Background Paragraph: Sometimes muscles and tendons get injured when a person starts doing an activity before they have warmed up properly. A warm up is a slow increase in the intensity of a physical activity that prepares muscles for an activity. Warming up increases the blood flow to the muscles and increases the heart rate. Warmed-up muscles and tendons are less likely to get injured. For example, before running or playing soccer, a person might jog slowly to warm muscles and increase their heart rate. Even elite athletes need to warm up ( Figure below ). 
Story: Tom and Jim go running together once a week. This week Jim skipped his warm up before exercising, because he was a bit late. Tom warmed up properly before running.
Which runner did a slow increase in the intensity of a physical activity? Which runner didn't do a slow increase in the intensity of a physical activity? Which runner didn't have an increased blood flow to the muscles? Which runner didn't have an increased heart rate? Which runner had an increased blood flow to the muscles? Which runner had an increased heart rate? Which runner has a greater chance of getting a tendon injury? Which runner has a higher chance of getting a muscle injury? Which runner has a lower chance of getting a muscle injury? Which runner has a lower chance of getting a tendon injury?