“…She runs like a dragonfly hovering above lily pads on a lake,” was how someone described Letesenbet Gidey’s running form to me on Twitter.
He wanted to know the specifics that create that impression: was there something about Gidey’s beautiful form that was an asset to her successful attempt to set a new 5K world record on October 7?
Here’s the video:
The first thing I thought when I saw Gidey behind the pacer was that she looked like Tirunesh Dibaba, whose 5k record she was about to break. So to help us see what Gidey is doing more clearly, let’s compare this race to the end of Dibaba’s record-setting 5k in Oslo in 2008.
Tirunesh Dibaba’s standard form is to have her upper body quite vertical to the ground, and we see this in her video. She pumps her arms hard–she was kicking harder than Gidey at the same point in the race due to a slow pace at the outset, so we have to bear this in mind as we compare the two.
Regardless, the contribution of Dibaba’s arms to driving her legs is pretty clear. The force in her arm movement and how it integrates with the rotation of her upper body are pretty simple to see.
This upright head and upper body creates a deep lumbar curve, as the pelvis tilts forward in the way it must for this kind of speed. I wrote more about this when I analyzed her form in the 10k in the Rio Olympics.
Gidey’s upper body is, as I mentioned, organized similarly while she runs behind the pacers. Head retracted a bit, upper body near vertical, and eyes downcast.
However as soon as her final pacer stepped away, her form changed. Her head moved forward and her upper body shifted into a slight forward tilt–very different from Dibaba.
I did a bit of looking around at other video of Gidey and I didn’t see the retracted head and upright torso I saw in the earlier part of this race, so it seems those aren’t so typical for her. Being tucked right behind the pacers and running alongside the lights that also showed the pacing may have caused her to pull her head back and gaze downward.
But something important changed when the pacer stepped away–specifically, she was no longer drafting. I wrote about the effect of air drag and how form changes to best cope with it in my London analysis a few weeks ago. A forward lean reduces surface area on the front of the body, thus reducing drag. This wasn’t so important when the pacer Chepkoech was handling the drag (with a noticeable forward lean, though it’s not so clear in the screenshot above) and Gidey was drafting, but the minute Gidey had to push through the air herself, her head and shoulders shifted to push against that resistance and reduce its effect.
If you think back to the last time you walked into a very high wind and recall the feeling of leaning into it, that’s exactly the feeling I’m talking about here. This wouldn’t quite feel like a high wind, and the sensation and adjustment might not be conscious, but the were clearly there.
In addition, in that transition moment Gidey also planned to pick up the pace, and the forward lean serves that goal by allowing a higher backkick.
A higher backkick is exactly what we see in Gidey’s form. Higher than anyone else in the race and definitely higher than Dibaba.
The psoas muscle attaches to the inside of the lumbar vertebrae, runs behind the abdominal organs, and then crosses the pubic bone and attaches to the upper thigh. Just after a runner leaves the ground, when their legs are as far apart as they get in the gait cycle, the psoas is at its longest on the side of the back leg, stretching all the way from the thigh across the front of the pelvis and back in to the spine in front.
The distance the psoas has to stretch at that moment is greater when a runner is upright than when they lean forward. It’s greatest when the pelvis is not allowed to tip forward and the spine is upright, but still farther with a forward tipped pelvis and upright spine than with a spine that’s also tipped forward.
There’s only so far a psoas can stretch. So an upright runner will have a lower backkick than a forward-leaning runner. Hence the difference between Dibaba and Gidey.
But this also leads to a second difference in the legs that I’ve never really seen before: the footstrike.
I never would have said there was anything wrong with Dibaba’s footstrike. But Gidey’s is remarkable. I have seen the difference between what these two women are doing described as the difference between rolling and stepping. Dibaba’s legs have a rolling action, where as Gidey’s legs seem to drop straight down to the ground with the precision of knives.
There’s no shear, no sliding forward or backwards at all when her foot meets the ground. She could probably run across the slickest ice without spikes and look the same as if she were wearing them.
I can only guess at the factors involved. I think one of them is that Dibaba’s upright torso does tend to produce a more rolling leg action as I just said above. I also notice what appears to be more veritcal oscillation (a.k.a. bouncing) in Gidey’s gait, plus her feet are more plantarflexed (pointed) as she approaches footstrike. These are quantitative, not qualitative differences with Dibaba, though.
But they lead me to suspect that Gidey uses more hip joint internal rotation in her running than Dibaba. This is borne out by comparing their thighs as they approach the finish line–Dibaba’s are clearly more turned out than Gidey’s.
Using internal rotation appropriately allows a longer stride length, and indeed that is another asset of Gidey’s. I can’t compare it to Dibaba’s given the limitations of the video, but it’s clearly longer than her pacer Chepkoech, who’s a highly accomplished steeplechaser herself.
So I think Gidey is landing a bit more on her forefeet, has a bit more springiness in her lower legs, has a long stride due to her forward lean and ability to access internal rotation in her hip joints so her pelvis passes her stance foot more before she leaves the ground, and is more aerodynamic due, again, to that forward lean.
Gidey does not use her arms for power the way Dibaba does. You can see Dibaba really pumping, where as Gidey’s arms are brisk but don’t really seem to supply power. They almost seem to be serving the balance function of counteracting the torque from the scissoring of the legs, as the usual biomechanical explanation goes. To a degree I don’t often see–watching mostly road marathons–she’s really all about the legs.
In Gidey’s final laps you can see her head pump slightly forward and backwards, like Mo Farah (to name a notable example). In this case I think it’s because her lean isn’t quite far enough, so her head gets left behind a bit with the push from each leg and has to be accelerated forwards again with her abdominals and chest muscles. This takes some extra work and thus wastes energy, and indeed you can sense the high effort through her whole torso in those final laps. She may not seem to be pumping hard with her arms, but her effort is full-body at that point. It almost seems as if she’s reaching forward with her head for more speed–an excellent strategy. It’s one of the things that makes the video so exciting to watch since it seems just at the very far edge of her ability, like someone leaping and barely catching a branch with their fingertips but amazingly holding on.
Dibaba never pumps her head. As unusual and amazing as Gidey’s lower legs are, the wonder in Dibaba’s form has always been her incredibly smooth forward head movement. I hypothesized when writing about her performance in Chicago in 2017 that this had to do with the side-to-side movement of her upper spine. But she was using her arms in a completely different way, with her hands up near her collarbones. I was surprised to see in this race how different her arms used to be, and I wonder what prompted the change.
In any case, she isn’t using a sinuous side-t0-side movement in this 5k, she’s rotating a lot. But her head still moves the same. My new theory is that this is because of the lift that her spinal extensors provide as part of her upright upper body. This kind of lift dampens impact–I remember learning how to do it so I could rollerblade over really rough streets without getting thrown around back in my wild and crazy 20s.
However she’s doing it, it’s distinctively hers and makes her recognizable even in the most pixellated old videos (luckily!). And it’s dramatically different from Gidey.
I always wonder “what if..” in these analyses. What if Dibaba learned to lean forward, reducing her drag and lengthening her stride? What if Gidey could get that forward lean just right and find some pumping power like Dibaba’s in her arms? These will likely always be hypotheticals, but maybe another runner will come along with equivalent athletic ability and training but these form advantages… and then we might see the next record.
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