Based upon this week's labs why is it hard for a fit person to get an exercise benefit?

People who are in shape would have a hard time to get an exercise benefit because they are always active. It would take longer for them to become out of breath and therefore it would take longer for them to get there heart beat going faster. A fit person would need to run for a long period of time otherwise there would be no benefit due to the lack of an increased heart rate. The point of the lab was to experince this ourselfs and test our hypothesis. For some people who are in shape it took them 15 to 20 mintues to get their heart rate to increase in speed.