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Did I just Bonk...or was it someting else

Larry P Wasser | Published on 5/16/2020

The Outer Line: ‘Did I Just Bonk?’ — signals no cyclist should ignore


There are some signals which might suggest that you should take a more serious look at your health, rather than simply “soldiering on” in silence.


May 6, 2020 Steve Maxwell, Dr. William Apollo


Endurance athletes are known for overcoming adversity, often suffering in silence while en route to glory, or sometimes just trying to finish an event. But every cyclist, from the Saturday morning enthusiast to the top-level pro racer, can recall at least a few times when they simply weren’t able to overcome that adversity, when they simply ran out of energy and the courage to keep going – in short, when they “bonked.” This common experience unites all cyclists – and across all levels of skill. For cyclists, it is a fact of life, but it is also a part of the comradery and allure of cycling. We all have our bonking stories.


Most cyclists are pretty well in tune with their bodies and have a better-than-average understanding of sports physiology. Many are quite adept at processing and understanding the myriad data collected from watches, heart monitors, power meters, and the like. But despite this sophistication, there is often some degree of trepidation – especially among master’s athletes – about their ability to accurately differentiate between just having a rough day on the bike versus a situation that may require further medical evaluation.

One of the common questions asked by cyclists to their doctor is – “Is there anything I should look for while riding to suggest that I might be having a heart problem?” And that question is often followed by, “And what, exactly, is a silent heart attack?” Both questions betray a level of concern. And the answers to these questions are not always straightforward. However, there are some signals which might suggest that you should take a more serious look at your health, rather than simply “soldiering on” in silence, and we will take a look at these below.

“I Just Didn’t Feel Well…”

All serious and competitive cyclists are familiar with “hitting the wall,” or “bonking” – that sensation of sudden and overwhelming weakness and fatigue that is typically caused by dehydration and/or depletion of energy stores from the muscles and liver. That effect is basically the endurance athlete’s kryptonite – when it hits us, we are toast. We all know that the best treatment strategy is to actually avoid bonking in the first place – by eating, hydrating, and resting appropriately. But nevertheless, we all forget and sometimes fall prey to this trap; even top-level pros often blame poor performance on failing to eat or drink enough during a race.

But what should you do if you feel really poorly during a ride, perhaps experiencing symptoms which are more extreme than usual or even totally different from anything you have experienced before for the same level of effort? The word “really” is the operative phrase here, but it is important to try to define for yourself what feels typical or normal versus what feels abnormal during a ride, since ultimately you are the best judge in discriminating between the two. The important question here is: can more serious heart problems be misconstrued as simple bonking? And how can you tell the difference? Some real-world examples can help us better understand these distinctions.


A veteran rider, who is had thousands of good days in the saddle as well as a few bad ones, was out on a group ride with the local club. But during this particular ride he just did not feel well. As the ride went on, he recognized that he definitely felt a little different than he ever had before, and he wisely decided to stop turning the cranks, and pull off to the side of the road to assess the situation. Fortunately, a retired nurse practitioner was riding directly behind him, and she turned out to be his savior. They had known each other for years, and she agreed that he did not look too well. They decided to call 911 for assistance. Long story short, he was later diagnosed in the emergency room with a small heart attack. Fortunately, this story ended happily because both riders could recognize that something was clearly “different” that day. More importantly, they promptly acted upon their suspicions. Based on years of aggregate riding experience, both realized that this was more than just a simple case of dehydration or inadequate nutrition. His symptoms were different from anything he had experienced before while riding.


Many people – not just cyclists – are curious, even concerned about the possibility of sustaining a “silent” heart attack. The diagnosis certainly sounds sinister. Some trusted sources would even lead us to believe that silent heart attacks may comprise up to 45 percent of all heart attacks – which seems like an alarmingly high percentage to the casual observer. But this does not mean that people are walking around in blissful ignorance, having heart attacks all the time, totally unaware of what is happening. By definition, a silent heart attack is an event that lacks the intensity of a “classic” heart attack – the type of symptoms that stop you in your tracks and cause you to call an ambulance, and probably landing you in emergency surgery to have a blocked vessel opened.

In sharp contrast, during a silent heart attack, the so-called “classic” symptoms of chest pain, arm pain, neck/jaw discomfort, shortness of breath, lightheadedness, and sweating – generally unmistakable signs of a heart problem – are much milder. They are often downplayed and are typically – and dangerously – misinterpreted as being caused by less serious non-cardiac illnesses. In a sense, a silent heart attack is somewhat of a misnomer, since retrospective reviews show that most cases were really not “silent” events at all, but rather misinterpretation of symptoms by either the patient, the health care provider, or both – ultimately resulting in a delayed diagnosis. These are essentially warnings that should not go unnoticed or unattended.

For example, maybe that unusually severe episode of indigestion you suffered two weeks ago – which was not responsive to your normal antacid therapy – wasn’t really related to your stomach at all, but rather angina, or chest pain related to your “missed” heart attack. The important point to remember in these situations is that anyone can experience a bonk while riding, but if you really feel poorly, and especially if any of the above symptoms are also present, you should stop riding immediately and seek medical attention. Again, that word “really.” But once more, if you experience symptoms that are more profound than usual or foreign to anything you have experienced before, it should definitely raise a red flag.

This ability to effectively recognize what is different from your normal situation or feeling could turn out to be lifesaving. Athletes who should be particularly attentive are those who have a personal or family history of heart problems, or other health problems such as tobacco abuse, diabetes, high blood pressure, or cholesterol problems – all conditions considered to be typical cardiac risk factors. Also, women should be particularly vigilant here, since traditional wisdom has suggested that they are less likely to experience “classic” heart attack symptoms than men. But as with men, the most common heart attack symptom in women is also chest pain, but women more commonly experience other symptoms like shortness of breath, nausea/vomiting, and back or jaw pain.


Endurance Athletes: Their Own Worst Enemy?

Runners, cyclists, and multi-sport athletes, by virtue of their competitive nature, often tend to miss or ignore more subtle clues about their own health, resulting in delays in diagnosing important underlying problems. For example, most cyclists have experienced the physiologic strains associated with riding “full-gas.” Whether sprinting for the city line against your friends on Tuesday night, or climbing Alpe d’Huez during the Tour de France, the feeling is the same: breathlessness, burning legs, breathlessness, fatigue, breathlessness, elevated heart rate, and so on. How much do I have left before the engine blows?

Our ability, and perhaps more importantly our willingness, to persist during these intense efforts – when many people would just stop – can often be the difference between winning and losing. When endurance athletes begin to lose their competitive edge, they usually assume a deficit in training as the cause of their decreased performance. Increase the training volume; discuss things with your coach and streamline the workouts. Problem solved, right? Well, not always.

Consider the example of a successful young NCAA cross-country runner who suddenly found himself struggling with a reduced performance level which he could not understand. His competitive drive was intense, and he never entered a race that he didn’t try to win, yet he was having difficulty maintaining his typical pace, and despite increased training volumes, he continued to be relegated to slower groups during practices. Frustrated, he explored all avenues, working on his form with running coaches, and even seeing a sports psychologist regarding “positive visualization.”

He eventually consulted a cardiologist – because of persistent breathlessness, and a single episode of chest pain which occurred during an 800-meter event. It is probably a fair assumption that most cross-country runners have been breathless at some point during a race, learning to push through the discomfort in hopes of standing on the podium. Given this athlete’s relatively young age, it seemed much less likely – but not impossible – that there was something serious going on. But in this instance, his symptoms were also associated with an unexplained decline in performance. Therefore, it required a much closer look.


He was eventually diagnosed with hypertrophic cardiomyopathy, the most common cause of sudden death in young athletes under the age of 35. There are two important lessons to be learned here. Certain symptoms should always be investigated in an athlete, including but not necessarily limited to chest pain, shortness of breath, racing heart (palpitations), and passing out. All of these symptoms may represent serious underlying heart problems. In this case, persistent breathlessness and chest discomfort were important clues pointing to the correct diagnosis, yet they were initially glossed over. Equally important to recognize was this runner’s unexplained decrease in athletic performance, initially attributed to a training deficit, which failed to improve despite increased training volume and refinement of his workout routine.

Another illustrative example involves a middle-aged health care worker and avid distance runner, whose idea of a “moderate” run was a 7-minute-per-mile pace. For several weeks, he noticed difficulty in completing his treadmill workouts, because of unusual fatigue, but sometimes because of chest pain as well. He eventually sought medical advice after briefly passing out on the treadmill and was taken to the emergency room. He was diagnosed with coronary artery disease, the most common cause of sudden death in athletes over the age 35 and required a stent to open a serious blockage on the front of his heart involving the “widow-maker” vessel. Fortunately, this story also ended well, despite the fact that multiple clues were ignored – including two “classic” cardiac symptoms (chest pain and passing out) as well as an unexplained reduction in athletic performance, which actually preceded his missed symptoms.

Don’t Be an Ostrich

The British writer C.S. Lewis once observed that “denial is the shock absorber for the soul. It protects us until we are equipped to cope with reality.” Unfortunately, it seems like this sometimes characterizes endurance athletes. It is often psychologically hard for strong and superbly fit athletes to realize and to admit that they may actually have a problem and seek help – rather than playing the mental game of pushing through pain.

Retired mountain bike racer Mark Weir’s candid story is very compelling and illustrates just how difficult it can be for some people to overcome this hurdle. The “tough guy” of mountain biking describes how he navigated a sea of confusing and sometimes misinterpreted symptoms before finally admitting to himself that something was actually wrong. He describes the multifaceted psychological debate which ensued, where he analyzed all of the possible consequences to both himself and those around him, prior to seeking medical attention and ultimately being treated for coronary artery disease.

The best advice is to learn how to carefully listen to what your body is telling you, and then to be honest with yourself. If you have been riding for a long time, you probably have a pretty good general sense of how your body feels and reacts to certain situations while training or competing. Recognizing some of the more classic cardiological symptoms, as well as the more subtle changes from our predictable fitness and training baselines, are often the key to identifying important problems. When something feels a little out of whack, it is probably good to get it checked out, particularly if you are older. What is there to lose? Remember the lessons learned by the people just discussed – all seemingly healthy endurance athletes, just like you – to avoid some of the common pitfalls which could derail your own health. In other words, do not always assume that it was just a bonk.

Dr. Bill Apollo, an amateur bike racer, runner, and duathlete is a Harrisburg, Pennsylvania-based cardiologist, and medical director of the UPMC Pinnacle Sports Cardiology Clinic.