Quoted post said:Originally posted by beerco
Power contribution can be dissected into it's vectors as Taras stated.
Simply put, the power provided by Ankling is going to be the amount of force provided by the ankle at the pedal, times the distance moved by the toe as a result of ankling, over the time it took to do so.
All you need to do now is calculate it.
Quoted post said:Power contribution by Ankling is therefore force from ankling (probably quite difficult to measure independently) times the 4 to 6cm of movement over .5s.
I imagine that this is a very small number of watts
This can be calculated (non trivial mind) - they did it in the study and it wasn't small. In fact, the assumption you make above is where you and the study may have slipped up!
I've just ploughed through the study-speak so I'll tell you what they did.
They calculated all instantaneous joint angular velocities(via analysis of a film of pedalling). They recorded all pedal forces, estimated the weight and moment of inertia of each leg segment then solved equations to calculate the torques at the joints. Scary stuff to the innocent bystander but pretty standard.
To estimate the power generated by the muscles surrounding each joint they multiplied angular velocity of the joint by torque on it. As you suggested.
So they seem to have discounted the mechanism I was discussing with Taras000 ie that the gastrocnemius can torque the ankle open by transfering thigh power and none of it's own.
They sort of address this point by claiming that it is likely to be the soleus that does the great part of any positive or negative work at the ankle.
They also say "the possible coupling effect of the gastrocnemius and other 2-joint muscles [...] might influence power output and needs investigating further.
Quoted post said:Now, this doesn't mean that your calf isn't in a strong, ATP consuming isometric contraction the whole power stroke, it just means that it's not being translated into power propelling you forward (i.e. the energy is spent fixing the pivot point).
Oh, I may have got you wrong earlier.