I believe the answer is the Exhaustion stage because it is the bodies reaction to stress. The body becomes extremely susceptible to sickness because it seems to lose to respond to any new stress. Hope I helped!
Doing a hip-hop dance class at the gym for five minutes three days a week is a good way to increase one`s heart rate; however, if Crystal wants to land in a heart rate zone between 142 to 180 beats per minute, then, she has to dance at a faster pace. Doing something at a faster pace would result in the heart pumping much faster in order to compensate for the needs of the body for that specific moment.
