Tuesday, July 19, 2016

Of Mice and Men: How does the biology of running evolve?

Mobility as an Emergent Property of Biological Organization: Insights from Experimental Evolution

Evolutionary Anthropology just published a fantastic article (linked above, full text) summarizing 20 years of research with mice selectively bred to run.  That is, mice that voluntarily run more distance per day have been bred together for generations, producing mice that are biologically better at running, and willingly run longer each day, than other mice.  If you're wondering how this is informative or productive: selective breeding is used by scientists all the time to understand how real evolution occurs and how biology changes as particular traits become more common.  Selective breeding is a lab-controlled simulation of real selection-- natural selection-- that occurs in nature.  In this case, these studies have produced some fascinating insights into how evolution produces a biologically-equipped mammalian runner.  As we are also mammals, these mice studies raise all kinds of testable questions regarding the evolution of human running. 

For anyone not wishing to chew on the review article above (though it is very digestible, I think, perhaps even for non-science folks), here I'll summarize the significant differences that have been observed in running-bred vs. non-running mice. (Note that these closely, but do not entirely, follow the bullet points in the article.)

Mice bred to voluntary run more have led to generations of mice that, well, run more.  (Mostly because they run faster, actually.)


What mice tell us about the evolution of running

1. Running is compelled by biology.  You and I might consciously decide to head out the door for a run because we know it will make us feel good.  Or lose weight. Or whatever.  Other cursorial (running) animals aren't motivated by this foresight but rather by unconscious drives.  These drives (which we have too! Check out "Wired to Run"-- your brain makes pot-like chemicals when you run) directly motivate animals to move.  They have likely evolved because running serves some survival purpose.  In mice, I have no idea what that could be, but in dogs and wolves, it's food acquisition: an animal that is motivated to run covers more territory and finds more food.  Hence, those genes are passed on more successfully than couch-potato dogs, and so evolution goes.  We know that the drive to run in the running-bred mice is genetic and biological, and not learned, because it is present early in a running-bred mouse's little life, before they have had a chance to get used to a running wheel.  In short: the urge to run can be genetic and biological, and therefore it can evolve through natural selection.

What are some of the mechanisms of this biology that motivates animals to run?  Well, in humans and dogs, it's the aforementioned endocannabinoids (see link above).  In mice it seems to be a change in how the brain chemical dopamine functions.  Here's an example of "convergent evolution"-- similar solutions arising independently in different animal species to solve the same problem. 

2. Selection for increased motivation to run, and running ability, comes with lots of biological changes.  Some are mentioned above-- changes in reward pathways in the brain which encourage animals to run.  In wolves and dogs--who clearly have an excellent evolved running capability- certain biological traits have an obvious positive effect on running performance: muscle composition, leg length, etc.  But the selective breeding experiments with mice demonstrate how some of these characteristics can evolve, or change, from a baseline population of non-running-adapted animals.  Running mice, over generations, developed a higher VO2-max (oxygen carrying capacity) than non running mice; decreased body size, leading to more efficient running; decreased calf muscle size, which is good for endurance running because it reduces the weight lifted with each stride; increased midbrain size (possibly to increase the reward pathways discussed earlier, or to aid in coordination); increased surface area in the leg joints, good for shock absorption; and intriguingly, differently-shaped semicircular canals, which are structures in the head important for balance and thought to be essential for frequent and effective endurance running.  I say "intriguing" because this last observation is also seen in the fossil record early in our genus, as are many of the other evolved traits of the running-bred mice.  It would be rash to directly apply observations of artificial selection in mice to human evolution, but these results (to me) point to things we should look for in human evolutionary history when testing hypotheses about whether, when and how humans evolved to run.  And the fact that we see similar traits in humans is tantalizing. The takeaway: selection for increased running performance does indeed lead to genetic, biological changes that improve running ability.

3. Evolved running ability comes at a cost, and is constrained by evolutionary "trade offs".
I often joke that the better I get at running, the worse I get at everything else.  There is truth in this at an evolutionary level: traits that enhance one thing will likely have a negative (or sometimes positive) impact on other things.  A great example is Herman Ponzter's observation that, in cursorial mammals, hind limb length has evolved for running efficiency, but only to a point: super long limbs would cost a lot to grow during development and would decrease sprinting speed far too much.  When evolutionary costs outweigh benefits, a trait will cease to become more pronounced over time- it will have reached an equilibrium of sorts, a compromise.  Similar constraints are observed in the "evolution" of our running mice.  Their reduced calf musculature makes them slower sprinters, and in a natural setting with predators, natural selection would likely work to reduce this calf-shrinking trend, despite any advantages it might convey for endurance running, which for mice would be almost nothing-- they are not endurance runners, let's remember.  (Interestingly, as an aside, this trait is caused by a single allele for a single gene. Also interesting is that the size and location of calf musculature in human runners has a significant effect on running economy.) This trade-off between endurance and speed surely limits the endurance-running adaptations that any cursorial animal develops.  Perhaps humans too, though sprinting can't have been especially helpful to us in my opinion, because even Usain Bolt would have trouble outsprinting an African carnivore.  

Anther tradeoff observed in mice: increased corticosterone levels in the running-adapted mice is helpful in that it increases fuel availability for muscles and encourages running behavior, but decreases immune function, inhibits growth, and may lead to depression (sad little mice). The first two effects, if at play in the evolution of any running species in a real setting, would incur significant fitness penalties and would therefore be highly constrained. 

Finally, like any other complex trait, endurance running motivation and ability is influenced by many genes, some of which have many different jobs and effects.  (This is called "pleiotropy".) This helps explain the trade-offs mentioned above, but it also explains some of the stranger results found in the mice study, like the observation that running mice "build smaller nests in their home cages, display greater predatory aggression towards crickets, and have a slightly altered finger-digit ratio".  The latter is also found in humans to predict athletic and running ability.  Like the other weird observations, finger ratios have no direct effect on running performance, in humans or mice.  Rather, they are influenced by similar genes, like the ones encoding the hormone testosterone.  Genetic changes that evolve to enhance running ability also have other weird side effects that will simply come along for the ride, and won't be selected against unless they are super deleterious.

Unfortunately (or maybe fortunately for me) there are still very few researchers asking evolutionary questions about human running, so it will be years before some of these insights are applied to humans. 

Wednesday, July 13, 2016

1.5 million year old footprints....

...in Ileret Kenya demonstrate a modern human foot in Homo erectus.

http://www.nature.com/articles/srep28766#abstract

Figure 1

I met the lead researcher in San Francisco in 2015 and I am floored by the methods he uses to infer so much from these amazing prints.  A modern foot with a longitudinal arch is also a foot capable of efficient running...

Tuesday, July 12, 2016

Racin': Summer Part 1

I thought that maybe I'd sworn off writing race reports, but I suppose that investing all this time into running means it's also worth processing that running, maybe even with written words.  Plus, for the handful of you who actually read this stuff (thanks!!), I guess this is no worse than Keeping Up with The Kardashians (is that still a show?)...at least I'll condense this into one post to minimize the bloat.

Preparation: Winter and Spring
Since I adopted an obsessive focus on mountain racing in 2014, my training for these races begins in earnest in January.  This winter I managed to stay on the trails a bunch, even in the snow (though we didn't have much), and that was a rad development.  (I even got in a few trail runs with the force of nature that is Josh Ferenc.)  Shedding the sallow shell of a lifelong road runner (ooh, nice alliteration Drew!) will, at some point, mean learning how to run trails in the snow.  This winter didn't require snowshoes, not really, but we'll see how I fare when a real winter hits.   The weekly long run with my boys Matteo and Stoneman was in the woods when possible but sometimes stuck to the roads.  Training also included a short "fast" workout of some kind, though these were often sacrificed for recovery (something I'd later regret).  My key workout, though, in winter and spring is a treadmill hillclimb.  I picked this up from Eric Blake who is one of the country's (if not the world's) best uphill runners.  Basically, crank up the incline and run near anaerobic threshold pace for 30-60 minutes--which not coincidentally is the effort that you'll run for most of the Mt. Washington Road Race, which averages 12% grade.  In 2014 and 2015 I ran 5-7 mile tempos at 10-12%, which became race effort in the last few miles every time, and I did this from January right through the summer mountain racing season.  These were brutal and I decided that they were doing more harm than good.  So, this winter I decided I'd scale them back a bit, avoiding full race effort, and instead focus on working inclines of 14-15%, starting with workouts chunked into 2 mile segments and working up to 5 mile tempos.  This approach was hit and miss; I had some balls-out fantastic workouts and some blowup deathmarches on the treadmill.  I wasn't sure what to make of my fitness.

Come May most of my running other than the treadmill workout and the too-infrequent fast workouts were on trails, my mountain bike rides were always 2 hours and rather serious, I was lifting heavier weights than I have since I was 21, and I had a decent outing in my cornerstone 4x Mt. Toby workout.  But still, the treadmill workouts had me wondering what I could do come the uphill races of June and July, and I still had trouble recovering from one workout to the next.  To illustrate what I now view as "normal" fatigue: I can't walk in the morning.  My achilles tendons and calves take about 30 minutes to function, as in, move at all.  To let the dog out requires stepping down 2 stairs, which I do while holding onto the wall.  In short: I was training at my limit, per usual...there was nothing more I could do to get ready for the season.

May: Soapstone Mountain Trail Race
won some steel pints.  photo by Scott Livingston.
I didn't race until May.  This should have been the first real test of my fitness and I headed to this ~13.5 mile trail race with intentions of setting a course record, a good mark set by regional mountain/trail/road star Jim Johnson.  This was not to be, largely because my homeboy Matteo and I, leading the race after the initial blazing dirt road mile, followed the wrong arrows into the woods.  Yes, the entrance to the trails was marked in two directions.  This pissed me off incredibly.  Five of us spent 7 minutes off course, and upon returning, Matteo and I spent probably 2 miles passing the entire field (including walking up the steepest climb behind some folks with headphones on) and generally deciding whether or not to re-engage race effort.  Eventually I worked back up to 95% effort and passed the field, winning in ~1:50, not knowing if I could have broken the record of 1:36.  Dammit.  But, a good day with Matteo (who finished 2nd) and Stoney, and really one of only a few times I've "raced" a pure trail course, which is rather silly.  I've got to do more trail races that aren't just up mountains.

results

June: Ascutney Mountain Race
from Wifey's hike, while I raced. What a nice mountain.
This staple of the USATF-NE Mountain Series falls 6 days before Mt. Washington.  This is probably not a coincidence as it is almost exactly half of the bigger mountain-- 12% for 3.7 miles.  This year I ran slower than the last 2 years, finished 2nd to a guy who I think just moved back to New England and so I wasn't expecting him, and left feeling crushed by the prospect of running up Mt. Washington against world-class runners with what was apparently subpar fitness.  No matter...it was a fun weekend of camping with Stoneman (he's a regular feature here, eh?) and Wifey, and the best part was hiking around on the summit trails, in the fog the evening before.  Alpine woods (especially on mountains in New England) are a special place.  As for the race, shake it off and try not to cry about the pain to come in 6 days.

June: Mt. Washington Road Race
...and the pain did come.  I spent the 6 days between Ascutney and Washington being a nervous wreck, wondering how I'd handle the pain.  Jesus, this is the most psychologically miserable race I've ever run, and this year I didn't have the benefit of ignorance.  I wanted to improve upon my 1:08:41 (or so) 11th place finish from 2015.  In January I set out with a 1:05-1:06 goal but at the starting line I wasn't sure.  My workouts, and Mt. Ascutney, made me doubt myself.  I ran the same exact first half as last year (well, 5 seconds slower) but felt incredibly limited in my aerobic capacity over the second half.  The pivotal mile for me is 5-- the dirt road section.  It was my slowest in 2015 and this year I ran even slower...30 seconds slower.  I almost quit and walked.  It was a low moment and I questioned my toughness.  Here I was caught and passed by a few guys I thought I could run with.  I rallied a bit for the last mile of this 7.6 mile race but finished in 1:09 and change.  It was good enough for 8th place, which on paper is great for this world-class event, but I knew it wasn't all that.  But still.... a great weekend hanging out with Stoney and a bunch of other high class dudes on a badass mountain.  Dont' forget this privilege, I remind myself.  Matt Lispey's simple mantra has been in my head since we pumped each other up pre-race: "Run as hard as you can on this day."  Yes, that's all you can ask of yourself.
Joe Viger's epic photo from 2015, looking down on the race course. 
I have lots of thoughts about the unique challenge posed by this race, some of which I'm investigating in an honest-to-goodness study of heart rate data from runners in this and other races.  Mostly, I'm convinced that the altitude effects* on this mountain--which in theory are quite real almost right from the start--render all of us sea-level runners hugely disadvantaged to the Rockies folks who show up.

(*I'll have lots more to say on this in a paper I hope to write this fall and I'll post the highlights here. But lots of people seem incredulous that altitude is a factor in this race, so for now, let's get one thing straight: oxygen levels drop linearly beginning at sea level, so in theory, any gain in altitude will have an effect on how much oxygen reaches your muscles.  A controlled treadmill test (link to abstract ) demonstrated that this is true in practice as well.  Runners' VO2-max decreases linearly with altitude, beginning right at sea level. By mile 2.5 or so, a sea level runner at the Mt. Washington Road Race is experiencing a 6% decrease in VO2-max relative to his/her sea level performance, while his altitude- adapted competitors face much less of a drop.  By the last half mile of this race VO2 max has dropped by over 12% vs. sea level values.)

results

July: USA Mountain Running Championships (Loon Mountain Race)

the start. borrowed from http://misquamicutrunner.blogspot.com/
This glorious race, which I've run 4 years in a row now, is hosted by my team acidotic RACING and played host to the USA Champs in 2014.  The start and finish change a bit every year but the meat of the course is the same.  I won't rehash the course description, as my 2014 and 2015 recaps already went over that (2015 report here ), but the race played out similarly to the 2014 championships:  tons of folks sprinted off the line like they weren't running up a goddamn mountain;  I sat in ~30th place, maybe 35th, when we finished the initial climbing and entered the woods portion, on the XC trails;  I held my own in here, not really gaining or losing positions, and was determined to do most of my work when the real climbing began, around mile 3 of this 6.2 mile race.

photo by Snap Acidotic.


My climbing was...about 95% of what I'd hoped.  I had been distracted all week with real-life type issues and I found my focus lagging a bit.  Also, I didn't feel quite as strong as I'd hoped.  At any rate, the result was 20th overall, but a comparison to prior year's races indicates that I ran 15 seconds slower per mile than 2014 over a similar course.  20th is good, and the field was loaded, maybe the most competitive ever, at least up front.  But I did not progress here, nor at Washington, and if you're not going forwards, you're going backwards, as they say.  Had a good run back down the mountain with Mr. Lipsey, who is always good company, to meet an awaiting Wifey for a large and free breakfast at the resort.  Speaking of Wifey, this was to be the kick-off for a vacation week that ended up being rather awesome-- Phish shows (one 2 nights before the race- I hope the mild dancing/shimmying didn't affect my legs?), camping in Acadia, water parks...but I've concluded that racing and vacation are odd bedfellows.  Better to keep 'em separated and that may be the rule going forwards.
Upper Walking Boss, near the finish.  Photo by Joe Viger.

...and why the stalled progress this year with the racing?  (If you've found any of this boring, definitely skip this next part.) As a sometimes-student of running training theory, and ostensibly a legit student of human evolutionary physiology, I believe that training for mountain and trail running can adapt the principles of traditional running training: long run, threshold run, intervals, strength training, cross training, easy days.  The terrain has to change (mostly trails) and the workouts should be run, I think, not on flat ground but on topography that mirrors the event.  So, for mountain races, do threshold runs and intervals uphill.  I have neglected the intervals and I think this has limited my aerobic top end.

results

Taken all together, this has been a super fun first half of my racing year, filled with great mountains, great people, and hard running.  But I demand more of my running than just fun.  I hope that a few minor changes to my training, and improved race-day focus, will help me perform at a higher level for my two late-summer races. I am training to win these races, no less.  I keep saying that I'll get slow at some point, but 34 isn't old for mountain or trail running...I should still have time to get faster.  Onward, to see if that's true, remembering to enjoy the enormous privilege of having the time and ability to test myself in these wonderful places.

Big thanks to the men (and sometimes women) who force me to dig deep, and to my team acidotic RACING for putting on such a great championship race (and generally embodying New England mountain running) and for generously supporting me via some race fee assistance.