Here is a summon place for pervious released dataset
Tennis stroke_inertial data_forehand_backhand_serve
We used Fitbit Ionic(TM) smartwatch as a wearable sensor to collect inertial motion data. Our smartwatch dataset contains three main tennis strokes of serve, backhand, and forehand. The sampling rate for inertial sensors accelerometer and gyroscope is set to 50Hz. Each subject has repeated every
stroke 4 times. Eight right-handed subjects’ recordings were selected from the dataset. Therefore, the selected dataset contains 96 data sequences.
https://ieee-dataport.org/documents/tennis-strokeinertial-dataforehandbackhandserve