Tigst Assefa Berlin Marathon 2023 World Record Running Form Analysis

On September 24, 2023, Tigst Assefa flew through the Brandenburg Gate towards the finish line of the Berlin marathon, startlingly fast even at a glance; stunningly fast according to the clock.


I can’t speak to all the factors involved in her performance. However I can speak to her running form and what it suggests.

Assefa’s form in Berlin in 2023 was strikingly different from the previous year, and the differences grow when we compare the videos. In the absence of any indication she’s done form work or some kind of highly effective physiotherapy, and knowing she wore different shoes this year, I think we can assume her differences in form are an effect of the shoes.

Here’s a video summary of the differences I see. Read on below for a discussion of each.

More Arched

Assefa’s form change this year is similar to Brigid Kosgei’s form change in 2019, when she raced in supershoes for the first time and set the previous world record. I’d captured slow motion video of Kosgei in the 2018 London marathon in racing flats, and when I filmed her in Chicago I at first didn’t even realize she was the same person, her form was so different. She was more extended overall, with her pelvis tilted forward and shifted forward, and her back subtly arched, with chest slightly lifted. Her arm action was unchanged, but everything else was fundamentally different.

The same is true of Assefa this year compared to last, except she was in supershoes last year as well. Just not the brand-new super-light rocker-sole model she wore a few days ago. These screenshots show the difference:

While Kosgei had been actually a little too flexed before she strapped on supershoes, that wasn’t true of Assefa. She had a great balance between her flexors and extensors last year, so she had a nice, clean lean. This year that has disappeared, and now she’s a little arched, with her head back.

In my experience, this change to a slightly extended form can be produced by a rocker sole that causes the runner to take off from farther forwards on their toes than they otherwise might. This also results in the hip joint being farther past the foot than it otherwise would be requiring more hip hyperextension and usually also more anterior pelvic tilt. If it requires too much, the runner will arch their back rather than leaning more deeply to avoid any danger of faceplanting. Both Kosgei and Assefa did this in new footwear.

One might be tempted to argue that this slightly arched posture must be good for fast running, given the race results. But it actually restricts the airway by taking the runner out of atlanto-occipital extension, and that most definitely is not good. It appears to also reduce the amount of force a runner can put into the ground in late stance to push off.

In actuality, this form change simply indicates that something about the rocker in this year’s shoes is different and having a bigger effect. I don’t know the details, except that the manufacturer trumpeted its innovativeness in a way that suggested it was longer than earlier versions. Longer would make sense for this form change.

Another reported element of the new shoes that plays a role here is the significantly lighter weight. Heavy shoes tend to promote a forward lean, as the runner works to pull the feet forward. To understand this phenomenon, imagine you’re trying to run in quicksand. As you try to lift your foot from the ground and feel it resist, you lean away from the foot to use your weight to try to pick it up. The same pattern applies to the weight of shoes.

There are a lot of good reasons to lean forwards when you run, with the reduction of drag (or air resistance) key among them. So I’m not saying Assefa was leaning forwards last year to deal with inordinately heavy shoes. But since this year’s shoes were so very light—lighter even than old-school racing flats—they provided less need to lean forward even as the rocker triggered arching. To me, this suggests the change in weight was significant enough for her to alter her movement.

Less Pounding

Last year Assefa’s head and upper body action was very active–almost pumping. There was obvious tension in her neck (her sternocleidomastoid muscles standing out sharply) and, when seen from the front, a kind of noisy side-to-side action that was difficult to specifically trace but seemed connected to her obvious right/left asymmetry.

Comparing that footage with this year, it suddenly also seems clear how much impact carried through her body to her head. I don’t consider that a bad thing, though again, the noisy action (meaning many conflicting muscle actions occurring together) and tension in her upper body suggested a lot of extra effort.

That seems clear in comparison because you just don’t see the impact this year. There’s still some tension, a bit of a forward/backward bob… it’s not Kipchoge’s smooth bounce. But there’s a shock in each footstep in 2022 that’s gone in 2023.

That could actually be bad for performance, because if you don’t compress the spring, it can’t spring back. Impact drives running when properly channeled. But whatever impact was missing this year was likely made up for by the longer rocker providing propulsion.

Higher Cadence

Looking at the side-by-side video above, it’s clear that Assefa’s cadence or stride rate was higher in 2023 than in 2022. That defies the typical phenomenon of a slower stride rate due in supershoes due to the large amount of foam. However lighter shoes could help with this, and it’s possible an amped-up rocker in the shoes could as well. A higher cadence–more footsteps per minute–obviously contributes to faster running, especially since her stride length doesn’t seem shorter, though with the differences in the video angles between the two years that’s hard to measure. If anything, her stride length almost looks longer than before.

Overall it’s clear from changes in Assefa’s form that her shoes were affecting her differently from last year’s shoes, and given the magnitude of her world record it’s pretty unlikely that effect was negative. I can’t put a number on the benefit she got from them, but it looks real to me. Sadly, that means I don’t know who got the world record: Assefa or Adidas.

Wondering who I am and how I’m qualified to do this analysis? Read this.

18 thoughts on “Tigst Assefa Berlin Marathon 2023 World Record Running Form Analysis”

    • Thanks, Matthew. Yep. Supershoes make me want to stop paying any attention to the roads and track, and just watch trail races… except I think Jim Walmsley won the UTMB in new trail supershoes, so I’m feeling not quite sure where I can turn to enjoy a sport that’s still about human athletic accomplishment rather than superior equipment.

      • Well I’m very glad I didn’t give up on the sport when innovations such as fiberglass pole-vaulting poles, foam pits, and synthetic tracks were introduced.

        I suppose we started down this slippery slope when the first athlete to wear sandals showed up on the starting line. So should we require everyone to race barefoot? Or land in sawdust? (The result of that would be a lot of high jumpers with broken necks.)

        Despite today’s obsession with records, the sport is still mainly about competition and always will be.

        • The comparison of the supershoes in running to equipment in most other sports isn’t right. There’s no pole vaulting without a pole, no cycling without a bike, no skiing without skis. Those are equipment sports. Doesn’t mean the equipment can’t be controversial, but it is part of the sport.

          Running is not an equipment sport. It’s one of the very few sports that can be done with no equipment at all, along with swimming, walking/hiking, and jumping. There’s gear, for protection, but it’s not equivalent to the pole in pole vaulting.

          And the real problem with these shoes, as Ross Tucker has so clearly expressed, is they benefit different runners differently, changing the outcome of races in an unpredictable and difficult to assess way.

          That’s why I did this analysis–in an effort to identify the effect of her newest shoes even though I can’t quantify it. I’ve been helping runners improve their form for over 20 years, and I’ve seen many of my clients in several different pairs of shoes, so I have a pretty informed eye for the effects of footwear.

          • Yes, of course you can’t pole vault without a pole. But before fiberglass poles, there were steel poles. And before steel poles, there were bamboo/wooden poles. And so on.

            Running shoes have, of course, evolved in the same manner, with the changes made to improve performance as well as prevent injury (which itself is performance-enhancing).

            So in that sense, yes, running IS an equipment sport. I think it’s safe to say that Kelvin Kiptum couldn’t possibly run 42.195 km in 2:00:35 without shoes. And he probably wouldn’t even have made it to the starting line if he had run 300 km/week, which is reportedly the training volume he sometimes hits, without shoes.

          • “And the real problem with these shoes, as Ross Tucker has so clearly expressed, is they benefit different runners differently, . . . ”

            I haven’t read Ross Tucker’s take on this (I’ve seen others refer to it), but it seems odd that the super shoes would preferentially benefit E. African athletes. I can’t think of any non-African athletes whose times have improved as dramatically as those of the Kenyan and Ethiopian athletes, at least at the marathon distance.

  1. Assefa certainly deserves all the credit (well, she and her coaches) for her astonishing WR. After all, there were no doubt others in that race who were wearing the same shoes.

    • Thanks for your comment, Drew. No doubt that Assefa trained and ran–I’m not saying the shoes ran the race for her! But her finishing place and time are impacted by the shoes, and that’s the question here. Others in the race *did* wear the same shoes, but because different people respond differently to the same shoes, that’s not relevant to whether they made the difference in Assefa’s performance. Some of them would have been helped by the shoes, others (as the research on supershoes in general has shown) would actually have run worse in them, and still others probably ran the same as they would have in regular shoes. That’s why it’s worth trying to determine their effect on Assefa.

      • Sure, it’s fine to speculate about the effect of the shoes on her form. But I wouldn’t completely dismiss the effect of training as the cause, either. As you well know, the extremely repetitive nature of distance running enables us to reprogram our motor patterns fairly quickly with training.

        And Assefa didn’t start training as a long-distance runner, let alone marathoner, until 5 years ago. Before that, as a junior, she was a world-class 800-meter runner (1:59!). So it seems entirely plausible that last year she simply lacked the strength to maintain efficient form throughout the race, even though — or maybe because — she ran 2:15. Slouching forward is something many runners do when they become fatigued.

        • Drew, see my responses to your earlier comment above, and also to Will’s. It’s not true that her form is better in 2023, and for that matter, it’s not true that efficient form takes more strength than worse form. Efficient form requiring more strength than inefficient form would be a contradiction–if it’s efficient, it requires less work, not more.

          That’s why form is often better when a runner starts to fatigue. They don’t have enough energy to continue trying to implement faulty ideas and depend on inefficient movement habits. They get more efficient in their overall movement.

          The forward lean Assefa had in 2022 wasn’t a slouch. Her back wasn’t rounded. It was just a good lean. Arching is less efficient, and the fact she was doing it in the newer shoes, and all the way to the finish line, suggests to me that it was produced by the shoes. Especially since, as I said in my post, Brigid Kosgei underwent the same form change when she switched into supershoes. And also, since writing the post, it occurred to me that Mary Keitany also showed this change in form towards the end of her career. She was a Nike athlete, I believe, and probably started wearing supershoes before they were publicly known, as all the top Nike athletes did. And that’s about when her form changed. It was perplexing at the time, but if I’m remembering the timeframe correctly, it now makes sense.

          Of course not everyone responds to the shoes that way, and maybe not every model of supershoe promotes this kind of form. After all, Assefa was also in supershoes in 2022, just different ones. So it’s not the category of shoe, it’s either specific shoes or specific athlete-shoe interactions.

          • “The forward lean Assefa had in 2022 wasn’t a slouch. Her back wasn’t rounded. It was just a good lean. Arching is less efficient . . . ”

            Has anyone published any data that support the idea that leaning forward results in better running economy than running with a more upright posture? I would genuinely be interested in reading any such report.

            Seems like this would be fairly easy to test, because running economy can be quantified as the amount of oxygen consumed per kg body weight at a submaximal pace.

  2. Could these bio mechanical differences simply be explained by the difference in speed and overall fitness between last year (2:18) and this year (2:11)?
    Also, this video is filmed near the finish, when the 2023 athlete was running at fastest during entire race (not same speed as 99% of the race).
    I agree with everything you observed,

    • In my experience, Bruce, the arched back isn’t something that happens as a runner gets faster through training, it’s something that happens as the amount of hip extension they can tolerate gets challenged. I have seen that happen to runners after they get off a long plane flight, but in that case their performance is wretched compared to their ability and past performances. It’s a very negative effect. I’ve never seen it make anyone faster except as an effect of wearing supershoes (in which case it’s other aspects of the shoes creating the higher speed, not the posture).

      The change in impact could only be the footwear or running surface, and as far as I can tell there’s been no change to the roads in Berlin. I’ve never in 20 years seen a runner simply make a form change like that.

      The cadence could be a result of her simply running faster. It doesn’t *have* to be the shoes. However it does defy the trend of supershoes reducing cadence, and that’s very interesting and makes me speculate that these shoes are different–at least in terms of how Assefa responds to them.

      As for the choice to look at the video near the finish, it was more practicality than anything else. The camerawork is clearly choreographed for this stretch of the race, reproducing nearly the same angles from year to year, so it made comparison from multiple angles much easier for me than hunting through the rest of the race video for analogous shots. But that said, for evaluating form the more significant question is how hard she’s running rather than how fast she’s running. That’s pretty comparable–enough so to make the comparison anyway. And again, impact and posture would not be that different at a slightly lower speed. Only cadence might.

  3. Re the last question asked I agree that effort and comparable camera angles are important but wouldn’t we expect form to potentially deteriorate over the course of a marathon? Is the 2022 form at the start of the race more similar to the 2023 form at the end of the race? Ie. could increased fitness and core stability/ strength allow Assefa to hold better form for longer?

    • Will, you’re assuming that Assefa’s form is better at the end of the race in 2023. It isn’t necessarily. The slightly arched back is not better form, and the reduced impact can only be caused by footwear, in my experience. The increased cadence is just faster without being better or worse from a form perspective–since her cadence wasn’t problematically slow in 2022, we wouldn’t necessarily call it an improvement. It’s just how she’s running faster, and could be the lightness or springiness or rocking of the shoes, or theoretically just that she’s less tired, so that could be better fitness. Can’t be sure.

      I did, however, go back and compare the two races at 20k, and the differences are still the same, including the cadence difference. The only thing that’s slightly different from the end is that Assefa is not quite so arched at 20k in 2023 as she was towards the end.


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