Seems like these should be radio buttons not check boxes. Am I correct that you would only select one posture?
The additional data in your report should be set up as a table with one record for each posture. You can then link the record where you make the assessment to this added table by the posture value--which can be either the text shown or an ID field defined in this new table.
There are then a number number of ways to show this additional data after selecting a posture value.