Human Limits

Exploring performance and health with Michael J. Joyner, M.D.

Photo of Michael J. Joyner, M.D.

Fitness & Mortality Update

Two recent scientific papers make it time for a quick update on the topic of fitness and mortality.


1.  Fitness vs. Cancer Mortality

The first paper is meta-analysis that summarizes the results of a number of studies on the relationship between fitness and cancer mortality. The results were pretty striking:


“Six prospective studies with an overall number of 71 654 individuals and 2002 cases of total cancer mortality were included. The median follow-up time in the studies was 16.4 years. Cardiorespiratory fitness showed a strong, graded, inverse association with total cancer mortality. Using low cardiorespiratory fitness as the reference group, intermediate and high levels of cardiorespiratory fitness were related to statistically significant decreased summary relative risks (RRs) of total cancer mortality of 0.80 [95% confidence interval (CI) 0.67-0.97] and 0.55 (95% CI 0.47-0.65), respectively. Studies that adjusted for adiposity yielded similar results to those that did not adjust for adiposity.”


This means that folks with high cardiorespiratory fitness have about half the risk of death from cancer as people in the low fit group.   Usually, in these types of population studies “high fit” is defined as the ability to do “10 mets” of exercise. For example a person with a 10 met exercise capacity can typically run 6 miles (10 km) per hour for few minutes at the end of a maximum exercise test.   This is also an exercise capacity that many if not most middle aged people can attain if they watch their weight and workout regularly.   So while physical activity and cardiorespiratory fitness are not the same thing, many active middle aged people can get to 10 mets. The flip side of this relationship is that most highly fit people are also pretty active and they do at least some higher intensity exercise training which makes it likely they have a 10 met exercise capacity.


2.  Fitness vs. Cardiovascular mortality

It has been known for a long time that increased fitness is associated with both lower all-cause mortality and lower cardiovascular mortality. A remaining question is whether this relationship flattens out at about 10 mets. In other words do people who can do more than 10 mets have even lower mortality? The graph below comes from a short report on this topic in almost 70,000 people (64% men) followed for about 12 years including about 38,000 with an exercise capacity of greater than 10 mets. The top panel shows that very high fitness was associated with lower mortality in all age groups. The bottom panel shows the dose response relationships between fitness for the entire study population.   So greater fitness equals lower mortality.





Evidence for the protective effects of fitness and its close relative physical activity keeps piling up.   The cancer data is especially heartening, and that fact that things don’t flatten out for fitness vs. mortality at very high levels of fitness is perhaps another piece of objective evidence against the too much exercise “hypothesis”.



Faster, Older, Younger?

It has been a while since I did a post with a hardcore “human limits” angle, but some impressive middle and long distance running results over the last couple of weeks make the time ripe for a few observations. So, here goes!


Is 45 the new 35?

In mid-February the 40 year old and seemingly ageless Bernard Lagat went 3:54.91 for the mile at the Millrose game in New York City.   The previous best time for a 40+ was 3:58.15 by Eamonn Coghlan – the “Chairman of the Boards” set in 1994.   Lagat went 3:51:38 at age 36 and his best mile time is 3:47:28 at age 26. Who knows just how fast he could go if he focused on the mile and ran five or ten highly competitive races in the next several years. My bet is that he could run at least a couple of seconds faster.


I also bet that if Lagat continues to train for the next five years, he might be able break 4 minutes in his middle 40s.   If top competitors can avoid injury and keep training hard, it is possible for them to maintain their fitness at a level near the peak values typically seen in their 20s. However, even the most dedicated and injury free trainers start to lose something in their 40s. The minimal rate of loss for maximum oxygen uptake is probably about 4% from age 40 to 50, and this is a key determinant of mile time.


So if Lagat lost only 2% in the next 5 years that would slow his mile time by about 5 seconds and his projected age group record at 45 would be 3:58 to 3:59. The old timers reading this will remember that in the early 1970s four-time Olympian George Young broke 4 minutes in his middle 30s. At the time that seemed both inconceivable and unbelievable.


I wonder if and when we will see a sub 4 minute mile by a 50 year old?


Chasing Paula

The world record for the women’s marathon is 2:15:25, set by Paula Radcliffe who also owns the two next fastest times and no one else has broken 2:18. Her marks are true outliers and a number of people wonder if and when the field will “catch up”.   On February 16, Florence Kiplagat ran the half-marathon in 1:05:09 which converts to an estimated marathon time of just less than 2:16. A few days later Genzebe Dibaba went 14:18:86 for 5,000m. That time is equal to about a 2:17 marathon.


The chart below is from an analysis that Sandra Hunter, Andy Jones, and I did on the 2-hour marathon “equivalent” for women. It shows the 100 top men and women’s times as a % of the world record with and without Radcliffe’s times. Based on these recent times at shorter distances, perhaps the men’s and women’s curves might start to look similar as more women run times between 2:15 and 2:18 in the next few years.






That having been said, it will be interesting to see if Paula Radcliffe holds the three fastest marathon times for women in five years. My bet is no.


Young Guns!

Last week Tim Kruse who worked in my lab prior to starting med-school at the University of Washington sent me an e-mail pointing out that about 20 collegiate male runners broke 4 minutes for the mile in February. In response I asked where these guys came from and he drilled down on it a bit and said that 13 came from the U.S. and several more from Canada.

The question then became why? Better training? A bigger talent pool? Better tracks? Doping? I bounced these ideas off David Epstein, Alex Hutchinson, Amby Burfoot and Rickey Carter. The general consensus was that doping was not a major issue. Better tracks and better competitive opportunities likely played a role.   However, several people commented on the role internet and dedicated track and distance running sites. These sites (like LetsRun) promote the sport in general and are also a great forum to share information about training and also inspirational stories. My guess is that they have been catalytic.

Amby pointed to an article he wrote a few years ago about the “turning point” in U.S. distance running being marked by the 2000 Foot Locker High-School Cross-Country Championships which featured Alan Webb, Dathan Ritzenhein and Ryan Hall. Evidently these guys had been more or less stalking each other for some time via an early internet site devoted to high school running. Amby’s article is a great read and really nails the reasons behind improved middle and long distance running in the U.S. in specific and N. America in general.

That having been said, the depth at the collegiate level indicates the North American talent pipeline for middle and perhaps long distance running is as full as it has been in many years. It will be interesting to see if this ultimately translates into things like more international top 10 rankings, victories at major competitions and even Olympic medals.


My bet is that the East Africans might not seem so invincible in 10 years.


A Good Month

It was a good month for middle and long distance running that makes me as optimistic about the future of “my” sport as I have been for a long time. The growth of mass participation distance running by people committed to fitness has been the big story over the last 10 or 20 years. The re-emergence of a sizable number of elites in North America has the potential to be the frosting on this wonderful cake.


Moonshots & Medicine

Yesterday I was fortunate enough to land a featured op-ed in the New York Times about precision medicine in specific and the general topic of moonshots in medicine like the war on cancer.   For those interested in learning more about these topics here is link to a classic paper by Comroe and Dripps on medical innovation and goal directed progress via “big science” vs. blind luck and marginal gains leading to progress.   On a related note Bill Gates recently reviewed the 10 year results of his billion dollars of spending to improve health in the developing world. His conclusion was that not much had changed……


The graphic below is about the hype cycle. The question is always when and how long does it take to hit the plateau of productivity and just how high is it compared to the original expectations.




‘Moonshot’ Medicine Will Let Us Down –


Screen Shot 2015-01-29 at 8.23.08 AM



click for article



Demography, Destiny & Demographic Cliffs

It has been said that “demography is destiny” suggesting that at some level basic facts – like the distribution of the population in different age groups – are key determinants of what happens to a given culture, country or even the world. That having been said, it is well known that the “population is aging” and some have argued that the impact of aging on the world will ultimately be as big as the development of agriculture or the Industrial Revolution. I agree with this assessment and would add that aging is happening much faster and that we can see it coming in comparison the rise of agriculture and industrialization.


Countries age for two basic reasons: 1) fewer children being born per woman, and 2) people living longer.   These two factors also operate to determine the total population of a given country and the world as well. The chart below shows world population pyramids starting in 1950 with projects to 2100.




In 1950 the relative number of young people was far greater than older people. The so-called pyramid then gets progressively “squared” by 2010 and beyond.   This chart also projects total world population to be in the 9-10 billion range in 2010, it is currently about 7 billion.


China’s 1 Child Cliff

In the 1970s China took some pretty drastic population control measures including a strictly enforced 1 child policy. The rationale was to avoid famines. The policy has “worked” but now China’s population is rapidly aging and in fact the population of China is also projected to decline and population experts in China believe the 1 child policy needs to be reversed. The chart below shows the projections for China. The solid red line is the best estimate for what will happen this century with various high and low projections bracketing it. Subsequent charts for other countries follow the same format.





The impact of both an older population with fewer workers for every retiree and less total population is uncharted territory especially for a developing country like China. However, several more advanced countries like Japan and to a lesser extent Germany (and much of the rest of Western Europe) are already headed in this direction or at least headed to stagnating populations with a higher average age and fewer workers per old person.




In terms of both total population and the ratio of old people to workers, the US is relatively well off compared to China, Japan and most other developed countries. The reasons for this are more babies per woman and immigration.




Uncharted Territory

Population is a topic that leads to all sorts of discussion and debates:

  • What are the ecological costs of increased population and what is sustainable?
  • How aggressive should specific countries and the world in general be in promoting birth control and lower population growth?
  • If there are fewer workers per old person, how will old age pension systems and medical care be funded? This is a topic in the US, but it is also a topic essentially everywhere. The relative good news for the US also points out one advantage of liberal immigration policies – fewer young people to pay the bills.
  • Should the retirement age be raised?
  • What will the psychology of an older world be like? Young people take chances and roll the dice on all sorts of things while older people tend to be more risk averse and seek “certainty”. Will the aging population lead to less economic growth as a smaller faction of the world decides to “go for it”?


Who knows how all of this will play out, but if the phrase “demography is destiny” is a truism, it is likely to be especially true over the next 50 or so years. And, we can see at least some potential demographic cliffs coming.


Three Books & Our Messy-Crazy World

If you had any doubts about just how messy-crazy the world is, the terrorist attacks last week in Paris should have convinced you. I have been thinking about how to understand the Paris attacks in specific and the phenomenon of terrorism and political violence in general.   To do this I have started to re-read Eric Hoffer’s classic short book “The True Believer” first published in 1951.


In this book Hoffer outlines the causes of fanaticism and how it preys on alienated people with a sense of grievance who are looking for “something bigger than themselves”.   The book was a favorite of Dwight Eisenhower who had seen in World War II exactly what evil unchecked fanaticism can bring. He also saw echoes of it in the Cold War including the way the US and other democracies were responding. As recounted in the New York Times link above, in the late 1950s Ike wrote to a terminally ill WWII veteran seeking “clarity” on the complex national security issues of the Cold War.


“Eisenhower also recommended a short book — “The True Believer” by Eric Hoffer, a self-educated itinerant longshoreman who earned the nickname “the stevedore philosopher.” “Faith in a holy cause,” Hoffer wrote, “is to a considerable extent a substitute for the lost faith in ourselves.”


Though Eisenhower was criticized for lacking an intellectual framework or even an interest in ideas, he was drawn to Hoffer’s insights. He explained to Biggs (the terminally veteran) that Hoffer “points out that dictatorial systems make one contribution to their people which leads them to tend to support such systems — freedom from the necessity of informing themselves and making up their own minds concerning these tremendous complex and difficult questions.” The authoritarian follower, Eisenhower suggested, desired nothing more than insulation from the pressures of a free society.


Substitute “religious fanatic” a few places in the excerpt above and what Ike said in the late 50s is perhaps even truer today.


If you only read one book all year read “The True Believer”.


Book #2

If you want to understand the limits of our metric driven world and the efforts of economist, managers, and others to turn everything about humanity into some sort of measurable “science experiment” with a business angle, then read “Small is Beautiful” by E.F. Schumacher published in the early 1970s.   Schumacher points out that the human costs of economies of scale, bigger is better, growth is good, and all of the related activity needs to be considered skeptically along with ever more and more “return on investment” thinking.  As things have “grown” and become more globalized and hyper connected since the book was first published in the early 70s, Schumacher’s ideas and observations seem almost prophetic.


Does every human activity have a value that can be monetized, measured and managed? It sure seems that way……


Book #3, Man’s Search for Meaning

So in a world where it is easy to get either alienated and/or become essentially a cog in some sort of industrialized or commoditized activity, is there a way out?   The short answer is yes and one of the best resources to think about how to do this comes from the death camp survivor and psychiatrist Viktor Frankl. His book “Man’s Search for Meaning” was written in 1946 as he recovered from the Holocaust. He points out that in life there is no happiness without the pursuit of something beyond the self. One of his best observations is:


“Between stimulus and response, there is a space. In that space is our power to choose our response. In our response lies our growth and our freedom.”


To me this is a clear response to the industrialization and the increasing application of management theory to all human activities. We must choose to be more than organisms on some sort of stimulus response curve subject to manipulation


Connecting the Big 3

At some level the observation by Frankl above connects the major themes of these three great books. Themes of alienation and dehumanization run throughout the “True Believer” and “Small is Beautiful”. Some humans give up and essentially surrender. Unfortunately some of us are lured by mass movements and political or religious ideologies and surrender in a different way as we pursue “a purpose”.   I guess in the final analysis, the hard thing to do is choose your own responses to this crazy world.

Don’t surrender your choices too easily to outside forces that seek to manipulate them for their own gain.



Remarkable Old People: Share Your Story!

Over the Holidays I bumped into a colleague who told me about her 95 year old father (a retired pharmacist) who is still physically active and living independently. He walks two miles per day, and plays golf (he shot his age at 91, but is now “only” doing 9 holes). He is also active in his church and community. The other interesting thing is that “Dad” had a hard time retiring and for many years pinch hit in pharmacies in the upper Midwest that were short staffed. My colleague also mentioned in follow-up e-mails that her Dad lost his mother in childbirth, was a WW2 veteran who got off the farm and into the pharmacy via the GI Bill, and he also quit smoking back in the 1960s.


Did He “Know” Lester Breslow?

The graphic below is one I use in talks on healthy aging and “who makes it to 90”. It highlights the key principles on this topic that were discovered by the pioneering epidemiologist Lester Breslow. When I heard the story of my colleague’s father what Breslow discovered certainly seems to ring true for “Dad”.




Circumstances & How You Respond

The other thing that hit me about “Dad” in specific and that also seems to apply to many healthy agers is how resolute and resilient they have been over the years. Somehow they all seem to understand — or maybe have learned — that you can’t always control the circumstances you find yourself in but you can control how you respond. At some level this may be a learnable life skill and the Holocaust survivor and famed psychiatrist Viktor Frankl felt that resilience can be learned. He noted:


“Forces beyond your control can take away everything you possess except one thing, your freedom to choose how you will respond to the situation.”


Please Share Your Story

I personally find stories like the one above to be incredibly interesting and inspiring. If you have one, please share it in the comments section and in a future post I will highlight the key messages and insights.


Thanks and remember the words of John Wooden:

“Do not permit what you cannot do interfere with what you can do.”




New Year’s 2015: Drinking Charts to Ponder

Who can think about New Year’s without thinking about drinking. The chart below is about 15 years old but still considered accurate and shows the relationship between drinking and the risk of cardiovascular disease. It shows that moderate alcohol consumption (essentially 1-2 standard drinks per day) is generally protective.






While moderate drinking is generally good for you, it is important to remember that binge drinking (4 drinks for women 5 for men) is bad news, and it is common.




The highlights of the bad news according to the CDC include:


  1. Motor vehicle crashes. Every day, 32 people in the United States die in motor vehicle crashes that involve an alcohol-impaired driver.


  1. Intimate partner violence. About 2 of 3 incidents of intimate partner violence are associated with alcohol.


  1. Risky sexual behaviors. Excessive drinking increases risky sexual behaviors, including unprotected sex and sex with multiple partners, which can result in HIV infection, other sexually transmitted diseases, and unplanned pregnancy.


  1. Fetal alcohol spectrum disorders. Any alcohol use by a pregnant woman can cause harm to a developing fetus, resulting in physical, behavioral, and learning problems later in life.


  1. Chronic conditions. Over time, excessive drinking can lead to alcohol dependence, liver disease, high blood pressure, heart attack, stroke, and certain kinds of cancer.



The data above and resources in the links speak for themselves. Enjoy New Year’s and every other social occasion that includes alcohol but remember that alcohol is perhaps the most dangerous drug and needs to be used judiciously.