NASA uses the term “countermeasures” to describe the procedures, medications, devices, and other strategies that help keep astronauts healthy and productive during space travel and return to Earth. The Human Health Countermeasures (HHC) Element is responsible for understanding the normal physiologic effects of spaceflight and developing countermeasures to those with detrimental effects on human health and performance. They provide the biomedical expertise for the development and assessment of medical standards, vehicle and spacesuit requirements and countermeasures that ensure crew health during all phases of flight. Pre-flight countermeasures involve physical fitness and exercise and physiologic adaptation training. In-flight countermeasures include nutritional health, physical fitness, pharmaceuticals and sensory-motor training protocols. Post-flight countermeasures target rehabilitation strategies. Prior to flight testing, candidate countermeasures and technologies are developed and refined using ground-based studies.

The HHC is comprised of five portfolios that address physiological research, countermeasure validation and technology development. The portfolios are known as: Vision and Cardiovascular, Exercise and Performance, Multi-System, Bone, and Technology and Infrastructure.