Technical FAQ: Heart arrhythmias, flying with discs

This week, Lennard Zinn address questions about heart problems and flying with disc brake-equipped bikes.

Follow-up on heart arrhythmias

Dear Lennard,
I think you should share medical advice with caution. Routine echocardiography for a large asymptomatic population is not indicated for screening for “safety.”

Even cardiac stress tests will not predict with any confidence when a patient might have a plaque rupture and die of a huge heart attack (think of former NBC News anchor Tim Russert, who had a nuclear test one month before dying suddenly).

More sage advice would be that anyone who has been sedentary and who wants to go into more serious training should see a health professional for advice, especially those entering middle age. A medical professional can gauge appropriate tests based on the patient’s risks for certain health issues.

For example, the single most common risk factor of sudden death in marathoners is a prior history of smoking and sedentary living.
— Prospero Gogo, MD
Associate Professor of Medicine
University of Vermont Medical Center
Director, Cardiac Catheterization Lab

Dear Prospero,
Thank you so much for your letter. As you said, the best advice is always to see a doctor and follow his or her recommendations. I should not have given a blanket answer for something as individual as human health.

Dear Lennard,
In regards to your reply to Steve about cardiac testing, I have a follow-up question.

I took up cycling nearly 20 years ago and have been an avid cyclist during that time. A couple of years ago I found myself having difficulty keeping up with my long-time group, despite the same or more training. My doc recommended a cardiac stress test and echo-cardiogram. The stress test went fine (and I felt highly complimented by the doc who referred to me as a “high level athlete” in the test results). The echo-cardiogram, however, revealed that I had left ventricular hypertrophy (LVH). Unfortunately, the doc did not know how this could affect my cycling, or if I was in any mortal danger. Apparently, there had not been any comprehensive studies analyzing the risks of athletic activity for somebody with LVH, or at least none up to that time. He put me on meds to lower my blood pressure and that was that.

Since that time, a couple of injuries forced me off the bike for the last couple of years, but I’ve recently taken back up a regular schedule of cycling.

I’ve ordered your book “The Haywire Heart” but was wondering if you were aware of any other research that has been done specific to LVH and its associated risks. Do I need to be worried? Or can I go out and train with the same high intensity that I used to?
— Mark

Dear Mark,
By now maybe you’ve read “The Haywire Heart” and already know what I’m going to tell you. First of all, you ought to seek the advice of a cardiologist who deals with lots of athletes.

You will also have seen in the book that in a masters athlete, hypertrophy of the heart can lead to scarring in the heart, and myocardial scarring is a substrate for arrhythmia. A key finding of a Scottish study of masters athletes that we detail in the book is that fibrosis markers were higher in masters athletes, with more hypertrophy leading to higher levels of collagen chemicals, which are related to fibrosis (scarring).

I don’t think anybody can predict whether you would end up with heart arrhythmia or other problems if you were to go back to training with the same intensity that you used to. What I think can be said from related medical studies is that, assuming you are a “veteran” or “masters” (over 40-year-old) athlete, your left ventricular hypertrophy (LVH) increases the likelihood of developing an arrhythmia than if you did not have LVH, and that this risk goes up with increased demand on the heart through hard training. And whether it is high intensity, high volume, or both that most increases that risk from endurance training, I know of no study that separates those.

Two Scandinavian studies of cross-country skiers that we discuss in the book do not make that distinction. In one study, 509 non-elite 65- to 90-year-old male competitors in the mountainous, 54-kilometer Norwegian Birkebeiner cross-country ski race had 1.9 times the incidence of AF (“atrial fibrillation,” the most common cardiac arrhythmia) than did 1,768 men in the same age group from the general population. And in a bigger study less skewed toward elderly athletes, 52,000 finishers of the Swedish Vasaloppet 90km cross-country ski race followed over a 10-year period showed that both volume and speed increase the risk. Competitors who had completed the Vasaloppet five times were 29 percent more likely to have AF than those who had completed the race only once. And skiers in the fastest group were 30 percent more likely to have developed AF than skiers in the slowest group.

Training for marathon ski races certainly involves lots of volume, and training to be one of the fastest skiers, in my experience over 22 years of cross-country ski racing that includes participating in both of those Scandinavian races, always requires quite a bit of high-intensity work as well. So these studies don’t separate out risks of training intensity from training volume. That is as thorough an answer as I can give you to your questions of whether you “need to be worried” if you “go out and train with the same high intensity” that you used to.
― Lennard

Dear Lennard,
I always enjoy your articles, but the recent one on cyclists preparing going to the doctor with cardiac issue was especially interesting to me, as I’ve had a different but related experience. And, I’m pleased to see articles on this area, as cyclists need to watch out. I’ll try to be brief.

I’m 63 years old and have been back to cycling for about a dozen years. I’m an enthusiast, mostly ride solo, and I’m not very competitive. For a few summers I went on a couple of weekend 100km to 180km per day tours, and would ride around 200km per week. 

Things had been steadily improving over the years, and then things got harder one summer, and I had recovery problems while training in the fall and winter. I always ride with a heart rate monitor (sometimes with power too), and detect recovery issues by a lower-than-expected heart rate during a warmup. That winter, there were more times than usual when I was not able to do my normal day-on, day-off schedule because my heart rate indicated I was not adequately recovered. When the spring came, I started back into longer rides and some intervals. One was going up a gentle but steady hill for about 5 minutes near threshold. When I did it, there was a gentle ache on my left side, nothing special. One repeat and I decided to go home and take a few days off. Repeat, and had the same symptom.

I got an appointment at my GP’s clinic quickly and went through the story with the doctor. I was into a great cardiac center the next Wednesday, and had two stents put in in July.

 It turns out I had the same thing my mother had many years ago when she was my age, plaque buildup in two of the arteries feeding the heart. Not too serious for me at that point, and I probably would not have known for years if I had not been cycling. And, if it had been noticed, I still might not have had the stents put in if I had not been so active. However, if I had not listened to my body, who knows what might have happened one day when I’m out alone on the road.

I’ve recovered well and have been back on the road for a couple of years.
— Jim

Feedback on flying with disc brakes

Dear Lennard,
Your advice in this FAQ included the passage, “… In any case (pun intended), I recommend that you remove the rotors from the wheels for travel. That makes the obvious case (pun intended again) for CenterLock rotors and hubs, rather than 6-bolt ones, so you are spending more time riding and less time screwing around with a dozen rotor bolts.”

Shimano CenterLock rotors have a very high torque recommendation (40Nms or so). I would love your advice as to:

— Recommended torque wrench covering this range (for home use).

— How this can be accomplished by the traveling cyclist.
— Peter

Dear Peter,
To tighten a cassette lockring or a CenterLock rotor lockring to torque, you use a 26mm socket on a cassette lockring tool. While 26mm may not be a common size, it is the same size as some suspension-fork top caps. As for what torque wrench to use, you want at least a 3/8”-drive one (1/2”-drive is also fine) that is rated to at least 60N-m and has a long handle. Here is an example.

When traveling, you’re just going to have to tighten it down with a Crescent wrench to your best guess on the torque, unless you want to lug along a big torque wrench.
― Lennard

Dear Lennard,
Regarding the fellow who had a bike that required fork removal for transport (Flying with discs) but had an internal front brake hose — would a hydraulic quick-connect (or perhaps two) work for him? Here is an example.
— Steve

Dear Steve,
I haven’t heard more about that Formula quick hydraulic coupler since its announcement four years ago. I’m not sure it’s still available and whether there are any problems with using it with a mineral-oil system vs. a DOT-fluid system.

There are lots of quick-disconnect couplers for automotive and agricultural applications. I know there will be a demand for them for bicycles, now that disc brakes on road bikes are becoming ubiquitous.

As another reader named Tom pointed out, TRP is developing one, but it’s not up on TRP’s site yet. TRP’s marketing director Lance Larrabee said, “Quick connect hose kits will be available before the end of the year. Price TBD. Currently our hose O.D. is 5.5mm. I believe Shimano is 5.0MM, so it wouldn’t work [on Shimano brakes].”
― Lennard