Hamstring injuries in field hockey are very common. Accurate estimates of muscle tendon unit lengths (MTU) and elongation velocities could give insight into the risk of injury during field hockey specific movements. For accurate measurements the hockey field would be best suited. Inertial measurement technology allows for such measurements; however, a method of applying this technology to hockey must first be developed and applied to athletes. The goal of this study is to develop this method and indicate what field hockey-related activities might be accompanied with a higher risk for hamstring injuries. Three elite female field hockey athletes participated in this study, performing ten field hockey-specific exercises. The results obtained with inertial measurement technology were compared to the results obtained with the commonly used optoelectric motion capture system. This method showed very good (0.850 - 0.950) to excellent (0.960 - 1.000) coefficients of multiple correlation values. Furthermore, absolute peak values for MTU lengths and elongation velocities were obtained. The results showed that the MTU length and elongation velocity were higher during running while dragging the ball on the hockey stick than during running without ball. The MTU length was also higher during various types of hits than during running. Additionally, the MTU length and elongation velocity were higher on the left leg compared to the right leg. Excessive stretch and high elongation velocities could indicate a greater chance of muscle injuries. This study shows that MTU lengths and elongation velocities can be obtained with inertial measurements and could in part, explain the relatively high hamstring injury rate among female field hockey athletes.