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Isotonic and Isometric Muscle Contractions01:22

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Sharp Changes in Muscle Tone in Humans Under Simulated Microgravity.

Liubov E Amirova1, Anastasija Plehuna2, Ilya V Rukavishnikov3

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Spaceflight causes muscle tone loss, necessitating standardized assessments. Dry immersion revealed decreased muscle tone in several muscles, with site-specific variations, highlighting the need for a unified protocol.

Keywords:
Dry ImmersionMyotonPROatonymicrogravitymuscle tonespace flight

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Area of Science:

  • Gravitational physiology
  • Neuromuscular system research
  • Space medicine

Background:

  • Spaceflight leads to muscle atrophy and reduced muscle tone.
  • Standardized protocols are crucial for assessing neuromuscular changes in altered gravity.
  • Dry immersion (DI) is a model for simulating microgravity effects.

Purpose of the Study:

  • To develop a unified protocol for assessing muscle tone changes.
  • To determine the immediate effects of support withdrawal on muscle tone.
  • To investigate muscle tone changes during 2-hour Dry Immersion (DI) and their site dependency.

Main Methods:

  • Utilized the MyotonPRO device for objective muscle tone measurements.
  • Assessed muscle tone in trunk, leg, and foot muscles of 12 healthy volunteers.
  • Employed Dry Immersion (DI) to simulate microgravity conditions for 2 hours.

Main Results:

  • Significant decreases in muscle tone observed in tibialis anterior, soleus, erector spinae, and tendo Achillis at the start of DI.
  • Muscle tone reduction intensified over the 2-hour DI period.
  • Gastrocnemius muscle showed increased tone, and muscle tone varied by measurement site.

Conclusions:

  • Muscle tone is significantly affected by simulated microgravity, with varied responses across different muscles and sites.
  • Myotonometry is a sensitive technique for detecting these changes.
  • A standardized protocol is essential for comparing muscle tone data across studies in gravitational physiology.