Introduction
Physical therapy continues to expand horizons, and space physical therapy is one such example. When exposed to microgravity, astronauts experience physiological changes similar to athletes who stop training or elderly patients who are bedridden. Physical therapists work with exercise scientists to prepare and Acclimatize astronauts for spaceflight and repair astronauts after their return. The role of physical therapy begins with helping to reduce pre-flight stress, counteracting in-flight symptoms, and devising a well-planned exercise regime during a stay on the space station. [1]
Adaptions of Human Body to Microgravity
The physiological adaptations of the human body depend on the duration of the flight. Spaceflights can be short spaceflights ranging from one day to 14 days, and long spaceflights of up to 14 days. Physiological adaptation occurs due to two main factors:
- reduced hydrostatic gradient
- reduced ground reaction force.
These factors lead to unloading and abandonment of load-bearing structures [2].
Cardiovascular System Adaptations
As the hydrostatic pressure gradient decreases, blood and fluid in the thoracic head region move upward, and fluid shifts from the extracellular space to the intracellular space, resulting in facial puffiness. The total amount of work done by the heart is reduced. When astronauts are continuously exposed Under microgravity conditions, the volume of the left ventricle decreases. There is some evidence that prolonged exposure to microgravity can cause cardiac atrophy on magnetic resonance imaging. It has been found that upon return to Earth there is a decrease in upright tension, which causes postural Hypotension upon return to Earth [3].
Pulmonary System Adaptations
During the first 3 days in microgravity, CO diffusing capacity increased in standing and sitting positions and returned to baseline, the pre-flight level, after 3 days. Exposure to microgravity results in reduced maximal exercise capacity [4][5].
Adaptations in body fluids
Plasma and red blood cell quality decline during both short and long-duration spaceflight. Hemoglobin levels increase during short space flights and decrease during long space flights due to increased potassium intake. Can go from gaining 0.1 kg to losing 5.9 kg [4]
Loss of body fluid accounts for 50% of weight loss, the rest is fat and protein. Insufficient energy intake leads to fat loss [4].
Neurological Adaptations
Neurovestibular effects, which include immediate reflex motor responses, are very commonly experienced by approximately 70% of astronauts, and astronauts experience postural illusions, spinning, dizziness, vertigo, space motion sickness, including pallor, cold sweats, nausea, and vomiting . this Symptoms of motion sickness can also occur during a flight but subside after 2-7 days. However, although these symptoms can endanger the overall health of astronauts, there is currently no countermeasure.
Among other things, post-flight neurologic symptoms include dizziness when standing and walking, difficulty walking in a straight line, nausea, vomiting, difficulty concentrating, and postural balance. These changes are long and short flights [5][6].
Musculoskeletal Adaptations
In Earth’s gravitational field, the gravitational line passes through the ventral side of the L3 vertebrae, but when exposed to microgravity, the astronaut adopts a more flexed posture and the center of mass moves posteriorly, resulting in more flexor muscle recruitment and extension. muscle loss muscle. Exposure to microgravity results in a shift from type 1 (tonic) to type 2 (phasic). Gravitoreceptors, which carry neural representations of the sense of gravitational direction relative to the direction of gravity, lose their function in microgravity, leaving astronauts less aware Therefore, their posture must rely more on visual and dynamic sensory feedback.
Exposure to microgravity can cause the discs to overabsorb water (hyperhydration), which can lead to back pain, but this is short-lived.
Prolonged exposure to microgravity can lead to muscle atrophy, ultimately leading to decreased muscle strength and function. Bone demineralization [7].
Physiotherapy in space
Training differs depending on whether the astronaut is in the pre-flight phase or the post-flight phase [8][9]
[10]
Pre Flight Stage
Goals of pre flight training
- Astronauts prepare and familiarize themselves with flight conditions
- Treat any pre-existing musculoskeletal and neurological disorders
- Conduct pre flight measures
The pre-flight evaluation includes checking for any pre-existing postural motor control functional movements and joint examination. Ultrasound imaging of previous tasks can be used to study the voluntary contraction capacity of the abdominal and paraspinal muscles.
During the pre-flight period, the exercise program focuses on keeping the astronauts’ cardiovascular function in top condition. The aerobic exercise program begins with aquatic exercises with walking in a horizontal position using a treadmill bicycle ergometer.
The Advance resistance exercise device (AERD) is an intensive exercise that can be performed on the International Space Station, focusing on resistance training for postural pelvic tilt and spine.
Aerobic conditioning and acclimatization should occur during the preflight phase. Ground microgravity stimulation can be accomplished through 5 basic strategies.
- The head is tilted 3 to 12 degrees downward.
- Astronauts spend about 24 hours lying on their backs in the tank and perform complex eye-hand coordination tasks that mimic the skills required for spaceflight.
- Immobilization and bed restraint similar to bedridden patients
- Short parabolic flight with brief weightlessness
In Flight Stage
Effective on-board workouts include treadmill, bicycle ergometer, leg rowing ergometer, upper and lower body dynamic resistance training that has been shown to be effective in maintaining joint range of motion and muscle strength.
The AERD stimulates free weight exercises using a piston-driven vacuum cylinder and flywheel system to work all major muscle groups. These exercises include squats, deadlifts, calf raises, and more.
In addition to this space loop can be used.
Post Flight Reconditioning
The postflight reconditioning is applied within 24 hours of return.
The major goals here are:
- Prevention of any short-term or long-term painful condition such as low back pain
- Addressing any mission-related physical health issues
- Return to pre flight physical fitness level
Principles of reconditioning include:
- Regain postural control muscle control and balance
- Normalization of muscle recruitment by mechanisms of motor control
- Train the postural control relative to the line of gravity
- Once the posture is corrected, use strength training
The reconditioning protocol is as follows :
Return + 1-2 days
The initial examination includes an examination of the musculoskeletal system. Begin with isolated voluntary contraction of large anti-gravity muscles such as the paraspinal abdominal and vastus medialis. The program should always start with training trunk control ultrasound imaging can be used here to look for muscle movement and contraction. While training for the upper limbs it is important to look for any compensation and subtle movement.
While retraining posture it is important to train movement in the entire plane as in micro gravity sagittal plane movement predominates.
Training begins with eyes open and should continue into eyes open as the astronaut relies heavily on vision in microgravity. To restore movement patterns and proprioception motor control strategies.
Return + 3-4 days (R+3-R+4)
Improvements can be made in motor control and postural exercises. TheraBands can be used for strength training. Functional training such as sit-to-stand activities can be used. Endurance training can be done by holding a specific position.
Return + 4-5 (R+4-R+5)
From here workouts are monitored along with a sports scientist. Water exercises are very helpful in this phase. Follow-up, how to improve movement on a standard treadmill and bicycle ergometer. Balance and coordination are tested during this phase and motor control strategies can be developed developed from here.
References
- ↑ Das S. Physiotherapy for Astronauts in Zero/micro Gravitational Environments. Available from https://www.practo.com/healthfeed/physiotherapy-for-astronauts-in-zero-micro-gravitational-environments-39184/post [Last accessed 4 December 2021]
- ↑ Sneha, K. R., Hiral, M. S., Chhaya, V. V., Jaimala, S., Swati, S., & Amita, M. (2013). Exercise Training for Astronauts-A Review. Indian Journal of Physiotherapy and Occupational Therapy, 7(4), 62.
- ↑ Convertino V.A. et al. Changes in the size and compliance of the calf after 30days of stimulated microgravity. Journal of Applied physiology 1989,66,1509-1512.
- ↑ Jump up to:4.0 4.1 4.2 Jack H Willmore. Physiology of sport and exercise. 3rd edition.chap 11 exercise in hypobaric, hyberbaric and microgravity environment. Pg 360- 374. Editor: lori Garrett.
- ↑ Jump up to:5.0 5.1 Mc kardel.chapter: microgravity: Last frontier.pg 665-719
- ↑ Bacal K, Billica R, Bishop S: Neurovestibular symptoms following space flight. J Vestib Res 2003;3:93–102
- ↑ Lambrecht G, Petersen N, Weerts G, Pruett C, Evetts S, Stokes M, Hides J. The role of physiotherapy in the European Space Agency strategy for preparation and reconditioning of astronauts before and after long duration space flight. Musculoskeletal Science and Practice. 2017 Jan 1;27:S15-22.
- ↑ Kale, Sneha & Master, Hiral & Verma, Chhaya & Shetye, Jaimala & Surkar, Swati & Mehta, Amita. (2013). Exercise Training for Astronauts – A Review. Indian Journal of Physiotherapy and Occupational Therapy – An International Journal. 7. 62. 10.5958/j.0973-5674.7.4.123.
- ↑ Lambrecht G, Petersen N, Weerts G, Pruett C, Evetts S, Stokes M, Hides J. The role of physiotherapy in the European Space Agency strategy for preparation and reconditioning of astronauts before and after long duration space flight. Musculoskeletal Science and Practice. 2017 Jan 1;27:S15-22.
- ↑ . National Space Centre. Astronaut Training Exercises with ClaireAvailable from:https://www.youtube.com/watch?v=XLuIDYuv1UY [last accessed 4/12/2021]