Space Physiotherapy

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Original Editor - Srishti Banerjee

Top Contributors - Srishti Banerjee, Kim Jackson and Rishika Babburu  

Introduction

Physiotherapy continues to expand horizons and physiotherapy in space is one such example. When exposed to microgravity , the astronauts experience physiological changes similar to detraining athletes or senile bedridden patients. A physiotherapist works with a sports scientist and prepares and conditions the astronaut for the space flight and reconditions the astronaut after their return. The role of physiotherapy begins with aiding the pre flight stress relief, counteracting in-flight symptoms , design a well curated exercise regime during the space station stay.

Adaptions of human body to microgravity

The physiological adaptations of the human body depends on the duration of the flight. The space flight can be a short space flight which ranges from one day to 14 days whereas long space flight is up to 14 days. The physiological adaptations occur because of two major factors : 1) reduced hydrostatic gradient 2) reduced ground reaction force. These factors leads to unloading and disuse of weightbearing structures.

Cardiovascular system adaptations

As the hydrostatic gradient reduces , there is an upward shift of the blood and fluids in the thoraco-cephalic region and there is shift of the fluid from the extracellular space to intracellular space leading to puffy face. The total cardiac work reduces. When the astronaut is continuously exposed to microgravity the volume of the left ventricle reduces. There is evidence of cardiac atrophy on magnetic resonance imaging resulting from prolong exposure to microgravity. It has been found that while returning to earth there is reduction in orthostatic tension which results in postural hypotension while returning to the earth.

Pulmonary System adaptations

During the first 3 days in microgravity , the carbon monoxide diffusing capacity increases in standing and sitting which returns to baseline i.e pre flight levels after 3 days. Exposure to microgravity leads to a reduced maximal exercise capacities,.

Adaptations in body fluids

Both during short as well as long space flight plasma and red cell mass decreases. The hemoglobin levels increases in short space flight where is reduces in long space flight because of increased potassium intake. The weight can change from a gain of 0.1kg to loss of 5.9 Kg⁵

Fluid loss accounts for 50 % of weight loss and rest is due to fats and proteins. Inadequate energy intake leads to fat loss.

Neurological adaptations

Neuro - vestibular effects are very commonly experienced by about 70 percent astronauts which includes immediate reflex motor response where the astronauts experience postural illusions, rotation ,dizziness, vertigo , space motion sickness which includes pallor, cold sweating, nausea and vomiting. The symptoms of motion sickness also occur during the flight but subsides after 2-7 days. However even though these symptoms can endanger the overall health of the astronaut , currently there are no counter measures for the same.

In addition to this the post flight neurological symptoms includes vertigo while standing and walking, clumsiness, difficulty in walking on straight line, nausea, vomiting, difficulty in maintaining concentration and difficulty in maintaining postural equilibrium. These changes are common in both long and short flight.

Musculoskeletal adaptations

In the earth's gravitational field the line of gravity passes ventral through L3 vertebrae , however when exposed to microgravity astronauts assumes a more flexed position and the center of mass shifts posteriorly leading to a greater recruitment of the flexor muscles and loss of extensor muscles. Exposure to microgravity leads to shift from type 1 ( tonic) to type 2 (phasic) occurs. Gravitoreceptors which carry sensations for neural representation of direction of gravity with respect to the direction of gravity lose their function in microgravity making the astronaut less aware of their posture , therefore they have to rely more on vision and feedback from dynamic receptors.

Exposure to microgravity leads to excessive absorption of water in the intervertebral disc ( hyperhydration) causing back pain , however this is short lived.

Prolong exposure to microgravity results in muscle atrophy which eventually leads to reduced muscle strength and function. Bones under go demineralization.

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