In this activity, learners will train to increase bone strength and to improve heart and other muscle endurance by performing jump training with a rope, both while stationary and moving. 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 muscle and bone loss while floating 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.