This dissertation aimed to explore the usefulness of using force derivatives for onset detection in the isometric mid-thigh pull test. First, we examined applications of three differential calculus principles, first and second derivative, and curvature using visual detection as a reference under different baseline conditions. Second, we compared the best derivative method to a threshold-based method using visual detection as a reference. Results of our first investigation showed trivial differences between many differential calculus methods and visual detection. However, statistical differences exceeding a trivial effect was observed when instantaneous force and rate of force develop were examined. Through the first investigation, first and second derivative emerged as possible viable methods for baseline with a countermovement and for all other baseline conditions, respectively. Results of the second investigation showed similarities to the first investigation with respect to onset time. However, examination of instantaneous force and rate of force development indicated that a threshold-based method tended to overestimate compared to visual detection and a first and second derivative combined method. In fact, the difference between visual detection and the first and second derivative combined method ranged from trivial to moderate under all baseline conditions while the threshold-based method often reached a large difference. Overestimation by the threshold-method was more pronounced for rate of force development. In conclusion, while not perfect, the first and second derivative 3 combined method appears to hold possible practical potential and may be used as an assistant method for entry-level sport scientist plus using visual detection for obvious erroneous values.