Version 2.2 TgForce3D Sensor User Guide P a g e | 15Understanding Peak Positive Acceleration (PPA) ValueThe sensor and the internal algorithm have been designed for measuring the Peak Positive Acceleration(PPA) of the tibia. This value is obtained during the initial foot contact. The Z Axis is used for triggeringthe detection but all axes are used in the calculation.Treadmill & Pavement RunningDepending on the type of treadmill used, there may be an important variation in impact level betweentreadmill and pavement running. In many cases, the treadmill running surface will absorb a significantportion of the impact. The TgForce 3D sensor is initially set for normal pavement running. If therecorded cadence is sometimes incorrect, you should adjust the sensor threshold (g) level (seecalibration section).