Dr Larry Creswell
There is a great article about triathlon race safety in the Spring 2014 edition of USAT Magazine. The article shares strategies for athletes, event organizers, and USA Triathlon itself to help ensure everybody’s safety this triathlon season. This is must reading for the triathletes out there!
Download the USAT-Safety-Article.
The issue of “too much exercise” is in the news again this week. In last week’s edition of the medical journal, Heart, a group of German investigators headed by Dr. Ute Mons from the Division of Clinical Epidemiology and Aging Research at the German Cancer Research Center in Heidelberg reported on “A reverse J-shaped association of leisure time physical activity with prognosis in patients with stable coronary heart disease: evidence from a large cohort with repeated measurements.” This study extends our understanding of the importance of exercise in patients with known heart disease and the findings are very much worth noting.
In the popular press, this study received considerable attention in the past few days. In Forbes, we had a short article by Larry Husten, entitled “Exercise: Can There Be Too Much of a Good Thing?” In the Wall Street Journal, we had a short article by Kevin Helliker, entitled “Too Much Exercise May be Harmful to Your Health.” There were many other articles; these are representative. The headlines were all similar.
There was also interest in social media and the blogosphere. The research was shared along with admonitions about exercising too much, all in rather broad strokes.
Let’s take a look at the study….
The Study
Back in 1999-2000, just more than 1100 German individuals were enrolled in a longitudinal study. These were individuals who were undergoing inpatient cardiac rehabilitation (a monitored exercise program) after some sort of aucte heart problem–acute coronary syndrome, heart attack or myocardial infarction (MI), or coronary revascularization (with a stent or bypass surgery). As such, they were all known to have significant coronary artery disease (CAD). At the time of enrollment, they ranged in age from 30 to 70 years.
Over the following 10 years, these individuals answered questionnaires about their health at 1, 3, 4.5, 6, 8, and 10 years. At the time of the 1-year questionnaire, the median age of respondents was 61 years. The typical participant was male, overweight, a current or former smoker, with a history of heart attack, and high blood pressure. On each of the questionnaires, there was a question about physical activity:
“On average, how often have you engaged in physically strenuous and sweat-inducing activity in your leisure time in the past 12 months (ie, cycling, speedy hiking, gardening, sport)?”
And the possible answers included:
The respondents were also asked to estimate the number of hours per week, on average, they spent doing strenuous physical activity.
In addition to physical activity, the investigators collected information about the important outcome measures: major cardiovascular events (MI and stroke); cardiovascular mortality (death due to a heart-related cause); non-fatal cardiovascular events; and all-cause mortality.
The Results
At the time of the 1-year questionnaire, most individuals were physically active, with just 9.1% reporting “rarely or never” exercising. Most (41.3%) were in the “2-4 times per week” category. The “5-6 times per week” group accounted for 15.8% and the “daily” group accounted for 15.3%. For context, the current American Heart Association (AHA) guidelines on physical activity (generally, and not specific to patients with known CAD) call for 3 to 5 days of exercise per week, depending upon the intensity of the exercise. In terms of time, those guidelines suggest 150 minutes (2 1/2 hours) of moderate-intensity exercise OR 75 minutes of vigorous exercise per week.
Perhaps not surprisingly, as the individuals aged over the 10-year period of the study, their activity levels decreased. Perhaps their interest in well-being or focus on their heart condition waned as well. There was a relatively constant percentage of enrollees in the “2-4 times per week” category, but there was a decrease in those exercising more….and an increase in those exercising less.
Statistical analysis was used to try to isolate the influence of physical activity as a variable….and eliminate the influence of other confounding variables (employment status, smoking, obesity, self-reported “poor health,” history of MI, diabetes, high blood pressure, poor heart function, and number of coronary arteries that were diseased) as well as the influence of changes in the amount of exercise over time. Many of these confounding variables would otherwise have influenced the outcome measures.
The primary finding was that individuals who exercised the least (either “rarely or never” or “1-4 times per month) were at greatest risk for all 4 of the outcome measures. This isn’t surprising. This study confirms the findings of many previous studies.
The investigators also found that there was a sweet spot in terms of the frequency of exercise, where there was the greatest benefit, and lowest risk for the outcome measures. For all-cause mortality, cardiovascular mortality, and major cardiovascular events, the sweet spot was “2-4 times per week” of exercise. Either more or less exercise was associated with greater risk. For the outcome measure of non-fatal cardiovascular events, though, there was little association with the frequency of exercise. These results are the ones that received attention in the press this week.
On the face of it, though, these findings about frequency of exercise might be deceiving.
The investigators also reported on the amount of exercise–the number of hours spent per week in physical activity. Again, there appeared to be a sweet spot where the risk of the outcome measures was least: 10-11 hours per week, for all-cause mortality and cardiovascular mortality and ~9 hours per week for major cardiovascular events. In each of these cases, a broad range in the amount of exercise, perhaps 5 to 16 hours per week, conveyed a benefit over no exercise at all. And similar to their findings for the frequency of exercise, the investigators found very little relationship between the amount of exercise and the outcome measure of non-fatal cardiovascular events. I don’t recall seeing these results reported in the media.
Take Home Messages
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My column this month at Endurance Corner is about swim safety. Since the triathlon season is ramping up here in the U.S., I thought I’d post the column here, too.
From a safety perspective, the triathlon swim can be very unforgiving. As we know, there are a few athletes who die each year in the United States during the swim portion of multisport events. That’s really just the tip of the iceberg, though. Many other athletes require rescue because of serious medical problems or just because conditions on race day were too tough to handle.
Athletes often ask me: “What can I do to ensure my safety during the swim?” Here’s my 10-item checklist:
1. Get a check-up. Be sure that you’re healthy for the race. Visit the doctor for a check-up. Identify any major medical problems, especially any unsuspected heart condition. We know that among athlete fatalities, unrecognized heart problems are found in the majority.
2. Understand the warning signs. During training, pay attention to warning signs that may be a clue to an unrecognized heart problem: chest pain/discomfort, unusual shortness of breath, palpitations, light-headedness or passing out, and unexplained fatigue. Get evaluted if you have any of these symptoms.
3. Become a capable swimmer. Perhaps it’s obvious. This is the cornerstone to your swim safety on race day.
4. Practice open water swimming. It’s simply different from the pool. You need an extra set of practiced skills for the open water triathlon swim.
5. Choose an event carefully. Take into consideration your health and your preparedness. It’s find to “think big,” but remember to think about your safety, too. It’s easy to underestimate the demands of the open water triathlon swim.
6. Develop a race plan that takes your health and preparedness into consideration. Work with your doctor and your coach.
7. Check your swim gear before the race. Make certain your race suit, swimskin or wetsuit, goggles, and cap are ready to go on race day.
8. Include a swim warm-up as part of your pre-race routine. This will help with your safety as well as your performance.
9. Use a race-day checklist just before you start. Deliberately review the course conditions, recall your race plan, locate the safety resources, and make a conscious decision about whether to participate or not. Make a wise decision. Only you can make the final decision to participate.
10. Swim safely. Know where to find a lifeguard if you need one. Remember to stop at the first sign of a medical problem. Your life could depend on it.
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The news last Thursday was startling. Laurent Vidal, the 30-year-old French triathlete, reportedly suffered a “heart attack” and cardiac arrest during a swim training session. You may recall that Vidal is the star of the French triathlon team and finished 5th in the London Olympics. By report, he complained of chest pain and later collapsed in cardiac arrest. News accounts indicated that he was revived, regaining consciousness, and was transported to the hospital for further care. Follow-up reporting suggested that therapeutic hypothermia as well as induced coma had been employed in his treatment. Over the weekend there was very little reporting, though, at least in the English news media, so I don’t have any additional information about his condition to share here. On Monday came a Tweet from Vidal: “Hello world.” I’ll take that as a good sign and wish Laurent and his fiancé, fellow triathlete Andrea Hewitt, all the best during his recovery.
Interestingly, in a report this morning, came some additional information about Vidal’s medical history. We learned that Vidal had suffered from exertional syncope (blacking out while exercising) on two previous occasions and had undergone a detailed evaluation after the 2nd episode, in 2011. At that time he was given the diagnosis of neurocardiogenic syncope, a condition that was thought not to be serious. I’m sure these previous incidents will be given new consideration in light of Vidal’s cardiac arrest episode.
I can tell from the questions I’ve received about this incident that cardiac arrest remains somewhat of a mystery. Beyond cardiopulmonary resuscitation (CPR), and possibly the use of an automated external defibrillator (AED), most people don’t have much familiarity with the treatment of victims of cardiac arrest. Non-medical folks might go a lifetime and never witness such an event. I thought I’d use Vidal’s story as a starting point for a discussion about the treatment of victims of cardiac arrest.
Cardiac Arrest
We use the term “cardiac arrest” when an individual’s heart has stopped beating effectively. The victim loses consciousness and stops breathing. When this happens suddenly, without warning, we use the term “sudden cardiac arrest,” or SCA. The victim of SCA immediately appears lifeless.
Cardiac arrest is a different problem than “heart attack.” I’ve written a previous blog post on the terminology of cardiac arrest versus heart attack. In short, a heart attack occurs when there is complete blockage in one of the coronary arteries that brings blood flow and oxygen to the heart muscle. This condition typically produces chest pain. Affected patients are evaluated with coronary arteriography and undergo procedures like coronary stent placement or heart bypass surgery as treatments.
Cardiac arrest occurs because there is a sudden change in the normal electrical activity of the heart. There is a collection of abnormal heart rhythms, called arrhythmias, that can be responsible: ventricular fibrillation (VF), ventricular tachycardia (VT), asystole, or pulseless electrical activity (PEA). With each of these arrhythmias, the heart does not beat effectively and therefore does not pump any appreciable amount of blood. The blood pressure falls to zero and a pulse can no longer be felt.
Without treatment, the victim of SCA has died. The American Heart Association (AHA) suggests a conceptual framework called the “Chain of Survival” to outline the necessary links to increase the odds for survival:
Initial Treatment
If a victim of cardiac arrest is to become a survivor, there must be prompt and appropriate care at each step along the Chain of Survival.
It is important for bystanders to recognize the victim of cardiac arrest–unconscious, not breathing, no pulse. The initial treatment is CPR. In the United States, the AHA and American Red Cross offer classes in CPR. For people who are not healthcare workers, the AHA teaches chest compression-only CPR, instructing the rescuer to do chest compressions centered over the breastbone, or sternum, at a rate of 100 compressions per minute. The AHA teaches that the 100 compressions per minute rhythm can be maintained by doing the compressions to the beat of the 1983 Bee Gee’s hit song, “Staying Alive.” Healthcare workers are taught how to do rescue breathing interspersed between sets of chest compressions, either in 1- or 2-rescuer scenarios. If no nearby bystanders are trained in rescue breathing, then chest compressions alone are appropriate as an initial treatment.
While CPR is being performed, bystander rescuers need to notify the emergency medical system (EMS) to summon more advanced care for the victim. In the United States, bystanders can call 9-1-1 to alert the appropriate authorities. The telephone dispatcher will arrange for emergency medical technicians (EMTs) or paramedics to be dispatched to the scene. The dispatcher can also remain on the telephone to help provide guidance to the bystanders who are tending to the victim.
If there is an AED nearby, somebody should fetch it. These devices are often located in public spaces such as schools, shopping centers, fitness centers, etc. They may also be on hand for special events. The use of the AED is often taught in conjuction with the basic CPR course. Even without instruction, the AED is designed to “talk you through” how to use the device in an emergency situation. The AED is opened and the ON/OFF switch is turned ON. An electronic voice will provide instructions to attach defibrillator pads to the victim’s chest in 2 locations. The AED will analyze the victim’s heart rhythm and determine if a defibrillation shock would be helpful. Such a shock is helpful if the rhythm is VF or VT, but is not helpful if the rhythm is asystole or PEA. If needed, the AED will ask the rescuers to stand clear and it will deliver an appropriate shock, asking you to resume CPR if the shock does not terminate the arrhythmia. If the shock is successful, the AED will instruct the rescuers to just monitor the patient. If no shock is needed, the AED will instruct to continue CPR. The AED will continue to monitor the heart rhythm and work through this same algorithm repeatedly at several-minute intervals until EMS personnel arrive on the scene.
I mentioned at the outset that the survival rate for out-of-hospital cardiac arrest was poor. It’s encouraging, though, that in localities or situations where CPR training is widespread, the survival rate can be much higher. Interestingly, in a recent review of SCA at long-distance running events, the survival rate was reported at 29% and was attributed in large part to prompt CPR provided by bystanders.
Advanced Life Support
The next phase of care might best be called advanced cardiac life support (ACLS). This care is generally begun by EMTs or paramedics who were dispatched to the scene where a cardiac arrest victim is already receiving CPR by bystanders. Information about the circumstances leading to the victim’s collapse should be passed along to the medical professionals who respond. Sometimes there are very helpful details.
Away from the hospital setting, advanced life support is usually provided by EMTs or paramedics who have specialized training in this area. In the hospital setting, many employees–nurses, physicians, and others–can take classes offered by the AHA to become certified in ACLS. As a result, there may well be ACLS-trained bystanders when somebody suffers cardiac arrest.
Advanced life support will include both chest compressions as well as rescue breathing. Supplemental oxygen will be provided and breaths will be administered initially using a bag-valve mask. If the victim is not immediately revived, an oral or nasotracheal tube may be placed into the trachea (the windpipe) to continue to administer breaths to the victim. Electrode patches will be placed on the victim’s skin and an EKG monitor will be used to determine the heart rhythm. With CPR and rescue breathing in progress, the advanced cardiac life support phase of care is governed by algorithms that are specific to the exact type of heart rhythm. There are 2 primary algorithms–1 for VF/pulseless VT and another for asystole/PEA. In the hospital setting, we actually have hand-held cards with the algorithms to help guide a team of rescuers.
Included in the algorithms will be the use of medications, if needed, as well as defibrillation, if needed, depending upon the particular heart rhythm. CPR, rescue breathing, and the resuscitation algorithm is pursued while the victim is transported to the hospital.
Hospital Care
Efforts at resuscitation continue until either the victim’s normal heart rhythm is restored or the team of caregivers concludes that further efforts will be fruitless. There is no absolute convention about how long resuscitative efforts should be continued, but there are certainly examples of patients who are successfully resuscitated after prolonged CPR. As just one example, I’ve written here at the blog about the soccer player, Fabrice Muamba, who was revived after 78 minutes of CPR.
If a victim’s heart rhythm is restored, then there are 2 major immediate goals: 1) prevent a recurrence of the near-fatal arrhythmia and 2) protect the body’s organs, as much as possible, from the effects of the disturbed circulation while the resuscitation efforts were being made. Efforts at the first goal will depend upon the known, or suspected, cause. Evaluation and monitoring is conducted to be certain that the blood oxygen levels and blood electrolyte levels are appropriate. Often, anti-arrhythmic medications will be used for this purpose. The second goal is also very important. We know that, even with CPR that is successful and results in revival of the patient, there can be insufficient blood supply to the body’s organs for a period of time. The brain is particularly susceptible to injury because of inadequate blood floow or oxygen, even for relatively short periods of time. One technique that has gained popularity in recent years is the use of induced coma combined with hypothermia (lowering the body temperature by several degrees) to reduce the metabolic demands on the brain for a period of about 48 hours. This allows potentially better recovery of the brain. We know that such an approach may improve the neurologic outcomes for at least some patients who have suffered cardiac arrest. This technique appears to have been used in the case of Laurent Vidal.
The last issue is to determine what caused the cardiac arrest. There’s actually a fairly long list of possible causes. In the sports setting, for younger athletes the most likely heart-related causes are hypertrophic cardiomyopathy (HCM)–an inherited disorder of the heart muscle; a coronary artery anomaly–an artery that developed abnormally during development; an inherited cardiac ion channel abnormality (eg, long QT syndrome); or arrhythmogenic right ventricular cardiomyopathy (ARVC)–another inherited disorder of the heart muscle. But sometimes cardiac arrest may be have a non-cardiac cause like pulmonary embolism or stroke. Even a sharp blow to the chest can produce cardiac arrest, a situation called “comotio cordis.” The evaluation of survivors of cardiac arrest is done in a systematic way to sort through the various possibilities. It’s usually possible to determine a cause, but there’s a small chance that no cause is found.
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In Part 3 of my short series on heart rate variability (HRV), my column at Endurance Corner discusses the hardware and software tools that are currently available to athletes who want to use HRV metrics in their training.