timbasile wrote:
codygo wrote:
In running, one could have stride length differences, and other kinematic asymmetries at hips, knee, and ankle joints. If the leg with a Stryd sensor is left “dead” and one hops with the other leg, what would it report? There’s assumed symmetry and the errors are likely to be
more severe than single-sided cycling power meter measurements since there are more degrees of freedom to go wrong.
Even the dead leg needs to travel the same distance in the same amount of time as the dominant leg. You might have differences in stride height if you're dragging the dead one around, but stride length needs to be equal between each leg.
What doesn't change also is your weight - the two leg system still has to run your body a set distance, over the same hills, against the same wind, etc.
The thing is, it
does not travel the same distance. Only in a crude bulk measurement owing to it being stuck to one’s hip is that statement meaningful, but if we consider the thigh and calves to have their own center of mass, and trace the distance of those centers of mass along with rotations and respective velocities, then we see they are not the same.
The (implicit) assumption here is that energy is conserved, but that is not correct. If one takes a leg in state A and move it to state B, one does not know anything about the power or work required to change states because internal work is not conserved, and what we care about is metabolic power. One needs to know, or reasonably estimate the path the leg took to change states, along with the velocities along that path.
Imagine someone running while having to clear an arbitrary set of hurdles or water puddles, only with their un-sensored leg, while the other side with a sensor performs a standard running gait. Surely both legs are still attached at the hip, but now one leg is performing an extra unmodeled movement or exchanging momentum to something that isn’t solid ground.