[Bone examination by noninvasive methods during prolonged hypokinesia]

Area of Science:

• Bone metabolism and physiology
• Space medicine and physiology
• Non-invasive diagnostic techniques

Background:

• Prolonged bed rest can lead to significant skeletal demineralization.
• Understanding bone loss mechanisms is crucial for long-duration spaceflight and terrestrial rehabilitation.
• Countermeasures are needed to mitigate the adverse effects of unloading on bone health.

Purpose of the Study:

• To investigate the effects of 120-day bed rest on skeletal bone mineral density.
• To evaluate the efficacy of different countermeasures (drugs, exercise, combined) against bed rest-induced bone loss.
• To assess the diagnostic and prognostic value of non-invasive techniques for monitoring bone changes.

Main Methods:

• 15 volunteers underwent 120 days of bed rest.
• Non-invasive methods including gamma-photon absorption, ultrasound, and neutron-activation analysis were employed.
• Subjects were divided into control and three intervention groups (drugs, exercise, combined therapy).

Main Results:

• Overall skeletal calcium loss was below 0.5% per month.
• Leg tubular bones lost 1-2% calcium per month; heel bones lost 3-4% per month in control, exercise, and combination groups.
• The drug group showed better preservation of leg and foot bone mineral content compared to other groups.
• A correlation was observed between leg bone mineral content changes and ultrasound propagation in the tibia.

Conclusions:

• Bed rest leads to significant bone mineral loss, particularly in the heel.
• Medications appear to be the most effective countermeasure among those tested for preserving leg and foot bone density.
• Non-invasive techniques provide valuable insights into bone changes during unloading and can assess countermeasure efficacy.