These data are from the file
in the ‘gait in aging and disease’ database
which is a large collection
of physiologic signals maintained
as a public service
by NIH's National Center for Research Resources.
The following quote from this Web site describes
how the stride intervals were obtained.
Subjects walked continuously on level ground around an obstacle-free path.
The stride interval was measured using ultra-thin, force sensitive resistors
placed inside the shoe. The analog force signal was sampled at 300 Hz
with a 12 bit A/D converter, using an ambulatory, ankle-worn microcomputer
that also recorded the data. Subsequently, the time between foot-strikes
was automatically computed. The method for determining the stride interval
is a modification of a previously validated method that has been shown
to agree with force-platform measures, a ‘gold’ standard.
Data were collected from the healthy subjects as they walked in a roughly circular path for 15 minutes, and from the subjects with Parkinson's disease as they walked for 6 minutes up and down a long hallway.