Time Normalisation of vertical ground reaction force

Hi everyone. I have vertical ground reaction force data during running and have trials of different lengths so I'm looking to time normalise to 100%

[Mowaz Mohammed Abdul Karim]

Hello, Is it possible for me to find existing data so that I can plot a graph?

[Jan]

This comment does not concern the original quetion. Please open a new thread for a new problem. Explain there, what kind of data your are searching.

[Mowaz Mohammed Abdul Karim]

Oh sorry

Answer 1

[Jan]

This is a job for interp1:

Signal     = rand(1, 1000);  % Test data
HeelStrike = 72;
ToeOff     = 413;
Contact    = Signal(HeelStrike:ToeOff);
ConatctN   = interp1(1:numel(Contact), Contact, linspace(1, numel(Contact), 101));

Now the ground contact phase is normalized to 101.

If this is a bottleneck in your code, use FEX: ScaleTime:

ContactN = ScaleTime(Signal, HeelStrike, ToeOff, 101);

[Shengxiong Zhou]

Hi Jan, I've determine the stance phase of the vGRF file recorded in 1000Hz,

However, how should I extract the knee joint angle during the stance phase? The kinematic file which is recorded in 250 Hz.

I hope this question make sense to you. Thank you for your time.

[Jan]

@Shengxiong Zhou: Unfortunately the question does not make sense to me. If you have determined the time of start and end point of the stance phase, what is the problem of extracting data from the kinematics? Why do the different timings play any role at all? The frame k of the high frequency data belongs to the frame ceil(k/4) of the low frequency data.

[Sir Squirrel]

@Shengxiong Zhou Here is my two cents. Focus on the timestamps (in seconds) where heel strikes and toe off occur, the sampling frequency doesn't play much of a role here.