Force Platform Configuration - Gait Lab

[Nick Ball]

Hello Biomech-L readers

We have 3 AMTI force plates that we are looking to put into an existing 2600mm long by 600mm pit. The dimensions of the Foreplates are 600mm x 400mm. Unfortunatley due to structural issues we cannot change the dimensions of the pit.

We are looking to create a gait laboratory and thus would like to get advice on the best configuration of these plates. The options we have are laterally staggering the plates to try and get 2 foot strikes, or aligning them and thus realistically only getting 1 foot strike but targeting would be less of an issue.

Any advice on the best configuration that works with Gait analysis would be great. I will post replies

[Edmund Cramp]

Re: Force Platform Configuration - Gait Lab

I've put a lot of plates in over the years and the most common configuration is two plates adjacent to each other and, if a third plate is available, then space it about 6-8 inches (150- 200mm) further down the walkway in the direction of progression. Some installations offset one or other of the plates slightly to the side but it doesn't make much difference in my opinion - if I was setting up a lab I'd put them all in a line.

A friend of mine spent a long time analyzing the average gait cycle length of his subject population to try and determine the perfect spacing for his lab but told me later that it did seem to have made any difference to the quality of the data or the number of good foot strikes on the plates per trial. The point (IMHO) is that you're looking to optimize the chance of getting one good, clean, strike per trial - if you get two clean strikes in one trial then you're doing well - getting a clean strike on all three plates in one trial will happen occasionally but it's not that common and always makes me suspect "targeting" on the part of the subject.

I'd be far more concerned about getting good solid mountings for the plates and creating a non-obtrusive walkway that sounds the same no matter where the subject steps, than worrying about the actual position of the plates. Finally - in a 3D gait lab you are going to need to know the physical location of the plates within your 3D space so that you get accurate data - so it's always a good idea to keep the force plate locations straightforward and easy to verify.