Running Economy

The concept of running economy (RE) – the amount of oxygen our body uses at a given speed and distance – is akin to fuel efficiency in a car.  If we have a heavy car, with a big engine, going up a hill or pressing the pedal hard as the light turns green, our fuel economy suffers.  So it goes with running.  Ideally we’ve got a trim chassis, run with an even pace, lean easily into the hills and then motor down them.

Most books on running devote space to this topic.  Pete Magill, Jordan Metzl, Owen Anderson, and Tim Noakes come at it from a slightly difference angle.  However, for the endurance runner it boils down to what percentage of the oxygen we have at our disposal is being used to move us forward at a submaximal pace.  Other than a finishing kick this is the pace we run.  While VO2max gets a lot of attention, RE is crucial.  Many highly successful runners have respectable but not top-end levels of VO2max.  Frank Shorter, for example, had a 72% VO2max but regularly beat competitors with 80%+ levels.  RE is closely related to the concept of fatigue resistance, which Anderson defines as “the ability to sustain a high-quality velocity for an extended time without a falloff in pace or intensity.”  We’ve all encountered runners who seem to glide along while we are pushing our limits (of course they may be doing a good job of hiding their discomfort!)

Training improves both RE and fatigue resistance.  Mileage, speed, hills, strength work, stretching and good form support both measures.  To be sure, there is also a genetic element involved, though genes seem less important with RE than VO2max, for which improvement is fairly limited.   Running form bears close attention, as inefficient biomechanics leads to wasted energy.  A commonly cited example is heel striking.  Ideally, when our foot contacts the ground it is near or under our center of gravity enroute to toe-off and forward movement.  However, when first contact is with the heel, there is momentary braking, seen with a slow-motion view of one’s gait.  It’s something like continually tapping the brake pedal when driving.  We may not feel a jerking, but we’ll certainly notice the effect on our gas mileage (and ultimately in our brake pads!)

At first blush, it seems RE should decrease with age.  Everything else does!  But the research does not support this.  Yes, older runners slow down, but it’s due to a decline in the various components of RE that drive this. Confusing, perhaps. Recall that RE is an efficiency measure, not the measure itself.  If one person drives a Prius and at best gets 55 mpg and another drives a Honda Civic, topping out at 40 mpg, the Honda driver getting 38 mpg (a 95% efficiency) has a higher RE than the Prius driver getting 50 mpg (91% efficiency).  A 2011 study led by Tim Quinn from UNH compared RE in runners under age 40, 40-59, and 60+ at four speeds for five minutes between 10:00 and 6:40 min/mile pace, which for all the runners was a submaximal pace.  They showed similar RE for all three groups.  Not surprising, the % of maximal VO2max attained was highest in the oldest group.  Meaning to run 6:40 pace, the oldest group had to use more of their capacity.   Measurements showed the older runners had decreased flexibility, muscle strength, maximal heart rate, and VO2max compared to younger runners.  No wonder they had to work harder!

Of course this is hardly new news.  We know our top-end VO2max is in the rear view mirror.  And we already know we have to work harder than the 30-something next to us to drive the pace in a race.  Thus, it comes back to doing all we can to get as close to 100% of our reduced potential as possible, with smart training (including long runs, hills, intervals, and striders) and proper rest and training periodization.  These are things under our control.

Bottom line, we put a lot of time into our training and want to be at our very best on race day.  Let’s make sure we prepare well, fill our tank with good fuel and not be tapping the brake.  And thoroughly enjoy it, even if it feels harder, to go slower! 

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