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Intensive exercise training during bed rest attenuates deconditioning

J E Greenleaf¹

¹Laboratory for Human Environmental Physiology, NASA, Ames Research Center, Moffett Field, CA 94035-1000, USA. jgreenleaf@mail.arc.nasa.gov

Medicine and Science in Sports and Exercise

|February 1, 1997

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High-intensity exercise training during bed rest can mitigate physiological deconditioning. Different exercise protocols, such as isotonic cycle ergometer exercise and isokinetic exercise, impact various physiological markers differently.

Area of Science:

Space Physiology
Exercise Physiology
Human Adaptation to Stress

Background:

Prolonged bed rest induces significant physiological deconditioning, mirroring some effects of spaceflight.
Maintaining physical capacity and mitigating adverse health effects are critical for astronauts and patients requiring extended immobility.

Purpose of the Study:

To evaluate the efficacy of two distinct exercise training regimens: high-intensity, short-duration, isotonic cycle ergometer exercise (ITE) and high-intensity intermittent resistive isokinetic exercise (IKE).
To determine the impact of these training regimens on cardiorespiratory fitness (peak VO2), muscle function, body composition, fluid balance, and orthostatic tolerance during 30 days of head-down bed rest.

Main Methods:

A 30-day, 6-degree head-down bed rest study.

Keywords:

NASA Center ARC NASA Discipline Number 18-10 NASA Discipline Regulatory Physiology NASA Program Space Physiology and Countermeasures

Related Experiment Videos

Comparison of no exercise (NOE) control group with ITE and IKE training groups.

Measurement of peak VO2, muscle mass, strength, endurance, proprioception, psychological performance, hypovolemia, water balance, body composition, and orthostatic tolerance.

Main Results:

ITE maintained work capacity (peak VO2), plasma and red cell volumes, and induced positive body water balance, but negatively impacted sleep quality and concentration.
IKE attenuated decreases in peak VO2 by 50% and red cell volume by 40%, induced positive body water balance, and had no adverse effects on sleep or concentration.
Neither ITE nor IKE improved orthostatic tolerance compared to the NOE group.

Conclusions:

Specific components of the deconditioning syndrome can be modulated by the duration and intensity of ITE and IKE training.
Comprehensive training protocols combining different exercise modalities may be necessary to fully counteract the physiological and psychological deconditioning associated with prolonged bed rest.