THURSDAY, AUGUST 10, 2017

My friend Duffy, a former Marquette University cross country runner, has a stride to behold. Running behind him you can see his heels kick up high, seemingly hitting his quads. He runs powerfully, with a slight forward lean. His turnover is quick and fluid.

Watching Duffy turn 75-80 second 400s on the track is like observing a work of art: It gives me the same joy as I found during a private reception at the Metropolitan Museum of Art in New York City when I encamped with a glass of wine in front of Picasso's Starry Night, alone except for a watchful guard, observing the artist's wild, colorful interpretation of a starry night and then, the longer I looked, recognizing more and more of the finely crafted details that make the whole work so exceptional.

Should we aspire to a better stride?

I can never hope to fully emulate Duffy's stride. For a start, he is taller and longer legged. Yet, I think any runner can incorporate elements of the near-perfect stride that Duffy exhibits.

By way of a confession, I am writing about perfecting one's stride because I think I have gotten away from previous elements of my stride that contributed to my past faster times and racing success. I also think the elements of my stride that I have wandered away from helped me avoid injury.

I have taken a deep drive into research on running stride, to see what the evidence suggests about what might be the ideal stride and how to attain it.

Thank me now. I have read the research so you don't have to (unless you really enjoy being a geek runner like me!).

Can The New York Times be wrong?

You may have seen a recent New York Times running blog reference to a new study. It has attracted some buzz, by citing a study of 33 runners, some very experienced, others novice, who by being asked to keep up with a metronome while running naturally on a treadmill were forced to speed up or slow down their stride rate (speed of turnover of legs) and thus also forced to consequently shorten or lengthen their stride because the treadmill speed was constant.

The findings? By measuring how much oxygen the runners required (their "running economy"), the study "proved" the runners of all experience levels became less efficient - meaning they required more oxygen and thus had worse running economy - to sustain the pace whether their stride rate went up or went down.

While the study's author, Ian Hunter, a professor of exercise science at B.Y.U., claimed that the most efficient stride is what comes naturally - "it's built in" - the blog post does note that the study was "a one-time look at a small group of runners and focused on a single, sustainable running speed for each."

Well, runner friends, think about it: If you were asked to run "unnaturally" on a treadmill with a mask on and being forced to raise or slow your stride rate while the treadmill maintained continuous speed, wouldn't you likely be less comfortable and thereby run less efficiently?

Beyond the discomfort of the situation, there seemed to be no thought that one could get used to either faster or slower turnover and thereby gain economy over time. Also, the treadmill did not allow for speed changes, while on the road if we increase our turnover we don't necessarily have to decrease our stride length (and vice versa if we decrease out turnover).

At best, this study is "incomplete science." At worst, it seems to me that the study arrives at an unsustainable conclusion.

The failed one-week makeover

This past May at the American College of Sports Medicine annual meeting a session was devoted to a study entitled "Decreased Metabolic Running Efficiency After One Week Of Practicing Improved Running Mechanics." In this case, seven novice runners were "coached on proper running mechanics and were encouraged to practice employing their enhanced technique for one week." Their running economy before coaching was measured at "50% of VO2max." Then a week later after practicing the better running technique their running economy was measured again. The conclusion? "While subjects reduced their upper body movement and reported working less intensely to run at the same rate with improved mechanics, greater VO2, RER, HR, and MET indicated that, after only one week of familiarization with new mechanics, they were actually running less efficiently."

Conclusive? Hardly. The study authors in the abstract write, "This could be the case because runners didn’t practice the new mechanics sufficiently, or because with any change in running technique, even improvements, temporary lack of coordination due to under-developed neural and muscular control, leads to temporarily-decreased running efficiency. Further research with longer study duration would likely show that increased cadence and decreased upper-body movement result in more efficient running."

Also, who's to say that running at "50% of VO2max" relates to normal running and racing paces?

In citing this study, Alex Hutchinson wrote in Runner's World, "It’s pretty well-established that changing your 'natural' running form will cause you to get less efficient, at least in the short term, as you adjust to new muscle patterns. Whether you ultimately become more efficient once you adjust to the new stride remains somewhat controversial. Many researchers assume this to be the case for well-designed interventions, but there’s not a lot of data out there demonstrating that it’s true, or showing which interventions ultimately improve efficiency and which don’t."

Not that simple

Another set of researchers looked at previous studies that addressed "correlations or relationships between foot strike pattern and running economy."  Of the five studies examined, two "demonstrated a significant effect of foot strike on running economy: One study found that midfoot and forefoot strikers were found to have better running economy compared to rear foot strikers. Another study showed that rear foot strikers demonstrated superior running economy. Three studies showed no significant effect of foot strike on running economy."

Well, wasn't that research helpful? Even the authors of the analysis write, "Further research is needed to discover what particular role or advantages individual foot strike patterns may have on running economy and what other factors and characteristics correlate with running economy and performance.

No benefit - except for D1 runners?

A paper titled "Is changing footstrike pattern beneficial to runners?" reviews a variety of studies and considers the reasons often given for encouraging the majority of runners who have a rear foot strike to switch to a midfoot or forefoot strike - better running economy, reduced ground impact and lower risk of running injuries. It concludes, "based on examining the research literature, that changing to a mid- or forefoot strike does not improve running economy, does not eliminate an impact at the foot-ground contact, and does not reduce the risk of running-related injuries."

Yet, within the paper, we find both the enticing comment that "several studies have observed that the top finishers of short, middle, and long distance events tended to use a mid- or forefoot strike" and a citation of a study of DIvision 1 college cross country runners that suggested that "the occurrence of injuries was reduced in those that habitually used a mid- or forefoot strike compared to a rearfoot strike." The paper's authors said the D1 study "reported a statistically greater incidence of running injuries per 10,000 miles of running using a rearfoot strike compared with a mid- or forefoot strike when the data were combined across sex and level of injury severity or both."

Whether this conclusion would be sustained in the "large, prospective randomized control trials investigating the risk of injury in both forefoot and rearfoot running" that the authors of the "changing footstrike" paper call for is obviously unknown. However, it seems to me if Division 1 runners who run midfoot or forefoot seem to have fewer injuries than rear foot runners, and if top finishers tend to run midfoot or forefoot, foot strike is certainly something to pay attention to.

Reduce your stance time?

Studies suggest that efficiency may be gained by reducing the time the foot is in contact with the ground. On Canute’s Efficient Running Site in "The dream of capturing the force of gravity for forward propulsion: re-incarnations of Pose", the author suggests that while getting faster just by changing from running rear foot to midfoot is theoretically not possible, rear foot runners "who spend too long on stance" but then focus on changing to midfoot strike may find focusing on striking midfoot to be a "useful cue" to reduce the time the foot is in contact with the ground.

Yet, said Steve Magness, Head Cross Country Coach at University of Houston, quoted in an article in Runners Connect by Matt Phillips, "While having a short ground contact time is beneficial, it needs to be the result of transferring force faster rather than trying to get quick with the foot." In short, he is saying that we need to push off, not just pull up.

Injury trade-off

In a Competitor Magazine on-line article, "Is there an ideal running form?", Thomas C. Michaud, D.C., weighs in on the rear foot versus midfoot or forefoot strike question by citing a study conducted in Spain that concluded that slower recreational runners running at varied speeds "are almost 10 percent more efficient when striking the ground with their heels. The benefits associated with heel striking continue until runners reach the 6:25 minute per mile pace."

As for the idea of injury reduction by not heel striking, he observes that "runners who strike the ground with the forefoot absorb more force with their arches and calves, while runners making initial contact with the heel absorb more force with their knees." This explains, he contends, "the higher prevalence of Achilles and plantar fascial injuries in midfoot and forefoot strikers and the higher prevalence of knee pain in heel strikers."

His advice? "If you’re a fast runner and you have a tendency for knee pain, you might want to consider gradually transitioning into a more forward contact. Conversely, if you’ve been plagued by chronic Achilles injuries, a shift to a heel-first strike could reduce your potential for reinjury." Also, "if your goal is to remain injury-free, the easiest way to do this is to reduce impact forces by shortening your stride length and increasing your cadence."

But MIchaud suggests being careful about making significant form changes in a quest to become "fast and efficient." He believes "you intuitively pick the running style that works best for you."

Energy trade-off

Michaud cites research that uncovers the trade-off we make when we shorten our stride to avoid injuries. A shorter stride with increased turnover lets us sustain our speed with up to 20% less ground impact force. However, the cost is that more rapidly "accelerating and decelerating each leg," takes more energy: It "causes the hip muscles to burn so many calories that the metabolic cost of running skyrockets." 

Thus, according to Michaud, anything more than a modest increase in turnover is not beneficial and that's why "a classic study evaluating stride lengths and cadences at different running speeds...showed that experienced runners increase from a slow jog to a 6:45 minute-mile pace by increasing stride length only. After that, faster running speeds are achieved by mostly increasing stride length with only slight increases in cadence."

Ah, that's Duffy!

An intriguing contention from Michaud is that we not focus on reducing impact force but rather on improving our overall form: "Elites prove that it’s not the degree of impact force that does the damage—it’s how you absorb the force...they smoothly absorb impact forces that would break bones in recreational runners by moving their feet, legs, knees and hips with the perfect series of movements."

An important aspect of form is leaning slightly forward at the hips. By doing so, Michaud says, "runners use their upper hamstrings to absorb force that would normally be absorbed by the knee." He continues, "Some great research proves that the world’s best runners make initial ground contact with their upper bodies tilted slightly forward, while less efficient runners contact the ground with their spines almost vertical."

Summing it up, in "Is There an Economical Running Technique? A Review of Modifiable Biomechanical Factors Affecting Running Economy," Isabel Moore concludes from analyzing available research that running economy is optimized by "using a preferred stride length range, which allows for stride length deviations up to 3% shorter than preferred stride length; lower vertical oscillation; greater leg stiffness; low lower limb moment of inertia; less leg extension at toe-off; larger stride angles; alignment of the ground reaction force and leg axis during propulsion; maintaining arm swing; low thigh antagonist-agonist muscular coactivation; and low activation of lower limb muscles during propulsion."

Translation: Perfect form. That's Duffy!

Unexpected gem

While we are focused here on form, I can't pass up a clue Moore offers about running faster.  She writes, "Extrinsic factors associated with a better running economy were a firm, compliant shoe-surface interaction and being barefoot or wearing lightweight shoes." 

In looking further, I found an analysis that addressed the interaction between shoes and running economy, The effect of footwear on running performance and running economy in distance runners. This research reviewed studies that "reported significant, but trivial, beneficial effects on running economy for comfortable and stiff-soled shoes...a significant small beneficial effect on running economy for cushioned shoes...and a significant moderate beneficial effect on running economy for training in minimalist shoes." Analysis across studies "found significant small beneficial effects on running economy for light shoes and barefoot compared with heavy shoes."

Perhaps of greatest importance, the analysis found "a significant positive association between shoe mass and metabolic cost of running" and that "footwear with a combined shoe mass less than 440 g per pair had no detrimental effect on running economy."

What shoes are you running in? One shoe model I now have in rotation are a pair of Saucony Freedom ISOs that at size 9 weigh 510 grams (18 ounces) for the pair. Close to the "no detriment" weight, but not as close as my other shoes in rotation, ASICS DS Trainers that at size 9 weigh 454 grams (16 ounces) per pair.

Complex and individual

Back to our primary topic, the ideal running form. Perhaps the most instructive thinking about form comes from researchers Kyle Barnes and Andrew Kilding in "Running economy: measurement, norms, and determining factors." Their exhaustive look at many studies of what promotes the greatest running economy lead them to three conclusions:

1. "Running economy is a complex, multifactorial concept that represents the sum of various metabolic, cardiorespiratory, biomechanical and neuromuscular characteristics during submaximal running."

2. "Many of the determining factors of running economy are able to adapt through training or other interventions, however an economical change in one athlete may be uneconomical in another athlete because of differences in other physiological or biomechanical characteristics."

3. "Representative running economy values for different caliber of runners running at various speeds are presented."

My reading of their findings? You must make variations in adapting all of the research on what makes for great running form to your individual situation. Like Picasso painted Starry Night, put it all together so that the whole of your running form is your own unique masterpiece.

Style matters, at least to me

As for me, I can't and shouldn't fully emulate Duffy, but I have shortened my stride just a bit, upped my turnover 3-5 strides a minute to near 170 and am working on a little stronger push-off. Whether that's why I was a minute faster in the 8K cross country race this past Sunday than I was a year ago and why my closing mile was as fast as I have raced recently remains a question.

In any case, I did like what my runner friend Tom said to me after watching me finish the race: "You looked great out there!"