Thursday, September 8, 2011

Death by Exercise, Marathon, Triathlon

Sudden cardiac death – as in the college-age basketball player or the hyper-fit triathlon participant – tends to make the news. As it should. Newsworthy death while exercising provides every non-exerciser with rationale for not exercising. “See” they say, “this person was an avid runner [cyclist, swimmer] and dropped dead at 40.” The contrarian point being that the endurance sports that are supposed to protect against heart disease sometimes appear to do just the opposite.

There is an iota of truth to this observation. Estimates are that just under one person per 100,000 participating in a half-marathon or marathon, or 1.5/100,000 participating in a triathlon race will die during or immediately after the event. The great majority of triathlon deaths occur in the swim phase. Figure a collective three million participants in these types of races each year and that comes to maybe 30 deaths per year. There are fuzzier estimates of perhaps one sudden death per every million exercise event for other forms of exercise. So the true answer is yes, exercise can kill the physically fit, but no, not a risk factor worth avoiding exercise entirely.

There is more truth in the observation that exertion by the physically unfit can result in fatal cardiovascular events. The classic case is the middle-aged office worker who drops dead shoveling snow while attempting to clear the driveway and get to work. Contributing factors include the fact that blood pressure peaks in the morning a few hours after waking up, and the fact that exertion in cold weather constricts arteries, further adding to heart stress (triathlon deaths in cold water probably for the same reason). Snow removal related heart attacks frequently occur in women and men with no known pre-existing heart disease.

Exercise can also result in accidental death. In the U.S., walking, running, bicycling, swimming, boating and winter sports add up to about 10,000 deaths per year. Subtract half who are either children or are adults under the influence of alcohol (as in walking or riding a bike home from a bar, at night), and it’s still a big number. But the total pales compared to the 2,500,000 total deaths per year, of which many are premature cardiovascular deaths brought on by a lifetime of inactivity.

The good news is that benefits from even modest amounts of exercise are becoming clearer. In a 2011 article in The Lancet, C.P. Wen and co-authors reported that for a multi-year tracking study of 416,175 Taiwanese adults, as little as 90 minutes per week of moderate-intensity exercise reduced the risk of death by fourteen percent. Each additional 90 minutes per week added four percent further reduction. Other studies have also reported the greatest improvement for modest exercise compared to no exercise at all, and diminishing returns for progressively more exercise.

The theory that over-doing exercise may cause more harm than good has neither been confirmed nor disproven. A science journal article by Masaru Teramoto reviewed fourteen studies of longevity of elite athletes. Athletes from endurance sports had 3-6 year longer life spans than the general population, but the results were mixed for athletes in power sports. The latter may be disadvantaged by larger body size typical of their sport or from a discontinuation of exercise as they age. The authors caution that elite athletes may by genetically different from the population as a whole, with both their abilities and lifespan being consequences of their genes rather than one causing the other.

There is a non-fatal problem with exercise – it is potentially addictive. As one well-known fitness expert author put it, “…people reduce their lives to fitness routines, training as many as 40 hours a week. That the effort may wreck marriages and compromise immune systems isn’t even relevant. To these people – demographically a diverse lot – exercise is addictive. The more the body gets, the more it wants. In return, the drug of exercise infuses the swimmer, cyclist and runner with two powerful illusions: that he/she is escaping the horrible, and progressing toward the divine.”

Beyond the story: Exercise-related articles on this blog include "Avoiding Overhydration" (Feb 2010), "Hypothermia" (Nov 2010) and "Recovery from Donating Blood" (March 2011). For a detailed, referenced take on death from exercise, go to the entry "Sudden Death and Exercise", in the Encyclopedia of Sports Medicine and Science:


  1. One of the factors that cause this is improper choice of gym clothes. Too tight or too loose can spell the difference in the individual's difficulty or ease in completing the race. Too tight will cut off circulation and too loose will increase the needed effort to swim or run as the loose clothing will either catch air or water when swimming, thus adding to the weight of the individual.

  2. Florence - that did not come up in any of my research on risk of death. Obviously, the wrong type of clothing can affect performance, but shy of a lead-lined bathing suit I cannot imagine that bad fashion sense might kill someone.