Training Tip Tuesday #8- A Look at Running Economy: Part 2

Last week we discussed what (the deuce) running economy is and why it is an important marker for endurance performance. Being able to use our precious oxygen in the most economical way possible is extremely advantageous whether we be racing sprint triathlons or Ironman. Originally I was going to talk about how we can improve RE this week but after further review of the material I've decided to extend this discussion one more week. This week I'll be covering some of the various biomechanical, physiological and anthropometric characteristics that effect RE. This doesn't necessarily mean you should start employing an intervention method to enhance RE. It's simply a sampling of variables that effect RE. NEXT week I'll talk about specific interventions that might help you improve yours. There is one in particular that is easy to implement and carries a host of benefits. Below, I've highlighted a few of the interesting and relevant factors effecting RE. Once again, the Saunders article is my primary source along with some confirmation from various other articles.



Anthropometric Characteristics

I'll place my bet on skinny calves all day long

Since none of us have control over how tall we are, how wide our pelvis is or the size of our feet I'll brush over these factors relatively quickly. The biggest take away is that less body mass on the extremities is conducive to better RE. Small calves are better than big calves when it comes to running fast. This is also part of the reason we wear lighter weight shoes in racing. Less mass at the extremities means less effort to move that mass and less oxygen required.

Physiological Factors

It's generally accepted that a higher percentage of slow-twitch muscle fibers is associated with better RE. We'll touch on this more next week when we discuss specific interventions to improve RE but more running results in an increase in oxidative mechanisms and enzymes. From the Saunders et al., article- "An increase in the respiratory capacity of skeletal muscle permits trained runners to use less oxygen per mitochondrial respiratory chain a given sub maximal running speed." Quite a mouthful I know but the takeaway is this- improving our aerobic energy system makes us more economical.

Stride length

Research has shown that RE is best with a self-selected stride length during running. That is, RE gets worse when subjects consciously tried to shorten or lengthen their stride different from how they normally stride when running. I don't think this has to mean that we should never try to adjust our stride. Most of these studies were done on well trained individuals running at a speed of 8-10 mph (7:30-6:00 min/mile pace. For a well trained runner that is a fairly relaxed pace and they have undoubtedly run hundreds and hundreds of miles at that pace and become very economical. Below we'll discuss the difference between over striding and heel striking. I believe that correcting over striding is a good thing. There is also a difference in whether our stride length comes from in front of us or behind us. If you aren't already running sub 7:00 or 6:00 min/mile pace for a half marathon than don't completely throw the idea of adjusting stride length out the window.

Footstrike

Oddly enough, HEEL STRIKERS were found to have better RE than forefoot strikers! Utterly shocking and utterly conflicting with what is the current day trend of forefoot running. Personally, I don't think HOW the foot hits is the ground is quite as important as WHERE it hits the ground in relation to our center of mass. I will try not to climb on too much of a soap box here but I definitely think this point deserves note. There is a difference between heel striking and over striding. Over striding is bad, heel striking isn't necessarily bad.  I don't think the issue of over striding should be fixed by focusing on what part of our foot touches the ground first but where the foot touches the ground. Many elite runners are known to be heel strikers and I know of at least one extremely successful triathlon coach who actually tries to coach his athletes to become heel strikers.  It's a point worth considering anyways.

Flexibility

No consensus was found on this issue. Some studies found that improved hip flexion and extension resulted in improvement in RE. Many others have found that poor flexibility actually resulted in better RE. This is thought to be due to better elastic return of energy because of stiffer joints, muscles and tendons. My personal belief is that there is an appropriate level of flexibility and that each person is different. Some people are naturally quite flexible and don't need specific stretching exercises to stay that way. Others, I think, can benefit from stretching muscles around the hip that allow them to have full range of motion during their running stride. If tight hip flexors are preventing you from extending fully at the toe off phase of your run stride then you might benefit from stretching your hip flexors.


I want to be careful in mentioning these various variables that coerce to generate running economy. Many of them might seem contradictory. For instance- if a self selected stride length is best then why might flexibility and increased hip extension improve my RE? None of what I've outlined above are interventions that should be taken to augment RE. I will cover that next week. In the meantime I wanted to paint a broader picture of the issue in hopes of eliciting better understanding. Another confounding is that each individual is different with a different physiological, anthropometrical (I just feel really smart typing that word) and biomechanics make up. Even among elite runners there is a wide discrepancy in stride mechanics, muscle fiber type and flexibility. My goal is to educate and elicit thought.

ipsa scientia potestas est

Knowledge itself is power