Recent bed rest results and countermeasure development at NASA

Area of Science:

• Space Physiology
• Human Adaptation to Microgravity

Background:

• Bedrest studies simulate microgravity effects on the human body.
• Head-down tilt (HDT) is crucial for understanding spaceflight adaptation and developing countermeasures.
• NASA bedrest experiments vary in duration, from hours to 17 weeks.

Purpose of the Study:

• Investigate physiological responses to supine posture and inactivity.
• Examine head-down tilt effects on fluid shifts and intracranial pressure.
• Identify effective countermeasures for maintaining astronaut health during long-duration spaceflight.

Main Methods:

• Acute 6-degree head-down tilt experiments.
• Measurement of capillary blood pressure and perfusion in head tissues.
• Analysis of intracranial pressure changes during tilt.
• Evaluation of lower body negative pressure (LBNP) combined with treadmill exercise.

Main Results:

• HDT increases capillary blood pressure (28 to 34 mm Hg) and perfusion, leading to facial and intracranial edema.
• Intracranial pressure rises significantly (2 to 17 mm Hg) during HDT.
• Headward fluid shifts may contribute to increased bone density with long-term HDT.
• Treadmill exercise with LBNP and compression suits simulates physiological stress comparable to upright exercise.

Conclusions:

• Understanding HDT-induced fluid shifts is vital for astronaut health.
• Current exercise hardware lacks the ability to create a head-to-foot pressure gradient in space.
• Treadmill exercise within an LBNP chamber presents a promising, cost-effective countermeasure for cardiovascular and neuro-musculoskeletal health during spaceflight.