Recently did an bike fitting on a local bike shop without dynamic info. just a measurement of my legs, arms, inseam … and got an adviced position from the bike fitting tools.
To check all other aspect, i just buy an myvelofit pro access that allow to have dynamic info about all angles (knee, hip …) from a recorded video.
All angle seems fine except knee angle on « bottom position » , 29 degree for an adviced angle of 35/42 degree. For info i use a triathlon bike not a road one.
I’ve read some article with different suggestion : seems that dylan jonhson suggest during one of his video about an angle near to 25 while lot other sources speak about 35/45 range.
Did someone has real world experience about it and for you what is the optimal knee angle that you suggest ?
Measuring Greater Trochanter to Center of Knee Joint to Lateral Malleolus is generally 37-43 degrees (137-143). For most, 37-39 degrees is too much knee extension and some athletes do very well at 44-45 degrees.
I’ll tell you this about knee angle: The more fits I do, the lower I set seat height. Err on the side of less extension. 150-155 extended, or 25-30 degrees if you prefer, is getting into the danger zone for a lot of riders. The thing is, the bad effects of these just barely too high of seats can take months and years to develop. Also I’ve noticed that as we get crank length to the correct range, there is much less incidence of riders self selecting too much saddle height.
Can you post a video of you riding your bike on a trainer?
this.
here are the problems when measuring knee angle:
it depends on the landmarks you choose. you choose different landmarks, the angles change. used to be, as i recall, retul chose as the fulcrum of the knee angle the lateral condyle, and then changed to just the center of the (lateral) knee (which is what we measure to in the F.I.S.T. system). this change changes the angular range. so, first make sure the range you’re using matches the landmarks of the system that sets that range.
it is extremely hard to accurately measure the knee angle in a static setting. you have to re-create the pedaling action of the rider exactly before you measure, and almost everyone drops their heel, riding with a straighter leg, when asked to place their foot at bottom dead center. it takes a really good practitioner to measure cycling knee angle with a goniometer.
which leads us to a dynamic measuring tool, which would be a motion capture system (like retul) or a video over which you lay an angle, and then the measure of that angle is the knee angle. part of the problem with motion capture systems is how the angle is determined. is it the average knee angle during a 20sec capture? because, with some of these systems, the knee angle keeps growing. what that tells me is that the code for that system is seeking the max knee angle found during that 20sec capture. that’s not accurate.
so. bottom line. take a video of you, riding, on a trainer, in profile, bike level. slap it on youtube, use the share feature, copy that youtube URL that uses the “youtu.be” convention, just paste that URL here, in a post, the video will auto-populate, we’ll tell you whether your saddle is properly set.
i’m interested in checking my knee angle via phone video.
this old thread looked on topic - so maybe this is a good place to post?
my questions are:
are there best practices for where/how to set the phone up? on a level box at about the height of the knee a couple feet away from the trainer?
is there a phone app that accurately calculates these angles for us already? is it free?
i have a kickr bike - so I assume leveling the bike just means setting the incline level at zero. i’ll probably set up outdoor bikes on an old school trainer where I can level the rear and front wheel axles to compare to kickr bike fit.
can one get knee over pedal spindle measurement from video also (move phone to center of pedal axle at 3 o’clock crank position?)?
happy to post video afterwards esp. with an acceptable protocol for recording.
