Justin designed an experiment to find out how running up bleachers affects his heart rate. First he records his resting heart rate and then runs up the bleachers 10 times. Each time he reaches the top, he records his heartrate then rests 20 minutes. Which is involved in Justin's experiment?

Justin runs up the bleachers 10 times and records his heart rate after each run, so he repeats the same procedure multiple times. This is repetition. Replication would involve another person or group independently carrying out the experiment.

AI-written and checked against the verified answer.