loss still occurs in the lumbar spine and femur.
38
–
40
Although exercise may be considered sufficient for short duration spaceflights, pharmacological countermeasures should be considered for longer spaceflights. To date, only alendronate has been assessed with a bed rest study
26
and clinical trial during spaceflight.
25
While demonstrating maintenance of bone density, the method of administration and common side-effects are an issue, with 2 out of 11 astronauts participating in the in-flight study withdrawing due to gastrointestinal side