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Related Concept Videos

Weightlessness01:01

Weightlessness

When an object is dropped, it accelerates toward the center of the Earth. If the net external force on the object is its weight, it is said to be in free fall; that is, the only force acting on the object is gravity. Galileo was instrumental in showing that, in the absence of air resistance, all objects fall with the same acceleration g. However, when objects on the Earth fall downward, they are never truly in free fall, because there is always some upward resistance force from the air acting...
Acceleration due to Gravity on Other Planets01:24

Acceleration due to Gravity on Other Planets

The gravitational acceleration of an object near the Earth's surface is called the acceleration due to gravity. It can be measured by conducting simple experiments on Earth. However, such an experiment is impossible to conduct on the surface of other planets.
Astronomical observations are thus used to measure the acceleration due to gravity on other planets. This can be determined by observing the effect of a planet's gravity on objects close to it. The crucial factor that helps in this...
Apparent Weight01:09

Apparent Weight

True weight is the measure of the gravitational force acting on an object. However, if the object accelerates, its measured weight is different from its true weight. Similar observations can be made when the object is submerged in water. An object's weight in water is its apparent weight, which is equal to the difference between its true weight and the buoyant forces.
Consider a person standing on a bathroom scale inside an elevator. If the scale is accurate at rest, its reading equals the...
Principle of Equivalence01:18

Principle of Equivalence

According to Albert Einstein (1897-1955), free-falling and feeling weightless are intrinsically linked. If a person were in free-fall under gravity, for example, diving towards the Earth from an airplane, they would feel completely weightless. Similarly, a person descending in a lift may feel partially weightless. Broadly speaking, it is assumed that an object in a uniform gravitational field and an object undergoing constant acceleration in the absence of gravity are under the same...
Variation in Acceleration due to Gravity near the Earth's Surface01:20

Variation in Acceleration due to Gravity near the Earth's Surface

An object's apparent weight is its weight measured by a spring balance at its location. It is different from its true weight, the force with which the Earth pulls it, because of the Earth's rotation. Mathematically, an object's apparent weight equals its true weight minus the centripetal force that keeps it in a circular motion along with the Earth's surface every 24 hours.
The difference between the true and apparent weights is proportional to the square of the Earth's angular speed. Since the...
Metabolic States of the Body: Fasting and Starvation01:24

Metabolic States of the Body: Fasting and Starvation

During the initial hours of fasting, the body uses up its glycogen stores as an energy source. Once these glycogen reserves are depleted, the body begins breaking down stored triglycerides and structural proteins. During this stage, glycerol becomes a key substrate for gluconeogenesis, while free fatty acids undergo beta-oxidation to provide energy for tissues, such as skeletal muscle. In the fasting state, the body spares protein breakdown as much as possible to conserve muscle and structural...

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Weight loss in humans in space.

Akiko Matsumoto1, Kenneth J Storch, Adrienne Stolfi

  • 1Japan Aerospace Exploration Agency, Tsukuba, Japan. matsumoto.akiko@jaxa.jp

Aviation, Space, and Environmental Medicine
|June 28, 2011
PubMed
Summary
This summary is machine-generated.

Astronauts lose weight during spaceflight, with mission duration being a key factor. Factors like preflight exercise and motion sickness also influence bodyweight changes, highlighting the need for countermeasures.

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Area of Science:

  • Human physiology in extreme environments
  • Space medicine and astronaut health

Background:

  • Bodyweight loss is a documented phenomenon in astronauts since early space missions.
  • Extensive mission data, including from female astronauts, exists from the Shuttle and International Space Station programs.

Purpose of the Study:

  • To investigate the association between bodyweight loss during spaceflight and potential covariate factors.
  • To identify predictors of bodyweight change in astronauts.

Main Methods:

  • Statistical analysis of bodyweight change using data from the NASA Longitudinal Study of Astronaut Health (LSAH).
  • Examination of clinical and mission-related covariates associated with weight change.

Main Results:

  • Spaceflight is associated with an average weight change of -2.1%.
  • Predictors of weight loss include first-time astronaut status, preflight weight/BMI, extensive preflight exercise, and baseline electrolyte levels.
  • Severe space motion sickness correlated with greater weight loss, while extravehicular activities showed a protective effect.
  • Mission duration demonstrated the strongest association with bodyweight change (-2.4% per 100 days).

Conclusions:

  • Space missions lead to cumulative bodyweight loss over time.
  • Increased mission durations predict significant weight loss in astronauts without countermeasures.
  • New predictors for intra-mission bodyweight changes have been identified.