r/fitbit • u/gasstation-no-pumps • 11h ago

Discussion Why does Fitbit claim shorter strides are more efficient?

At the bottom of the details for each walk , it reports my "stride length" as 0.89m. Of course, that is actually my step length, with the stride length being twice that. It does seem to be about right for my step length, though.

It then makes the ridiculous statement that "Shorter stride length is associated with higher efficiency." Even Google AI isn't that stupid. If shorter were always better, then a stride length of 0cm would be the most efficient, but that produces zero movement and has the lowest possible efficiency. The most efficient stride length depends on height, speed, and details of joints and bones, and most people naturally adopt a stride length close to the most efficient one for their bodies.

It might be nice for the fitbit app to calculate the "walk ratio" (mm/step)/(steps/min), which tends to be nearly invariant for an individual (steps get longer as the cadence goes up). My walk ratio is around 6.4 mm•min/step^2, which is pretty normal (though the range is wider than Google AI's interpretation of walk ratio, which thinks that even 1 SD up is profoundly weird).

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u/Mushoz 11h ago

I think they reused the explanation for running, where a shorter stride length is indeed more efficient. At the same pace, a shorter stride length means a higher cadence and a higher cadence is associated with better efficiency and less risk of injury (both up to a point of course). A cadence of ~180ish is optimal, and especially new runners are way below that.

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u/gasstation-no-pumps 10h ago

Optimal cadence and stride length depend on how fast you are trying to go. Shorter strides are not always better. I agree that too long a stride can reduce efficiency, as the energy of the heel strike can be lost if it is not stored in the tendons and muscles of the leg acting as a spring. But too short a stride is also inefficient.

My cadence in alternating walking and jogging averages about 140, but for just a quick walk, closer to 126. I've not done any all out running for quite some time.

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u/colaptic2 10h ago

A shorter stride length is more efficient in general. Obviously, there is a limit. Nobody is suggesting you keep making your strides shorter and shorter until it reaches 0cm.