1. A method for analyzing data related to tissue oxygenation, in an apparatus including a processor, comprising the steps of: taking an initial measurement to collect data on a tissue chromophore whose light absorption properties depend on the oxygenation state of the tissue; controlling the operation of a restriction means to restrict blood flow for a first predetermined period in the region where the initial measurement was made while continuing to measure the tissue chromophore; controlling the operation of the restriction means to un-restrict the blood flow after the first predetermined period while continuing to measure the tissue chromophore; and with the processor: using the data collected during the measurements, automatically determining within the data an ischemia start point and an ischemia end point of the first predetermined period; wherein the step of determining within the data an ischemia end point comprises: transforming the data into second derivative points of the tissue chromophore measurement; identifying peaks in the data by identifying second derivative points that exceed an average of local second derivative points by a first predetermined amount; identifying valleys in the data by identifying second derivative points that are less than an average of local second derivative points by a second predetermined amount; identifying peaks that precede valleys within a predetermined time interval to determine a valid peak; and producing a correlation coefficient based on the second derivative points between each valid peak and its related valley versus the actual second derivative data.