iPhone accelerometer.

Yeah, the maximum sampling frequency with these apps, is 100Hz. Which is a a little slow for running but should be fine for walking. We'll see what the data starts to look like.

Stew, do you have first hand experience of using tibial mounted accelerometers?

 

Simon

I have done a very small bit first hand, but one of my lecturers was very interested in this and the methodology behind it....the mounting is so essential, as any 'wobbling' caused by soft tissue movement etc is going to ruin the data....at a very high recording frequency some this 'noise' can be filtered out, but even with walking..at 100 Hz the data should really be filtered around 8-12 Hz, and once you start using this acceleration data to calculate velocity and displacement there could be large error creeping in, so filtering is really going to smooth the data out... and with heel strike in walking with some people i think you will still be loosing data...but obviously your data may prove me wrong.

 

I've been looking into the i-phone sampling frequency. It seems the hardware is capable of 400 Hz but Apple limit it to 100 Hz. I've also been looking at sampling rates of other gait analysis systems and noted a number of studies using f-scan, in which walking was analysed using a sampling rate of 50 Hz.

My dummy i-phone arrived today so now I can keep people balanced!

 

Thats why I wouldn't trust studies looking at gait at 50 Hz...in video data, pressure data or any other data. The heel strike transient at initial contact will never be picked up at this rate, and therefore loading rates and impulses which may be just as important as peak pressures will not be accurate.

It would be great if Apple could be talked into 400Hz!!!

 

http://www.ncbi.nlm.nih.gov/pubmed/21097067