Sifan Hassan’s Running Form, London Marathon 2023

Sunday, April 23, 2023, was a historic day in the annals of mid-run stretching. On that day Sifan Hassan stopped twice–once for a brief quad stretch and once to stretch her glutes–and went on to win the London marathon. Let’s look at Sifan Hassan’s running form along with her explanation to understand what happened.

After the race Hassan reported having pain in her left hip, and that much was obvious from the stretches she did. Here’s the footage of her having trouble an hour into the race and stopping to stretch. (The video should start at 1:16:13, with Hassan in the back.)

The Late Left Arm

If you keep watching after the stretches you’ll see a more pronounced version of the asymmetrical armswing she had throughout the race. It’s an unusual type of asymmetry because it’s actually the rhythm of the left arm that’s off, rather than the direction of movement.

Her left arm swings forward late compared to her right arm, and in fact late for any normal armswing. When the arm swings forwards during late stance, it helps the runner perform the whole-body spiraling action that moves their weight forwards and inwards on their stance foot towards toe-off. So a late forward armswing tends to keep the body weight back on the foot, interfering with hip joint extension and coordinated toe-off. The relationship with hip pain is chicken-and-egg: it would either cause or perpetuate discomfort there.

The Forwards Snap

In addition, you can see in this part of the race that the snap in her left arm action is forwards and up rather than down and back as it should be (and as the right arm does). The snapping action shows which direction the armswing is contributing to the runner’s effort.

In healthy running the snap is on the backswing, helping the runner push against the ground. But if the runner’s weight is too far back relative to their foot, the arm snaps on the upswing instead to help lift them off from the stance leg. This is also consistent with some sort of restriction of left hip joint extension for Hassan.

The Pro and Con of Bending Left

Hassan also consistently bends slightly leftwards as she runs. This shortens the left side of the torso (the ribcage and waist) and makes it harder for her to bring her left shoulder forwards to turn her upper body right. This matches up perfectly with the lagging left arm and all the signs she’s having trouble extending her left side.

In fact throughout her track career she’s also done this. It isn’t the usual adaptation to the constant left turns of running on a track, but it may have served her in helping her bank turns better, and she does seem to lean into them exceptionally well.

Hitting the Brakes

If you look from the front, you’ll see she also slightly internally rotates her left foot, reducing pronation and increasing braking forces. Which again makes it hard to get properly over and past her left foot.

And finally, she seems to be pulling her left hip backwards a moment before footstrike on that side, also increasing braking forces. You can look for that during and after the stretching sequence above. You can also see it very clearly when it becomes exaggerated as she takes off for the finish line and keeps looking back to try to figure out why no one else is kicking.

You can see that her left arm is dropped, she bends left, and her left hip doesn’t quite return to balance after each glance back. Turning left to look exacerbates this, but a different runner would come back to balance after each look.

The Backstory

During the race and in her post-race interview she seems to especially be putting her hand on the tensor fascia lata–the muscle on the front outside of the hip joint area. The TFL can act as a hip flexor, internal rotator (opposing the glutes), and abductor (connecting into the ITB). It also can be an area where pain is referred from the hip joint.

Although I don’t know exactly what she was feeling or what her physio diagnosed, if we put together the running form evidence with Hassan’s explanation in her post-race interview, we can make a guess about what happened.

Hassan explained she first felt hip pain 10 days before the race, on her first asphalt run, going downhill. I assume, since this was in preparation for the race conditions in London, that she was also wearing the supershoes she would wear for the race.

The Supershoes: Performance-Enhancing or Performance-Harming?

An effect of this type of shoes is to rock the runner forward onto the toes, promoting hip extension and a long stride. Hassan already had this in spades, but all the evidence I’ve just laid out suggests she’s not as comfortable extending her left hip joint as she is her right. The speed of the extension in the shoes, going downhill, on asphalt, likely caused some alarm in her nervous system, resulting in a protective muscle activation change that of course–as with all compensation patterns–actually created more problems than it solved.

I’ve found that these shoes tend to increase asymmetry in my clients, likely due to the extreme cushioning blocking feedback from the ground. So even though Hassan’s hip extension on the track has been beautiful, any holding in her left hip, internal rotation of her left leg, and excessive braking on that side would almost certainly be worse in whatever super-squishy bouncy castles she was wearing for the race. (In fact it appears they were a legally approved Nike Alphyfly 3 prototype.)

Did Stretching Work?

And so we come back to where we started: the stretches. I advise runners not to stretch mid-run, and one of the consequences of doing so is that you briefly feel better, then quickly find you actually feel worse than before, so you stretch again, and then feel even worse, and ultimately can barely crawl across the finish line. Read the explanation for this phenomenon here.

Hassan’s race suggests that another possible outcome of mid-run stretching is that you might accidentally win the London Marathon.

But how can that be?

Notice how briefly she stretches. The stretch reflex, which tightens a stretched muscle, takes two seconds to kick in. Her stretches are shorter than that, so they don’t activate a reflexive tightening. They are also much too short to cause a decrease in muscle strength and speed. They are, however, just long enough to give some feedback to the nervous system to change activation around that hip.

This is actually a better way to do that, should you find yourself in a similar predicament, though it does take longer.

It doesn’t look like Hassan was terribly successful at solving her problem by stretching. Even in the last few miles you can see her drop her hand to her hip again, and slow-motion footage just after she crossed the finish shows her buckling on the left leg as she tucks her pelvis, glutes failing to fire and upper body swiveling strongly to the right so she briefly loses her balance.

You can see it here when she lands on her left foot with her hands over her face:

Those first few steps beyond the finish line are the moment the curtain is pulled back and you can see whatever the runner has been coping with during the race, and it’s very clear here.

How Did She Do That!?

Runners win races all the time while managing asymmetry and pain. At least 50% of the time I watch a runner cross a marathon finish line, I see them stagger sideways or start limping in the next few steps. Sifan Hassan’s win here is only different in degree–in the intensity of her struggle after the first hour and the magnificence of her comeback. I think it’s unlikely we can attribute her recovery to those few moments of stretching though they might have helped slightly.

The way she seemed to have recaptured her groove as she caught up to the lead women, bringing her left arm better into synch with the rest of her gait, reminds me of the ability Eliud Kipchoge displayed in Boston. Sometimes you win, sometimes you lose, but your chances of being great go way up when you can feel your way out of trouble and into better–if not perfect–balance.

If you’re having trouble with a hip, try this free mini-course to help you get to the cause of the problem and start finding your way out of trouble:

5 thoughts on “Sifan Hassan’s Running Form, London Marathon 2023”

  1. I would agree that the supershoes have pluses and minuses, and it will be interesting to see if over time a correlation with specific injuries does start to occur.

    For a competitive runner, however, they generally offer such an advantage – leaving aside the odd apparent non-responder, Molly Huddle, being one well-documented example – that you can’t afford not to use them. To a degree, there is a parallel, between tennis and the wooden and metal racquets.

    Would your solution be to mostly train in normal shoes and race in the supershoes?

    Second question, and with reference to leaning, have you ever looked at footage of the wonder Eilish McColgan, who has a marked left lean. You can see it here - – but it’s even more marked when she is all out as at 29:22 here –

    • Hi Alan, thanks for your comment. What I’m trying to do here is contribute my clinical experience with runners wearing supershoes to the general knowledge so runners can make the best decision for them. If we let potential benefits alone be the focus of discussion, and talk about downsides later or not at all, then we do runners a disservice. An injury during training or racing due to the supershoes–and an injury profile is definitely starting to emerge–can more than negate any performance benefit.

      • And I don’t think I made it clear enough in my post that I have seen exactly the scenario I hypothesized Hassan experienced happen for several of my clients–all with the left hip.

  2. Thank you for this, Jae.
    I wonder how Sifan Hassan would perform barefoot.
    Same for other elite runners.
    We’ll never know, I guess.

    Thinking of Abebe Bikila.
    Did you ever study his running form?
    Interesting footage available.

    Maybe you can run in almost anything, as long as you are able to adapt.


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