Monday, October 29, 2012

Endurance Sports and Heart Health (Part I): Are Triathlons Dangerous?

This is the first part in a series of posts on endurance sports and heart health. 

About a year ago I decided to make the jump into triathlon. After playing soccer my entire life, including in college, I took up running as a way to fill the competitive void left. I was always one of the most fit players, often finding a sense of enjoyment from strength and conditioning sessions. I drew my enjoyment from others' dread.

300 yard shuttles or 1-mile intervals on the track- let's do it. Agility ladder - I'll go faster and harder than you can. Squats, deadlifts, and box jumps - sounds like a fun off-season to me.

Soccer introduced me to the methodical - and sometimes regimented - approach to training. Finding my own weaknesses and then relentlessly working to improve them. When it came to conditioning and fitness drills, I always wanted to go longer, faster, and harder than anyone else. More was always better.

So when it came time to step away from soccer, I needed something where I could try and go longer, faster and harder. Distance running seemed like a great fit and in 2007 I trained for and completed the Philadelphia Marathon. My training approach was what I had come to know - more was always better. I logged a lot of miles.

Today my training approach quite different - more is better up to a point; quality always trumps quantity; and recovery is the most important part of training.

So what happened?

It wasn't until a couple years ago when I began to understand some of the serious health risks of endurance sports. Research continued to emerge looking at the effects of excessive and long-term exercise on the heart, and particularly the cardiac remodeling that takes place as a result of years of running, biking or other aerobic activities. One major effect is something called hypertrophic cardiomyopathy - essentially a thickening of some parts of the heart muscle, which in turn makes it harder for blood to leave the heart. The heart must work harder. So, during an endurance event, when the demands of the heart are high, if an individual suffers from hypertrophic cardiomyopathy (or if their heart has remodelled after years of endurance exercise and stress), there is a risk of adverse cardiac events, like cardiac arrest, which result from blood vessel constriction. This article is a great overview.

Marathons and triathlons demand a lot of the heart, both over time and in short bursts. In triathlons, for example, the heart must quickly adjust when the body starts swimming from a virtual stand-still, often at a demanding pace and sometimes amongst some 2,000 other swimmings (watch the swim-start of Ironman Hawaii if you want a visual of how this looks). 

Stories about sudden cardiac events in marathoners and triathletes continue to make headlines. "Runner dies near finish of Chicago Marathon." "Shadows Over Ironman, but a Spirit of Carrying On." "Ironman death stuns athletes." With a seemingly increasing prevalence of such events, more research is now going into the issue, including by USA Triathlon.

USA Triathlon Fatalities Incidents Study 

To the credit of USA Triathlon - the national governing body for the sport in the U.S. - they recently commissioned a Medical Review Panel study to look at deaths during USAT-sanctioned events from 2003 to 2011. Preliminary findings were shared with a review panel in January of this year and the final report was published on the USAT website last week. Regardless of the study's limitations (some I discuss below), it has certainly generated a fair bit of discussion within the triathlon community.

Between 2006 and 2011, the study found an average of one death per every 76,000 participants, or about 1.4 per every 100,000 participants. For comparability, a study published earlier this year in the prestigious New England Journal of Medicine found roughly 1.25 cardiac arrests per every 100,000 participants in marathons and half-marathons held in the U.S.

Here are a few conclusions that can be drawn: 
  • The number of USAT-sanctioned events, number of members and participation in USAT-sanctioned events have all steadily increased over the past several years. 
  • The study didn't show any particular trends related to overall number of fatalities or fatalities per 100,000 participants.
  • The majority of fatalities occurred during the swim portion of the triathlon (31 of the 45 total), and in varied race lengths, swim venues (e.g., ocean vs. lake), or method of swim start (e.g., mass start, wave, or time trial). Cardiac arrest was described as the immediate cause of death.
  • The largest number of fatalities occurred in participants ages 40-49, with the 50-59 age group in a close second.
Summary of USAT Events, Participation and Fatalities


A few things the study did not show: 
  • The study didn't exclusively look at USAT-sactioned adult triathlon races, but rather, it also included a variety of other activities sanctioned by USAT, such as camps, clinics, or short youth events. Nonetheless, the number of fatalities is still relatively small and there doesn't appear to any increasing trends. The perception of an increasing trend might simply be due to increased media coverage of the sport.
  • The study didn't include all entrants. Instead, participation numbers do not include the number of individuals who dropped out of races without finishing. If the study considered all entrants, the prevalence of fatalities would have been even lower.
  • Lastly, and most importantly, the study says nothing about context of the fatalities. What was the temperature of the water? What were the weather conditions? Did the athlete use a wetsuit? What were the medical resources available at the event? How experienced were the athletes who died? What was their medical history? 
Many of these contextual pieces of information could help draw far more useful conclusions about the reason for the fatalities. Most fatalities occurred in athletes of middle age (40s and 50s), were they life-long endurance athletes who maybe were experiencing the type of cardiac remodeling discussed above, which increases risk for sudden cardiac events (cardiac arrest was described as the immediate cause of death in 31 of the deaths)? Was their life filled with the added stresses of work, kids, the economy, etc., which puts additional strain on the heart?

Despite leaving a variety of gaps and drawing only minimal conclusions (a critique of some who say USAT was simply covering their bases to avoid claims of negligence rather than trying to draw any meaningful conclusions), the study does add to the overall conversation about addressing sudden cardiac events in endurance athletes. There is still a lot to learn. Post your comments below.

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