Respuesta :
The answer for this question is D. Use the machine to increase the incline and intensity. The reason for this is the fact that increasing the incline will cause her to work against gravity and the increase in intensity will result in her having to work harder. The difference between this and her running speed increasing is the fact that mentally she can determine what her running speed is, but if the machine is at an incline and the intensity is set higher, she physically has no choice but to push her body, thus resulting in a more effective workout.
Reaching 183 is Tammy's highest heart rate. In order to get most effective workout Tammy should use the machine to maintain or decrease her intensity or she could do additional aerobic exercises immediaely after the treadmill. Doing so, she will change ona activity with another that boosts the effectiveness of the workout.