This is a great, fun activity you can use to introduce cellular respiration to middle school students. For this lab, students will read some background information and answer three pre-lab questions about the cellular respiration equation (elements vs. molecules vs. compounds). Students will take their resting pulse and record it in the data table. Then I have my students run around for a few minutes. I like to take them outside and have them do this if it is nice out, or they can always run down the hall and back or do jumping jacks in class. Then students take their pulse immediately after exercise and again after five minutes of rest. Finally there a few questions to answer when they are finished.