December 2018

With 2019 almost upon us, it’s a good time to think about topics for my blog next year.  Immediately, the description of what I’ve gone back to school to study blips up: aging and performance.  Informed by what I learned last semester, let’s look at these terms. 

Aging.  What a huge topic!  There is muscular, bone, joint, ligament, neural, and mental aging, all drawing on changes in our cells that make up those structures.   For runners, and all athletes, these factors simultaneously affect us in varying ways and at various stages of life.

First, it’s important to distinguish between chronological and biologically aging.  Many elements of aging begin to show themselves around age 40.  In Bending the Aging Curve (2011), Joseph Signorile suggests there is a huge difference in neuromuscular function (a combination of many of the above-listed things) among life-long trained athletes, who have the highest NMF, those who started training at 40, and those who have never trained.  This is good to remember and hardly a surprise.  But whatever our starting point, we do experience changes as we age.  Let’s consider three.

First, Type II (fast-twitch) fibers tend to increasingly turn into Type I (slow-twitch) fibers after age 40.  Which means top end-speed is affected more than our 10K or marathon pace.  For the distance runner that means we see a declining kick and slower timed repeats.  If we used to find a 6:00 minute/mile pace a reasonable benchmark, that becomes increasing hard or impossible to achieve.  The good news is that the more resilient Type I fibers hang on longer and allow us to continue with solid long-distance racing into our 50s and well beyond.

Second, maximal cardiac output (CO), which is the product of stroke volume and heart rate, decreases with age.  CO is the amount of blood we circulate in one minute. For most people, at rest it approximates total blood volume, meaning our entire blood supply circulates in about one minute. During strenuous exercise that circulation rate roughly triples with our muscles screaming for an increased amount of blood replenished with oxygen and nutrients.  Training helps our bodies build this capacity in both production and efficiency of use.   But even highly trained athletes see decreases in their top-end CO.  The standard formula for maximal heart rate is 220 minus age.  While this varies by individual, the formula suggests a maximal rate of 200 bpm for a 20 year old and 150 bpm for a 70 year old.  Based just on HR, this suggests a 25% decrease in CO.  And stroke volume, a measure of blood pumped with each beat, is also taking a hit, as even healthy arteries stiffen with age.

Third, ligaments and tendons slacken.  While we may feel more tight and sore after running now than in our youth, in fact much of our connective tissue is looser and less dense.  Tendons and ligaments serve as elastic springs for muscles and joints.  This elasticity gives us lift and bounce when we run.  Take the Achilles tendon.  We rely on the Achilles for push-off, which enables gait height and stride length.  As the Achilles becomes less elastic, our ankle, which functions as a biological hinge, doesn’t have the same pop. We’re working hard, but not moving as far with each step. 

Perhaps that is enough about the physical impacts of aging for this round!

Performance.  Webster’s defines performance as “an action or process of carrying out or accomplishing an action, task, or function.”  Well enough.  Certainly this means different things to different people.  Unfortunately for some, navigating the activities of daily living (ADLs) is a form of performance.  

For this blog, I am looking at this from the perspective of exercise physiology.  Permit me to pose a question: Is someone running a 60-minute 10K “performing” in the eyes of a 38-minute 10Ker?  Maybe, maybe not.  And that 38-minute runner who clocks a 40:00 may mutter, “I was off today, I didn’t show up.”  The point is performance is relative to each of us.  And it changes as we age.  Running is a sport that requires us to live in the present while inviting us to remember (and celebrate!) the past.  I regularly run with a friend who ran a 4:10 mile in college.  Today, at 63, he’s pushing (really pushing!) to hit 6:30 mile repeats.  He knows he’s a few pounds overweight and due to job and family responsibilities not consistent with his training.  But I know he considers himself a performer when he toes the line at a local race.   Another case is a 27 year-old extended family member training to run her first marathon.  Based on her long runs, I think she’ll do well to run 4:30.  If the question is put to her, yes, she will be performing!

Thus, I suggest performance is something of a state of mind.  At the collegiate level, there are standards to meet if one is to compete in a conference, regional, or national event.  And there are qualifying times for the Boston Marathon.  However, for most of us, those times are irrelevant.  We look at our planned race schedule, set target times, and broadly determine what kind of training quantity and quality will be needed to meet those goals.  We are indeed expecting to perform!

As the year unfolds, I am sure to come across many avenues to explore on this topic of aging and performance.  There are no simple answers.  Ultimately, we must be forthright and honest with ourselves about what running means to us, and then gauge our commitment and the trade-offs we are willing to accept to attain a level of performance we are satisfied with.