Our heart rate is affected by a variety of things, including our age, medical problems, medicines, food, and exercise level. We're more conscious of our heart rate these days, due to technologies like smartwatches that can measure every beat during rest and exercise. However, there are other factors that can affect our heart rate that we don't think about as much. Our heart rate is influenced by many different systems in our body in order to maintain stability. If one of these systems is not working properly, such as with disease or aging, our heart will need to work harder to keep us stable. The two main systems that regulate our heart rate are the sympathetic and parasympathetic nervous systems. These names explain what they do; the sympathetic system increases heart rate and force of contraction while the parasympathetic system decreases them. Both of these systems are active at all times, but it's how much strength they have that determines how quickly your heart beats and whether it slows down or speeds up. There are several factors outside of our control that can influence how our heart rates. If we are having pain or trouble breathing, this will trigger the body's alarm system and cause us to react by trying to calm down the parts of the body that are causing the problem.