The heart is a muscle. Like any other muscle, training makes it stronger. Cardio exercise also strengthens the cardiovascular system by stimulating capillary growth to deliver more oxygen to muscle cells, decreasing blood pressure and helping you maintain a healthy weight
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Any exercise that makes the heart beat at about 50 percent of its maximum for an extended time is considered cardio. However, as with nearly everything in life, you can do too much of a good thing.
Read more: Can You Do Cardio Exercise Every Day?
More Isn’t Always Better
Exercise is a physical stressor on your body. The benefits of exercise aren’t caused by the activities that are done, but rather from how the body adapts to an exercise afterward by becoming stronger. This adaptation only occurs when the body is allowed to recuperate. Working out for increasingly lengthy sessions does nothing useful when there isn’t enough recovery time.
According to a study in the June 2012 issue of Mayo Clinic Proceedings00473-9/fulltext), regular exercise is very effective for the prevention and treatment of many chronic diseases and will improve cardiovascular health and longevity. However, too much cardio can cause an unhealthy changes in the heart and large arteries, atherosclerosis or a stiffening of the large-artery wall.
Disturbingly, researchers observed more atherosclerosis in experienced marathon runners and, during follow-ups, the rates of cardiovascular problems in the marathoners were the same as those of people with a history of heart disease.
Another study in the January 2016 issue of Physiological Reviews concluded that long-term endurance training at high levels seems to increase the incidence of atrial fibrillation (AF), which is an irregular, sometimes rapid heartbeat that can cause reduced blood flow. The study concluded that the risk of AF increased with the number of days per week of vigorous physical activity.
Raising the Risk of Injury
Overuse injuries can occur with any repetitive movement, whether it’s typing, swinging a tennis racket, or throwing a ball. Cardio also involves repeating the same motions for an extended time.
For example, a 2012 research article found significant evidence that running more than 40 miles per week can cause:
- Stress fractures in the tibia
- Calf muscle tears
- Artery entrapment
- Achilles tendon injury
Other issues that can be caused by excessive cardio training include back problems, osteoarthritis, hip and knee damage and painful tendonitis.
The best approach to avoid overuse injuries is to mix it up a bit. Instead of focusing on one exercise exclusively, build variety into the program by doing a variety of activities like biking one day, strength-training the next day and doing yoga on the third day. Doing this could help prevent injury by letting the body use different muscle groups and avoid too much stress on any single muscle or joint.
The Importance of Rest
The American College of Sports Medicine says that rest is a crucial component of a healthy workout routine. Dedicating some time to recovery is a smart way to prevent overuse injuries. Try to schedule a rest day at least one or two times per week. Short breaks during a workout are another way to get the most benefit while preventing injuries.