Fig. 1 Collecting sensor data from Parkinson ’ s disease patients. a Distributions of PIGD scores for study visits. Both distributions favored lower PIGD scores; distribution for Study 1 is skewed less than for Study 2. b Position of an APDM Opal inertial sensor attached to the lumbar region using a stretchable belt. The sensor was placed on the lower back of the subject. Accelerometer, gyroscope, and magnetometer data were collected as subjects walked back and forth for 2 min (as part of the UPDRS Part III test) while wearing this