Google ngrams for running economy, lactate threshold, and VO2max

I wanted to explore the relative importance people place on difference aspects of running, regardless of how important the really are. So here is a book-indexed trend for each of the terms "VO2max", "running economy", "neuromuscular training" and "lactate threshold".


NB: On an earlier version of this post I had entered "Vo2max" and found a different, erroneous, trend. All sorted out now.

The term "VO2max" has been steadily rising from the 1980s to the early 2000s, where we may or may not be witnessing an ultimate peak around 2005. Though much smaller in book frequency, both "lactate threshold" and "running economy" reached their maximum values in 2002 and have been edging downward. Meanwhile "neuromuscular training" has been growing slowly but steadily. Since as Ngrams only reaches to 2008, I searched Google trends for more recent (search-based) differences.


The trend for these four variables has been quite stable between 2005 to present, with VO2max beating out the others by a fair margin. Therefore I included barefoot running as a more dynamic variable (NB: the phrase 'barefoot running' is quite flat during the pre-2009 ngram timespan). It is interesting to observe the sudden jump in barefoot searches in 2009, followed by a steep decline in 2014 to levels below those of VO2max.

There appears to be some correlation between what is popular in books and online searches (at least for most terms; we should expect that barefoot running will appear in books once more recent data becomes available). Intuitively we might guess that the content of books influences searches, as Born to Run is a likely source of the online trends in barefoot running. But the reverse is now also true; what exists online can influence print. Consider that scientific journals are entirely online, but more importantly becoming increasing accessible to the public while google scholar is quite user friendly. Therefore science publications, nearly always at the forefront of research, when cited directly in websites (e.g. such as Sweat Science), will influence what is written in books.

Only a few years ago the chain of command went something like this:

journal publications => books => online content

As an ever growing number of websites (like this one) are comfortable linking to journal articles directly, online content has switched roles, becoming the source of book content:

journal publications (online) => online content => books

Either way the only trusted source of information remains quality research articles, though blogs may change this in the near future. But for now hunting for the latest research in free-access journals is a good way to find new ideas. So what is popular in running research these days? Perhaps the newest field is the holistic take on running measurements, that no single variable can predict performance but the appropriately weighed combination will. I then searched online for recent articles discussing running economy. Consider this 2014 study on running form:

Eritrean runners have superior RE [running economy] compared to elite European runners. This appears to offset their inferior VO2max. However, the present data suggest their better RE does not have a biomechanical basis. Other factors, not measured in the present study, may contribute to this RE advantage.

And again here:

The dissociation between RE [running economy] and running performance in this homogenous group of [competitive Kenyan distance runners] would suggest that RE can be compensated by other factors to maintain high performance levels and is in line with the idea that RE is only one of many factors explaining elite running performance.

Compare vis-a-vis with a paper from 10 years earlier, with more confident claims: "The importance of RE to successful distance running is well established, and future research should focus on identifying methods to improve RE".

Another modern trend could be to reverse the habit of earlier published studies over-focusing on magic bullet solutions. Hence studies now deliberately question the limitations of adding or subtracting single variables to an athlete's regimen. For instance here:

Our data indicate that women should include heavy-resistance training in their programs, but men should be cautious about using it in season until more research establishes whether certain men are positive or negative responders

Another here:

We conclude incline treadmill training effective for improving the components of RE [running economy], but insufficient as a resistance-to-movement exercise for enhancing muscle power output.

And of course researchers still love to jump on a fad or two themselves, often leading to seemingly contradictory statements:

• Softer and more resilient running shoe cushioning properties enhance running economy [link]

• ...barefoot running improves running economy when compared with shod running [link]

Finally, there is an ever-growing body of meta-analysis such as the fantastic 2013 study on round number marathon times:

We test for reference dependence in a large dataset of marathon finishing times (n = 9, 524, 071)...We provide visual and statistical evidence that round numbers (e.g., a four-hour marathon) serve as reference points in this environment and as a result produce significant bunching of performance at these round numbers

I would be interested to know what other trends anyone else has seen of late.

Final note: There is one more recent theory, known as the central governor, which states the brain controls exercise output ahead of the heart and muscles, and credited to Tim Noakes. However I didn't get any hits when I tried "central governor theory/model" for either the ngram or trends search. "Central Governor" has a trend, but mostly in Nigeria! (hence its meaning is ambiguous in general search engine terms). Either way, CGT is not yet a well-posed hypothesis. Potentially falsifiable, yes, but unclear how to measure, akin to Lovelock's Gaia hypothesis. Might we require people to run on a treadmill inside an fMRI to know what the brain is thinking during exercise. More to the point, it is no long new. Consider the following abstract excerpt from a 2012 paper titled "Is it Time to Retire the ‘Central Governor?"

Over the past 13 years, Noakes and his colleagues have argued repeatedly for the existence of a ‘Central Governor’, a specific brain centre that provides a feed-forward regulation of the intensity of vigorous effort in order to conserve homeostasis, protecting vital organs such as the brain, heart and skeletal muscle against damage from hyperthermia, ischaemia and other manifestations of catastrophic failure...As yet, there is a lack of convincing experimental evidence to support these corollaries of the hypothesis; furthermore, some findings, such as the rather consistent demonstration of an oxygen consumption plateau in young adults, argue strongly against the limiting role of a ‘Central Governor’.

There has been pushback on this paper (much of it led by Noakes himself) but regardless, GCT has been around long enough that it does not appear to be a new scientific framework, rather a shift in one's point of focus from the muscles to the brain. Due to the recursive nature of sport, the real answer lies in the conjoint muscular-mental hypotheses.