When you exercise, you undergo several physiological changes, or changes that happen within or to the body. Your body begins to perspire, your heart beats faster and you begin to breathe harder. All of the changes that take place are connected, and knowing how and why they are connected not only gives you a better understanding of the exercise process, it allows you to have a better exercise experience overall.
Heart Rate
Your heart rate, or pulse, is the number of times your heart beats each minute. Depending on age and fitness level, adult pulse rates range from 60 to 100 beats per minute. The heart pumps blood throughout the entire body with each beat, so heart rate is a good indicator of your fitness level, or the strength of your heart. The lower the heart rate, the stronger your heart, as it can pump more blood with each beat.
Breathing Rate
The rate at which you breathe, also referred to as ventilation, is about 12 breaths per minute while at rest. Each time you breathe in (or inspire), oxygen is delivered to the blood, then transported to the working muscles where it is needed for energy metabolism. When you exhale (or expire), you breathe out the waste product carbon dioxide from energy metabolism.
Effect of Exercise
During exercise, both heart rate and breathing rate increase. This increase is fueled by the working muscles' demand for oxygen. The heart begins to beat faster to deliver oxygen more quickly, and you begin to breathe faster to bring in more oxygen to meet that demand.
Recovery
When you stop exercising, your body begins to recover, but you may notice that your heart rate, and even breathing rate, is still elevated three to five hours after you have ceased exercise. This is because your body has entered a state of oxygen debt after exercise, and because there are still metabolic byproducts, such as lactic acid and carbon dioxide, in the body. These byproducts must be cleared before your body can return to its original resting, or homeostatic, level. The heart continues beating faster to maintain this process and to reattain your body's homeostasis levels. How long your heart rate and breathing rate remain elevated depends on the level of exercise intensity.
Adapting
As you adopt a plan of regular exercise, you will start to notice long-term changes taking place. Your resting heart rate will decrease--and while your breathing rate may not change, due to the fact that your lung volume cannot change, your heart will be more efficient at pumping blood and delivering oxygen with each breath you take. Exercise at certain intensities will become easier, and your heart rate will be lower at these respective intensities than before because the heart will become stronger.
References
- "Exercise Physiology: Energy, Nutrition and Human Performance"; William McArdle, Frank Katch, Victor Katch; 2007
- "Medicine and Science in Sports and Exercise"; The Effect of Steady-State Versus Interval Exercise on Excess Post-Exercise Oxygen Consumption"; Brown, E A.; Kim, M S.; Kern, M; May 2003
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