In this activity, learners will train to improve lung, heart, and other muscle endurance as they walk a progressive, measured distance. Learners measure out a course according to specific distances, walk/jog/run the distance, and record and graph their observations. This activity simulates how astronauts must train before missions in order to build up the endurance required to move in space. An embedded video on this page showcases the activity. Learners can complete this activity as part of NASA's Fit Explorer Challenge, in which learners train like astronauts, set goals, track their progress, and accumulate points to progress through Exploration Levels and earn certificates.