blocked nose, diarrhea, sore ears, abdominal pain, nausea, wheezing, bladder infection, skin rash, vomiting).

Among the participants, 7,031 runners completed the questionnaire. Any runners who reported symptoms received by email some educational material that suggested they not return to running until all symptoms were gone and they felt well again.

The Findings

A total of 19% of respondents reported at least one symptom during the pre-race period; this included 7.5% who reported systemic symptoms. The remaining 81% reported no symptoms (the control group).

In the control group, the DNS rate was 6.6%. In the symptomatic group, the DNS rate was 11.0%. Interestingly, despite the availability of the educational information for the symptomatic group (that recommended not exercising until runners felt well), 89% of those athletes started the race. For those runners who reported any systemic symptoms, the DNS rate was 15.1%.

In the control group, the DNF rate was 1.3%. In the symptomatic group who started the race, the DNF rate was 2.1% (1.6 times greater than control). For those runners who reported any systemic symptoms and who started the race, the DNF rate was 2.4% (1.9 times greater than control).

The investigators concluded: 1) symptoms of acute illness were relatively common during the pre-race period; 2) despite such symptoms and despite educational materials that discouraged participation, most athletes chose to start the race; and 3) pre-race symptoms of acute illness significantly increased the chances for a DNF.

My Take on The Study

This study is intriguing because it is the only prospective study to address the impact of pre-race acute illness on race-related performance, in any sport. First, a couple notes about the study’s limitations are in order.

First, the response rate for the pre-race survey was rather low (26.6%). The authors indicate that the respondents did not differ substantially from non-respondents in terms of demographic data, but whenever a survey response rate is low, there is a possibility of unwanted bias.

Second, no information is available on the reasons for any athlete’s DNF. Clearly, it would be more informative if pre-race symptoms could be correlated with specific race-day medical problems that might cause the athlete to DNF.

In spite of those limitations, the investigators make some important observations in their running population, but these observations can probably be generalized to other athlete populations:

Nearly 1 in 5 athletes were “sick” in the days leading up to their race. This is a lot of participants.
The vast majority of “sick” athletes probably ignored warnings about participating until they were well (although certainly some may have felt better by race day).
Pre-race “sickness” with systemic symptoms was associated with a nearly doubled risk of DNF. That’s a big effect on performance, even if finer distinctions such as finishing times could not be discerned.

Thinking about the implications, athletes and their physicians should be aware of the potential negative consequences of racing when “sick.” Race organizers should consider distributing educational information about these negative consequences, while recognizing that athletes may not accept unwanted advice not to participate. Many factors (investment in training, scheduled time off from work, costs associated with the race/travel) may be barriers in athletes’ acceptance of such advice. Lastly, additional studies would be helpful if they examined: 1) race-day medical conditions and their relationship with pre-race symptoms; and 2) other measures of performance such as actual versus expected finishing times.

Reference:

Van Tonder A, Schwellnus M, Swanevelder S, Jordaan E, Derman W, Janse van Rensburg DC. A prospective cohort study of 7031 distance runners shows that 1 in 13 report systemic symptoms of acute illness in the 8-12 day period before a race, increasing their risk of not finishing the race 1.9 times for those runners who started the race: SAFER study IV. Br J Sports Med 2016; 50:939-945.

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The Medical Toll at Endurance Events

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.