In this activity, learners will train to develop upper and lower body strength in their muscles and bones by performing body-weight squats and push-ups. Learners perform the exercises over time (week or month) and record and graph their observations. This activity simulates how astronauts must participate in strength training prior to missions in order to compensate for the weakening of muscles and bones in the reduced gravity environment of 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.