You have faster heartbeats because your heart has to beat faster to support you on some activity your doing, and your lacking the"professional ability to do it. Olympic athletes have lower because they're trained to do that activity, so their hearts don't need to beat so fast.
<span>One measure is called stroke volume, which is the volume of blood pumped per heart beat. A fit individual has a larger stroke volume, which means a greater volume of oxygen is delivered to the body per heartbeat. This is also the reason fit people have a lower resting heart rate.</span>
