Rising time is defined mathematically for the performance of a system for a unit step response. My research is in the human muscle control. In several trails, I measured the 90% rising time of the muscle reaction between two arbitrarily chosen points. Therefore, the rising time I obtained in each trail depends on the distance of start and target points which are different trail to trail. So, how can I compare the rising times of these trails? Is there any definition of Rising time that is decoupled from the distance between the start and target points? Something like non-dimensional rising-time?