Knee/Torso angle vs Power output in TT / Pursuit

InPursuit

I am researching optimum positioning for road TT & Track Pursuit events and wanted to know if anyone has done fact based trials on effects of knee / Torso angle on power output. The only research I have seen does not show any variation in power output (max or mean) for knee angle of 145 - 155 which seems odd as I would have expected a rise in output when angle is increased to 155.

I am also interested to here from guys (or girls) who compete in multiple disciplines in order to know what changes they make to knee angle (by change in saddle height) for various road & track events. Primary interest is to see if knee angle is reduced for long events such as road race due to hamstring tightness and higher for shorter events such as TT or Pursuit in order to maximize power output.

chrisw12

Do a search/ask on slowtwitch, they're big on all that angle stuff over there, can I say that they were the pioneers of the rotate the body around the bb to preserve the hip angle?

Out of interest why and how do you think MAXIMAL knee angle would change DURING an event?

P_Tucker

chrisw12 wrote:

Out of interest why and how do you think knee angle would change DURING an event?

Pedalling.

InPursuit

chrisw12 wrote:

Do a search/ask on slowtwitch, they're big on all that angle stuff over there, can I say that they were the pioneers of the rotate the body around the bb to preserve the hip angle?

Out of interest why and how do you think MAXIMAL knee angle would change DURING an event?

I have researched it extensively and so far have not seen anything factual in terms of power gained (%) for a 5deg change in knee angle.

I know pro level track guys change their seat height for various events - I assume the reason is max power vs hamstring - the theory is that a knee angle of 155 would enable you to reach max power but hamstring flexibility/tightness will determine if you can hold such an aggressive position in an endurance event. Basically the longer you cycle the tighter your hamstring will get so a cyclist might set their knee angle to 145 for a 4 hr road race 150 for a track endurance event (points race) or road TT and 155 for a pursuit event.

Another consideration is that a change in seat height does not necessarily translate to a change in knee angle when talking about TT & Team Pursuit as one would be sitting on the saddle nose so if you left the seat height the same between your road and TT positions the result would be a smaller knee angle - to compensate you would raise the saddle by 10 - 15mm just to hold the same knee angle.

To complicate the matter even more there is muscle adaptation that might also play a factor in the test result - for sure i know of atleast one elite cyclist (raced at 2008 Olympics) who developed cramps when they changed their bike (& position) shortly before olympics - his mistake was starting off too hard in the new position and not allowing himself (his muscles) enough time to adopt to the new position when he started training on the new bike.

chrisw12

Ok I'm miles away from being an expert in any of this but here goes.

I understand that changing seat height can change MAXIMAL knee angle but in all your paragraphs above you don't mention the ankle joint. Wont the rotation of the ankle joint retain the optimal knee joint angle whatever the seat height?

What I'm saying is, when varying seat height, what does the body preserve, optimal ankle angle or optimal knee angle.


I said go on slowtwitch because the standard joke on there when people ask for position advice is 'your seat's too high' to which someone sometimes reply's with 'no' look at the ankle joint angle.

I don't know if you're an expert on all this bio-mechanical stuff or just scratching around for a research project. If the latter then go and have a look on slowtwitch for stuff posted by the legend that is (DR) Andrew Coggan.

chrisw12

Ok, I'm a bit bored and this is quite interesting, did a quick search and found this:-
http://forum.slowtwitch.com/cgi-bin/gfo ... =;#3020952

In which his last post he states '...The optimal saddle hiehgt is a range of several centimeters; a few millimeters one way or the other is essentially meaningless...'

Which suggests to me that the good Dr is speculating that saddle height and thus knee angle is not important.

You (op) think it is and think you'll find a correlation?

InPursuit

chrisw12 wrote:

Ok, I'm a bit bored and this is quite interesting, did a quick search and found this:-
http://forum.slowtwitch.com/cgi-bin/gfo ... =;#3020952

In which his last post he states '...The optimal saddle hiehgt is a range of several centimeters; a few millimeters one way or the other is essentially meaningless...'

Which suggests to me that the good Dr is speculating that saddle height and thus knee angle is not important.

You (op) think it is and think you'll find a correlation?

I have a lot of respect for the good doctor and his work with power based training but didn't realize he was also into fitting to the extent of disagreeing with Dr Pruitt! As for his comment re optimum saddle height one has to wonder why he has set his own saddle height to 725 if a few centimeters here and there is unimportant - why not 720 or 730?

My understanding is that ankle joint is a constant for each cyclist so when you change saddle height its the knee angle that will be changed to compensate and not the ankle. However ankle joint angle comes into play when fitting someone in a stationary position as most tend to drop their heel when stationary (when they stop pedalling) which would change their knee angle and render the process inaccurate. This is why a dynamic fit (using pictures while cyclist is pedalling and protractor software to measure) is usually preferred.

Alex_Simmons/RST

You can change saddle height down and not lose power but going a bit too high isn't good. The other main factor is aerodynamics, which is crucial for TT/pursuit performance.

You are seeking to increase power to CdA ratio since that is the primary determinant of how fast you will ride. Playing with saddle height can have quite substantial impacts on aerodynamics.

When I change bike set up from mass start track racing set up to pursuit set up, I find I need to make a slight change to saddle height (only a mm or 2), mainly due to different position on bike and where on saddle I end up spending most of my time.

Power/performance wise prob not a lot in it, but I "feel" better on the bike when I make the change. I have no ankle on one side any more and so any change in extension length must be taken up by the knee flexion. On the track bike, even before my amputation, I could always feel if saddle height was out a fraction.

Anyone making sizable set up changes leading up to a major goal event is playing with fire. That sort of stuff should be sorted out well ahead of time.