Reliability of video analysis of cycling

[ekristianslund43]

Dear biomechanists,

A colleague of mine uses Dartfish for assessment of cycling kinematics during bikefitting. He uses several measures, the most important being hip and knee flexion.

Can anyone of you point to studies or data on the validity and reliability of Dartfish for assessing joint angles? Are there studies on cycling kinematics using 2D video analysis?

I found this on Dartfish:
Norris BS, Olson SL.: Concurrent validity and reliability of two-dimensional video analysis of hip and knee joint motion during mechanical lifting. Physiother Theory Pract. 2011 May 15. [Epub ahead of print

In your opinion, how much is it possible to improve the reliability and validity by upgrading to higher definition or high-speed recordings?

Thanks in advance,
Eirik Kristianslund
MD/PhD student

[sikander]

If you use high definition system like SRM system (Schoberer Rad Messtechnic; Germany) , you will get improved information about relative contribution of each of the lower limb joints to overall maximal power output . This information can be used to make wide comparison between different cyclists or different bicycle setups, and also as a longitudinal measure to monitor the effect of different training interventions. You will get improved reliablity and validity by upgrading .
____________________
biomedical engineer (http://abiomedicalengineer.com/)

[rbini79]

Dear biomechanists,

A colleague of mine uses Dartfish for assessment of cycling kinematics during bikefitting. He uses several measures, the most important being hip and knee flexion.

Can anyone of you point to studies or data on the validity and reliability of Dartfish for assessing joint angles? Are there studies on cycling kinematics using 2D video analysis?

I found this on Dartfish:
Norris BS, Olson SL.: Concurrent validity and reliability of two-dimensional video analysis of hip and knee joint motion during mechanical lifting. Physiother Theory Pract. 2011 May 15. [Epub ahead of print

In your opinion, how much is it possible to improve the reliability and validity by upgrading to higher definition or high-speed recordings?

Thanks in advance,
Eirik Kristianslund
MD/PhD student

Dear Eirik,

I have been using video analysis of cycling in my PhD and it seems that there are three issues we still do not have enough evidence on:
1- Between-days repetibility of joint kinematics
2- Within-day repetibility of joint kinematics
3- Acuracy on joint angles
For the first issue, most studies using 2D analysis assumed trivial differences between days, but no evidence to day what is the technocal and biological error to measuere kinematics in separate days in cycling (i.e. errors in position of reflective markers, motion variability). For the second issue, most studies use steady-state trials looking at a few revolution that would represent the overall cycling motion. On the third issue, I would suggest looking at the following article:
Umberger, B. R. e P. E. Martin. Testing the planar assumption during ergometer cycling. Journal of Applied Biomechanics, v.17, n.1, p.55-62. 2001.

For improved video analysis, preferebly use high speed cameras with the best possible resolution (see http://iopscience.iop.org/0143-0807/29/4/017/ for more).

In terms of looking at lower limb joint contribution, you need to look at forces on the pedals and not torque on the crank or power output (i.e. SRM measurements).
__________________________
Rodrigo Rico Bini, PhD Student
Sport Performance Research Institute New Zealand
School of Sport and Recreation
AUT University
17 Antares Place, Millennium Institute of Sport and Health
North Shore City, Auckland 0632
New Zealand
Phone: +64 477 2056
http://www.gepecbrasil.com/
http://sites.google.com/site/binirodrigo/