Human Limits

A number of recent posts have focused on what might be called the “geopolitics” of healthcare and the Federal budget in the United States and offered analysis and ideas about how things like sin taxes and insurance plans might incent healthier behavior.   Today I want to get back to human performance and elite athletes, topics that were covered in detail last summer during the Olympics.   The twist here is that I want to talk about elite 80 year old endurance athletes.

In an amazing scientific paper, scientists from Ball State University in Indiana, along with collaborators in Sweden, found 9 elite cross-country skiers (including an Olympic Champion) who had remained highly physically active and trained throughout life.   On average these individuals had VO₂  max values of 38 ml/kg/min.  This is a value similar to that seen in sedentary men in their teens and twenties.   It is also a value about 80% higher than the values seen in sedentary 80 year olds.   VO₂ max is a marker of the ability of the heart and lungs to deliver oxygen to exercising muscles and also the ability of the muscles to use oxygen.   A simple analogy is that VO₂ max somewhat similar to a measure of horse power for a car.   With more horse power you can do more!

Below is a figure from the paper.   The key point is that a VO₂ max value of about 15 is required to be functionally independent and that the untrained octogenarians were likely drifting downward toward that value, while the athletes had plenty of reserve and extra capacity.    Another key point that my colleague Jill Barnes and I made in an editorial on this paper is that while the high values in the athlete’s likely had a component of “natural ability” or “genetics”, it should be possible for highly active regular guys in their late 70s and 80s to have VO₂ max in the high 20s or lower 30s, or about twice the value needed to remain independent.

This paper raises a lot of questions about things like what kept these men motivated to stay so active throughout life.  It will also be interesting to see what the data in older women looks like as more women participate in endurance sports throughout life.    While there is no fountain of youth, the data in these older elite athletes is just another example of what lifelong exercise can do.

People exercise for all sorts of reasons including being in better shape to meet the challenges of daily life, weight control, general health, being able to keep up with their kids and grandkids,  and participation in competitive activities.   But what is the long term payoff in terms of extra years lived or longevity?   There is some fascinating new information on the question that comes from a pooled evaluation of a number of large studies conducted over many years by the National Cancer Institute on lifestyle and health in about 650,000 people.

There was enough data in these studies on physical activity and things like BMI to do rigorous statistical analysis on a couple of questions.   First the authors had to divide the subjects into groups based on how much physical activity they got per week.   The used something called “Met Hours”.   A met is a marker of how much oxygen you use per minute at rest and reflects your energy consumption.    Brisk walking takes about 3 mets.  During peak exercise healthy lean people in their twenties who are untrained max out at about 10-12 mets when they are tested on a treadmill.  Without training these peak values fall perhaps 10% per decade starting in our 30s.   Elite athletes can achieve max values of 15-20 mets.

The paper categorized people into six activity groups equal to brisk walking for 0, 1–74, 75–149, 150–299, 300–449, and 450+ minutes per week.   In terms of “met hours per week”, these walking categories equal 0, 0.1–3.74, 3.75–7.4, 7.5–14.9, 15.0–22.4, and more than 22.5.   Most public health guidelines suggest that 150-299 minutes of moderately vigorous exercise (7.5 to 14.9 met hours) are a key for good health and significantly reduce the risk of things like diabetes and heart disease.   The figure below shows the longevity findings.

The authors of the study concluded that:

…..adding even low amounts of leisure time physical activity to one’s daily routine—such as 75 min of walking per week—may increase longevity. This finding may help convince currently inactive persons that a modest physical activity program is “worth it” for health benefits, even if it may not result in weight control. Physical activity above the minimal level—at recommended levels, or even higher—appears to increase longevity even further, with the increase in longevity starting to plateau at approximately 300 min of brisk walking per week. Finally, a lack of leisure time physical activity when combined with obesity is associated with markedly diminished life expectancy. Together, these findings reinforce prevailing public health messages and support them for a range of ages and backgrounds: both a physically active lifestyle and a normal body weight are important for increasing longevity.”

There is not much to add to this except that people who are active also have more disability free years at the end of life.   Thus the active live both longer and are more independent as they age with fewer chronic medical problems.

A few weeks ago I pointed out that age associated cognitive impairment and Alzheimer’s disease shared many risk factors with cardiovascular disease.    The brain shrinks as it ages and it shrinks faster in people with cognitive impairment and Alzheimer’s disease.   There are also other subtle structural changes associated with aging and cognitive decline.   A recent paper in the journal Neurology reported on how physical activity affects brain volume in almost 700 people in their 70s who were studied in England.

“A higher level of physical activity was associated with higher fractional anisotropy (a marker of brain structural integrity), larger gray and normal appearing white matter volumes, less atrophy, and lower white matter lesion load.  The physical activity associations with atrophy, gray matter, and white matter lesion remained significant after adjustment for covariates, including age, social class, and health status…..”

Conclusions: In this large, narrow-age sample of adults in their 70s, physical activity was associated with less atrophy and white matter lesion.  Its role as a potential neuroprotective factor is supported; however, the direction of causation is unclear from this observational study. “

The paper goes on to discuss factors that might be responsible for the positive effects of physical activity on brain size and function.  There is evidence that exercise stimulates the growth of new brain cells and improves connections between brain cells, so no major surprises here.

The paper also mentions that exercise may also improve blood flow to the brain.  The figure below is from a study done in my lab by Dr. Jill Barnes.   It shows using a measurement called CVCi, that the ability of the brain blood vessels to relax and vasodilate (usually a good thing) in response to CO₂ is lower in healthy 60 somethings vs 20 somethings.  In both age groups a drug called indomethacin reduced the vasodilation in response to CO₂.  Blood flow at rest was also lower in the older subjects, or as Dr. Barnes put it:

“Young adults demonstrated greater MCAv (index of blood flow) 55 ± 6 vs. 39 ± 5 cm/s and MCAv reactivity 1.67 ± 0.20 vs. 1.09 ± 0.19 cm·s to hypercapnia (CO₂) compared with older adults.”

The next figure I want to show you is from a study on aging and brain blood flow in trained and untrained male subjects.

The authors commented that:

This ∼17% difference between trained and sedentary men amounted to an approximate 10 year reduction in MCAv (blood flow) ‘age’ and was robust to between-group differences in BMI and blood pressure. Regular aerobic-endurance exercise is associated with higher MCAv in men aged 18–79 years.

Summary:  Exercise and physical activity do good things for your brain as you age.  They help you grow new cells and they keep blood flow to the brain high.   One idea is that blood flow is higher because the brain remains bigger in those who are active as they age.   The other interesting thing to note is the “10 year” anti-aging effects of exercise on blood flow.    That number, or perhaps an even higher one, seems to be pretty consistent for the anti-aging effects of exercise on many elements of our physiology.

Today’s post is about how to get the most out of your indoor training.   My motivation is that up here in Minnesota more people will be doing more of their exercising indoors in the winter months.   I am not sure when the shift begins but I hear from studio cycling instructors that class size starts to pick up in October and remains high until March or April.

In the pre-gym, fitness center, and indoor exercise equipment era a few brave souls went outside to run “no-matter what”.   The advent of better protective clothing in the 1980s helped, and I can remember putting titanium screws on the bottoms of old running shoes to improve footing and grip on the ice.  Equipment and clothing for outdoor exercise have gotten better but thankfully I have gotten less macho and am now happy to be indoors most days during the “deep winter” or even the “deep fall”.

In previous posts I talked about the value of interval training for all and also provided some ideas about how to get the most out of your training as you age.  In this post I want to give you some ideas about good ways to maintain your fitness indoors based on what has been described as the “Hickson Protocol”.   It comes from a 1977 paper called “Linear increase in aerobic power induced by a strenuous program of endurance exercise.” 

What is the Hickson Protocol?
The protocol consists of exercise 6 days per week for 10 weeks.   On days 1,3, and 5 the workout is six 5-minutes maximal cycling intervals separated by 2-minutes of easy cycling. On the alternate 2,4, and 6 it is 40 minutes of hard running.  The figure below shows that when untrained subjects first used the protocol they achieved vast increases in maximal oxygen consumption (VO₂ max) over the course of the 10 weeks of training.

Who wants to train this hard every day forever?
The short answer is not many people and when the original 8 subjects were offered the chance to continue beyond the original 10 weeks they all said no!   However, this study does show just what is possible with hard training.

How can I use this data to plan my winter training?
Most people reading this probably already exercise and some of you are competitive athletes and already do at least some high intensity training.   Hickson can help us here.  He did a number of similar training studies and then asked people to reduce their training frequency, duration, or intensity in various ways to see just how much (or how little) exercise was required to maintain VO₂ max at a high level.  He ultimately showed that brief periods of intense training a few times per week were remarkably effective in maintaining VO₂ max at a high level.

“We conclude that it is possible to maintain almost all of the performance increases with up to a two-thirds reduction of training duration. Nevertheless, the data provide initial evidence that all aspects of the endurance-trained state may not be regulated uniformly in reduced training, particularly since VO₂ max and short-term endurance were maintained, but long-term endurance decreased in the 13-min group.”

Summing up.
Clearly there is more to training and competing successfully than doing intense exercise just a few times per week for a few minutes.  However, the winter is a time when many people do a little less and the Hickson studies show that if you do a bit of high intensity exercise every week it will be easier to gear up when the weather gets better and the days get longer.   The Hickson data is also helpful for planning your training when you are traveling or have limited training time.   You can clearly accomplish a lot with 30-45 minutes per day of training, and maintain things with even less.

I got an e-mail over the weekend from a reader who was a world class runner in his youth and getting ready for an upcoming half marathon.

“Michael: I seem to have hit that mid-60s point where things deflect a little on the difficulty/slower-speed curve. Trying to stay positive…..”

That having been said, I was thinking about doing a post on the lack of discussion in the election about the real problems confronting health care in the United States.  Most of the yapping seems to be about how various insurance programs might be organized and misses the fundamental point that if things don’t change the combination of inactivity, obesity and aging is generating a tidal wave of chronic diseases that will bankrupt anything that is being discussed.    However, the aging and speed curve issue raised by the reader above is more fun and there are some pretty simple ways to address it.

First, what is meant by the “slower-speed curve”?  If you plot records vs. age for almost any distance running event you get a graph like the one below.   I did this one 20 years ago for a scientific review on aging and endurance performance and it plots age vs the US record for 10K road race time.   The times have changed since then but the trends are pretty similar.  (If any enterprising student who might be reading this wants to update the curves let me know and we can set up a guest post on the topic.)

You can see that times are best for competitors from their early 20s until the middle or later 30s.   After the late 30s, things decline at a rate of about 6% per decade and the rate of decline increases somewhere in the 60s for men.   The data for women is similar but a little harder to interpret because we have not seen the full effects of Title IX and increased participation by women on the age group records.   While this data is for record performances by many different runners, many individuals report similar personal experiences and note, as the reader did, that something happens in their 60s.

Second, what happens in your 60s?  There are several possibilities.  From a biological perspective, things like peak heart rate decline as we age, but the rate of decline does not accelerate in your 60s.  That having been said, something called sarcopenia (age related muscle loss) probably starts to accelerate in the 60s.   If you look at people who tend to maintain their performance over time, there is evidence in men that those who decline the least keep their lean muscle mass and training intensity up.   In women it appears to have more to do with training volume (milage) and hormone replacement therapy.   However, I want to point out again that less is known about female master athletes, and there is some evidence that in terms of training intensity, what applies to men applies to women as well.   Here is a link to an article on Kathy Martin who is rewriting the record books for older women.  Note that she does a lot of high intensity training and my understanding is that she has added milage only recently with her move up to the marathon.

The other issue here is that injuries and other health issues catch up with people as they get older and perhaps it is just harder for most folks to train as consistently and consistently hard for these reasons.

Third, can you beat the speed curve?  My personal opinion based on a combination of observations, discussions with others, and a tiny bit of research driven evidence is that training quality is the key.   I would advocate that in your 50s and 60s you might cut your milage back and do most of what we used to call “over-distance” training on the bike or in the pool.  This will let you focus your running on higher quality efforts and provide a lot of bang for the buck with minimal orthopedic risk.   An interesting anecdote is that in the early 1990s the legendary Fred Wilt, a world record holder in the 1940s, told me that when he was in his 50s he came close to breaking 10 minutes for 2-mile.   His training consisted of jogging a few minutes mile to a track near his home and doing two miles of alternating fast and slow 200m runs very hard and then jogging home.  He did this about 4-5 days per week.

Consistent with what Fred Wilt was doing in his 50s, he documented in several books the training used by athletes who ran some pretty incredible times prior to the “modern” ideas about training emerged after World War II.  Much of it seemed to consist of things like 4-5 miles of hard running followed by some all out sprints 4-5 days per week.   I personally try to do something like this 2-3 times per week, and sometimes do the sprints on the bike trainer to keep the risk of injury to a minimum.   The other thing I like to do is 20-30 minutes of hard steady riding on a trainer followed by 20 minutes of 1-minute on/off of fast-slow running.   The advantage of using a treadmill and bike trainer to do this type of training is that it may be a bit easier to push yourself.  I am 54 and following this plan as I prepare for a 5 mile Turkey Trot on Thanksgiving.

Fourth, why will this work?  In an earlier post on distance running and the Olympics this summer I covered the concept of VO₂ max and its role in setting the upper limit for endurance performance.  The type of intense training discussed above and very hard efforts of 3-5 minutes are the keys to keeping your VO₂ max as high as possible while you age.   I also think that biking vs over distance running is a good way to keep your muscle mass up.   I am always impressed at how the best master athlete cyclists and swimmers seem to have maintained their muscle mass in comparison to distance runners who sometimes look a little wasted.

Summary:  The ideas above represent my best guesses about how to maintain a high level of performance especially in your later 50s and 60s.  They are designed to limit the risk of injury.  There is scientific evidence for most of these ideas and there are real world examples showing that these ideas work.   We all eventually lose the battle with aging; the key is to lose it slowly by walking, running, biking, or swimming fast.

Last week I had the opportunity to attend the “Integrative Biology of Exercise” conference sponsored by the American Physiological Society.   During an excellent talk on how exercise training can modify the changes in heart function with age, Dr. Ben Levine showed classic data from a study done in the middle 1960s known as the Dallas Bed Rest Study.

In this study 5 healthy young men did nothing but bed rest for three weeks while detailed measurements of their cardiovascular function and exercise capacity were measured.    Not surprisingly, cardiac function declined and exercise capacity fell dramatically with bed rest.   The figure below shows what happened to VO₂ max which is considered the gold standard measurement of exercise capacity after bed rest.

What is even more interesting about this figure is that when the same subjects were studied 30 years after the original bed rest study, their VO₂ max fell more with just three weeks of bed rest than with 30 years of aging.   Below is a video link of Dr. Levine talking about his work on related topics.

 If video does not load, click here.

Another interesting video on the topic of inactivity comes from Dr. Bente Pedersen of the University of Copenhagen.    Her team has conducted an incredible study showing that just two weeks of minimal physical activity can put previously health young men on the path to what might be described as pre-diabetes.    In the video below she discusses these findings and also concepts related to the fit vs. fat topic covered a few posts ago.

If video does not load, click here.

These are terrific talks by scientific leaders who are my friends and colleagues.  One of the great things about the electronic environment is that presentations by such outstanding investigators are available to us all.

There has been a lot of talk recently about the long term health risks associated with U.S. football.  There are two main concerns, the first relates to the long term effects of concussions and cognitive impairment later in life.  The second relates to the long term health risks associated with being “very big”.

It turns out that the neurological consequences of football are more typically seen in so-called speed positions that are associated with high velocity open field “big hits” in comparison to collision positions like the line.   The non-neurological long term health risks of professional football go something like this:

“National Football League players from the 1959 through 1988 seasons had decreased overall mortality but those with a playing-time BMI ≥ 30 had 2 times the risk of CVD mortality compared to other players and African-American players and defensive linemen had higher CVD mortality compared to other players even after adjusting for playing-time BMI.”

Some of these concerns were highlighted in a piece by the columnist George Will who summarized it this way:

“Decades ago, this column lightheartedly called football a mistake because it combines two of the worst features of American life — violence, punctuated by committee meetings, which football calls huddles. Now, however, accumulating evidence about new understandings of the human body — the brain, especially, but not exclusively — compel the conclusion that football is a mistake because the body is not built to absorb, and cannot be adequately modified by training or protected by equipment to absorb, the game’s kinetic energies.”

WHAT TO DO ABOUT IT?

The first thing to remember is that the modern game of football emerged after deaths in college football in the early 1900s led President Theodore Roosevelt to demand that the game be reformed or banned.  So, the safety of football is not a new issue and in that spirit I make the following suggestions:

1. Limit substitutions.   If players had to play both ways my bet is that the premium on very large players (300 pounders) would be replaced by a premium on big but not huge players who had the athletic skills to do more than one thing and also the stamina to play for longer.   When teams go to no huddle offenses frequently their defenses complain about the lack of rest caused by an offense that gets off the field too fast.  So, there would be a new emphasis on conditioning.
2. Shorten the time between plays.  If there were a 20 second clock between plays the game would be more continuous and that would make conditioning even more important and limit the utility of really big players.  It might also limit the likelihood of pre-planned, high speed big hits.
3. Get rid of some of the protective equipment.    It is unclear if the protective equipment is in fact that protective.  Perhaps it gives the players a false sense of security and encourages them engage in high risk, high impact hits.

Some of the ideas above would make U.S. football more like rugby so I bounced them off four outstanding physiologists from rugby loving countries:  Danny Green and Bob Callister from Australia, Tim Noakes from South Africa, and Peter Raven originally from the UK.    All of my colleagues agreed the ideas above had merit.    Dr. Green sent me a fascinating paper about body size in rugby and how it has changed over the last 100 year, and it is unusual for a top class rugby player to be much bigger than 110kg (about 245 lbs).

In closing, I doubt the ideas above will ever be adopted wholesale, but various forms of football have existed for centuries and perhaps the game will evolve in the ways I have outlined above.  If so, I bet we will end up with a safer game to play and watch that is equally exiting.  Watch a clip of the 7 on 7 version of rugby that will be coming to the Olympics in 2016 and see wide open game.   Add the forward pass and imagine what would be possible.

I got an e-mail a couple of days ago from a friend and reader who is world-class engineer/leader for a large company who just returned to the US after several years on an overseas assignment.   Here is an extract from the message:

“I read the blogs for the past month, very interesting.  There was a lot of coverage of obesity…….something I know firsthand, all too well, unfortunately.  You’d think I’d listen to such good advice and make some changes.  But, as you say, it is a complex issue.  I hope that just one poor risk factor out of six, will not be too bad.”

This got me thinking about the whole obesity issue and perhaps it is time to stress some good news.  That having been said, there is pretty convincing evidence that remaining fit and active can trump a lot of the negative health risks associated with obesity.   The graph below shows the relative risk (RR) for all-cause mortality (top panel) and cardiovascular disease (CVD) mortality (bottom panel) in lean, normal and obese subjects.  The dark bars are for unfit people and open bars for fit people.  The study comes from the Cooper Center database and included almost 22,000 men.   The numbers of above the bars are numbers of deaths in each group over a multi-year period of observation.

The dark bars show that obesity puts people at increased risk for both all-cause mortality and cardiovascular disease.   This increased risk is clearly amplified by being unfit.   By contrast, all-cause mortality was lower in the fit people and the amplifying effects of excess body weight were much less.  There are all sorts of reasons why being fit and active can trump other risk factors like obesity; less diabetes, blood vessels that can stay relaxed, and better blood pressure control to name a few.   The other issue here is that people need to avoid getting hung up on losing a set amount of weight to reach an “ideal”.    Losing just 5 or 10 pounds can really make a difference in a number of risk factors and is especially effective if it is accompanied by more physical activity.

So here is an encouraging thought from a recent study for people who worry about their weight:

“Higher fitness should be considered a characteristic of metabolically healthy but obese phenotype. (ii) Once fitness is accounted for, the metabolically healthy but obese phenotype is a benign condition, with a better prognosis for mortality and morbidity than metabolically abnormal obese individuals.”

Or as Dr. Chip Lavie, a noted cardiologist and fitness expert from New Orleans, said recently in the New York Times:

“Maintaining fitness is good and maintaining low weight is good, but if you had to go off one, it looks like it’s more important to maintain your fitness than your leanness……”

So don’t get discouraged, do stay active, and don’t get too hung up on your weight if you are staying active.