Responses of the Cardiovascular Systems to Leg Exercises in Microgravity-like Conditions
Condition: Cardiovascular Deconditioning
Study type: Interventional

Summary: 
      One of the major issues in space explorations is the negative effect of prolonged exposure to
      very low gravity (i.e. a condition often referred to as microgravity or weightlessness) on
      astronauts' health. In this unusual condition the human body undergoes an adaptation process,
      often referred to as "deconditioning", that leads to significant loss of bone and muscle
      mass, hormonal changes, as well as modifications of important cardiovascular parameters.
      While the new physiological state is adequate to the microgravity environment, it results
      unsuitable upon return on earth. Hence after the mission astronauts experience various
      health-related problems and must undertake an intense rehabilitation program. Cardiovascular
      deconditioning originates mainly from a shift of blood from the lower extremities to the
      upper part of the body caused by the absence of gravity. In the long term (i.e. days) this
      causes a loss of blood and body fluid. In the short term (i.e. minutes) it elicits
      modifications to arterial blood pressure and heart rate.

      In this study, funded by the European Union through the project STAMAS, we intend to evaluate
      whether leg physical exercises can lead to a displacement of blood towards the lower
      extremities, therefore ameliorating the upward fluid shift caused by weightlessness. More
      generally, we aim to investigate the short-term response of the cardiovascular system to leg
      exercises in microgravity-like conditions. After a clear understanding of these phenomena we
      will develop a controller that, by monitoring the physiological stare of a subject, will
      compute the appropriate exercise regime to stabilize his/her cardiovascular parameters to
      desired safe values. Our contribution will provide a better understanding of the
      cardiovascular system, and will delineate the physiological ground for the development of
      novel countermeasure devices against the cardiovascular deconditioning during space flight
      based on continuous leg exercises.

      The protocol we propose in this document presents minimal risks for our potential subjects,
      while has the potential to produce important contributions. The cardiovascular parameters we
      intend to analyse are: blood pressure, heart rate and leg blood volume. These signals will be
      acquired non-invasively and with minimal risks. Leg exercises will be performed by means of a
      stepping device (MARCOS) previously developed in our Lab. MARCOS enables to vary the
      resistance applied against knee-extension movements, and therefore it allows a systematic
      evaluation of different exercise intensities. Finally, microgravity conditions can be easily
      emulated by letting the subjects lay on a tilted platform with head-down (i.e. head-down bed
      rest - HDBR, or head-down tilt - HDT) during the exercise sessions, thus inducing a shift of
      body fluid toward the thorax. The most effective inclination angle has proved to be as low as
      -6°, thus constituting only minimal risks for the subjects. In practice, subjects will
      comfortably lay on the negatively tilted platform and will perform stepping at different
      intensities while their cardiovascular parameters are being monitored and recorded in
      encrypted form for subsequent analysis.
    


Intervention name(s): Leg exercises
Intervention type(s): Behavioral
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science