Hi. I am new to Arduino, so pardon my naivety. I am working on a project that will detect ankle movement using some sort of ankle brace. Specifically, I want to detect the motion of extending the foot forward and backward, like kicking a base drum pedal, but slower. Here are my questions:
Is there something that I can purchase that is already available? Or do I need to build it myself? Has this been done before?
What type of sensors are recommended? Flex, stretch, both, other?
I think the easiest approach to your problem is to use an accelerometer. You will be detecting the acceleration due to gravity and as the foot changes its angle, the gravity vector will change relative to the accelerometer and you will see it vary its output.
There are accelerometer breakout boards that you can attach to an Arduino so you could probably prototype this quickly without any additional hardware or assembly.
The Arduino Drum Machine: 14-track MIDI drum machine sequencer / groove-box
More general information on your goals might yield useful replies... WHY do you want to measure ankle flexion?
Goniometers are typically used for that sort of measurement, in biomechanics.