Fig. 4.

hMFA solution Use Case 2. In Use Case 2, the hierarchical tree (a) was defined similarly to that in Use Case 1 (Fig. 2a) but with the addition of the post-spaceflight data and a temporal layer (time in space). From the global solution (space time), we retained the first four components based on their percentage of variance accounted for (b). Comp. 1 explained 21.97%, Comp. 2 16.42%, Comp. 3 11.25%, and Comp. 4 9.02% of the total variance. The contribution of each layer into the definition of the components can be extracted (c–d). With the incorporation of the temporal layer, it is possible to determine the changes in the component scores for each subject between pre- and post-spaceflight. These can be calculated at the lumbar segment level (e) and for each individual spinal level (f). Each arrow indicates the change that each subject had in the respective component from pre to post-spaceflight. The magnitude of the change can be calculated and used for further analysis. MF: multifidus, Ps: psoas, ES: erector spinae, QL: quadratus lumborum