…to make the descent trajectory less steep, thus increasing the distance of the atmosphere flight and reducing acceleration stresses ( or loads ).
Reentry was noticeable by the gradual increase in deceleration stresses ( or loads ) and flames in the windows.
The controlled reentry glide-path makes it possible to reduce the stress-loads in the course of reentry down to 3-4 units.
Such space-flight factors, as ionizing radiation, long-time absence of normal hygienic conditions, increased g-forces …