What if the entire effect of "super" racing shoes was increasing stride length by one inch?
It's gotta be something like that
As “supershoe” distance-running technology tailored for competitive environments permeated first the world-class road scene (c. 2016) and then the world-class track scene (c. 2019)—with regular citizens gaining access to each type of new racing flat within a year or so of the pros first sporting them—most of the discussion on how they helped runners become faster focused on how they improved running economy. That is, their practical effect—often advertised as being 4 percent for the road-racing models, at times even higher—was to allow a runner to achieve a faster time with precisely the same level of power output.
What I haven’t seen, mainly because I haven’t looked everywhere or really anywhere, is precisely how the effect is manifested in the basic equation average stride rate times average stride length equals average speed. If a runner suddenly improves his time without the perception of having changed anything, then either his stride rate is increasing, his stride length is increasing, or some combination of both. (It’s possible to conceive of a scenario in which one variable decreases while the other overcompensates, but this is unlikely.)
It seems as though a runner would notice, or at least be capable of noticing, an incremental increase his in turnover (stride rate) during a race. But perceiving a small change in stride length is probably trickier even when trying. The mind can seize on a regular rhythm as a reference point, even unconsciously, but the mind has no referent for small variations in stride length.
Also, it would seem that the construction of these shoes is designed to increase stride length, at least the track models. The road shoes seem to act through some combination of increased “springiness” and the unprecedented ability to safeguard the infrastructure of the power plant itself, i.e., keep people’s legs from being so bashed to jelly that neither ample fitness nor ample glycogen stores can keep them from slowing late in a long race. That is, Nike’s Alphafly and Vaporfly road models evidently prevent the body’s mechanism for processing the raw ingredients within from being compromised.
Not only that, but it seems as though if any shoe is capable of altering stride rate, it would do so by forcing a change in mechanics that would primarily affect stride rate anyway. I can’t even conceive of a way a shoe could compel a higher stride rate while changing nothing else unless they emitted beeps at a preset cadence, like those annoying Casio “pacer watches” from the 1980s that the Federal Trade Commision should have banned before any of the patents for these devices were even cobbled together.
Finally, formal evidence that this happens exists in the ever-embattled scientific literature.
Pretend that the only effect on the average wearer of each type of no-longer-new racing shoe is to increase stride length by one inch. (The delta with these things seems to be sizable; some people don’t like the Vaporflys at all. I think those who naturally push less off their forefeet gain more than others do, but that’s for a different heap of steaming suppositions.)
The following examples are fraught with inherent problems. A major one is that virtually no one races a marathon while keeping stride length and stride rate remotely constant (considering a 10-percent variation on either parameter to be significant). A metronomic, almost kickless Jakob Ingebrigtsen-style all-out mile effort keeps the values of each parameter closer to constant, but both numbers still wobble a little in practice. But working with averages will suffice, and if we* focus only on truly fast runners, that weeds out much of the noise creating by huffing shufflers like us. And either way, none of this affects whatever the primary effect of the shoes is.
So, with my model thus established as workable and any of your complaints about it irrelevant:
Imagine you were capable of running exactly four minutes for the mile in pre-2019 track spikes, at a steady turnover of 190 steps per minute. At this tempo, it would take you 760 steps to cover the distance. 1 mile = 1,760 yards = 5,280 feet = 63,360 inches. Your stride length in an all-out mile is therefore 63,360 inches/760 steps = 83.37 inches per step.
If “superspikes” added exactly one inch to your stride, your new stride length would be 84.37 inches per step. This is an improvement of 1/83.37 = 1.20 percent. If nothing else changes, you therefore get to the finish line of the mile 1.20 percent sooner.
A 1.20 percent improvement to a 4:00 mile = (0.012)(240 sec) = 2.88 seconds. Suddenly, you’re 3:57.12 miler.
Now to the bozo ranks. Assume I raced my fastest marathon (2:24:17 in April 2001 at the Boston Marathon) at an average stride rate of 180 steps per minute, or 3 steps per second. 2 hours, 24 minutes, and 17 seconds is 8,657 seconds. Under these assumptions, I took (3)(8,657) = 25,971 steps in this marathon, not including those into and out of a box of plastic containing significant amounts of human excrement planted near Coolidge Corner.
A marathon is (26 miles x 63,360 inches/mile) + (385 yards x 36 inches/yard) = 1,661,220 inches. I therefore averaged 1,661,220/25,971 = 63.96 inches per step in what was for me a Yo, man! effort.
An improvement of 1 inch per step is a fractional improvement of 1/63.96 = 0.01563, or 1.563 percent. An improvement of 1.563 percent to a 2:24:17 marathon results in a 2:22:02. That’s two seconds slower than the U.S. Olympic Men’s Marathon Trials standard was for the 2004 cycle. But even had this hilarious “‘supershoes’ just for me fifteen years in advance” scenario unfolded, the qualifying window for the 2004 Trials didn’t open until January 1, 2002 anyway.
Finally, if it’s close to true that most runners receive the same one-inch boost—or whatever the number is—regardless of ability, then it makes sense that slower runners stand to gain more from these shoes than faster ones. If a four-hour marathoner has the same average stride rate as a world-class male marathoner, his stride will be only about half as long, so he’ll pick up twice as much time percentage-wise, and therefore more than twice as much in total seconds, than an Eliud Kipchoge type. A world-class marathon runner is already blessed with a hell of a stride, so any tweaks to a two-hour type will be more marginal.