What do we think about step width (SW)?

SW is the mediolateral distance between 2 consecutive steps during running

In this video, we see a very narrow SW
Is this a good thing?
Intuitively, we might feel that it is — that a wider SW is inefficient

But is this really true?

During acceleration, stepping from side to side (‘skating’) has often been seen as a technical fault; and so many coaches attempt to have their athletes step right in front of their hips, feeling that any ‘lateral’ movement - or contact outside the hips - is an error.

Research, however, has tended to show show the opposite — that faster sprinters tend to have wider step widths - at least during acceleration.

“A wide SW may be best suited for developing driving force during ... the acceleration phase, while a narrow step width may be best for ... full stride [upright] sprinting.” - Ito, 2006

https://speedendurance.com/wp-content/uploads/2015/06/changes-in-the-step-width-step-length-and-ste.pdf

Additionally, Sandamas (2020) - in comparing a narrow SW with a wide ‘skating’ style, showed a high correlation between 1st step width and propulsive impulse:

https://www.tandfonline.com/doi/full/10.1080/02640414.2020.1776914

“the propulsive component of the net anteroposterior impulse was significantly smaller for the narrow step width in the 1st stance.” - Sandamas, 2020

But is this only true of the first step?

Not according to @R_Nagahara (2017), who looked at step kinematics through the entire acceleration phase, and reported that ...

https://pubmed.ncbi.nlm.nih.gov/28482364/ 

“a wide SW was interestingly also associated with greater propulsive impulse, particularly in the 13th–16th step section.” - @R_Nagahara

But why is this the case?

Nagahara (channeling Weimann and Tidow) wrote “a wide SW during sprinting possibly induces greater activity in the adductor muscles, consequently contributing to better sprinting performance through greater propulsive force.”

https://www.semanticscholar.org/paper/Relative-activity-of-hip-and-knee-extensors-in-for-Wiemann-Tidow/d60fb2dfae9798cc1773408270c659d2f1df35da

(I’m not so sure about that, and feel it has more to do with spatiotemporal relationships than it does increasing muscle activation — simply, effective acceleration (and upright running) has more to do with appropriate GCT-FT ratios than it does in involving more muscle mass)

As GCT decreases, FT increases - allowing for more time for the body to rotate, and for the legs to reposition fully in front of the belly button.

Concomitantly, SW decreases through the acceleration (from 0.39 ± 0.07m in the first step to 0.17 ± 0.04m in full stride running - previously mentioned Ito paper - 2006)

Remember that sprinting has a significant rotational component — greater flight time allows for greater spinal rotation (rather than the primarily femoral rotation during acceleration), and more time in the air for the lower limbs to fully complete their swing: so narrower step

I like Ito and Koji’s advice from the 2006 NSA paper:

> Sprinters should concentrate on reaching a higher step frequency in the start
> Also - strive for longer steps from the start
> Step width should be maximized during the first steps and then gradually decrease over time

The question then becomes:

Should an athlete purposefully attempt to take wider strides initially, and narrower strides through the acceleration - or should this simply be the outcome of a different kinematic objective? (i.e. projection angles)

UPRIGHT
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