As a former cardio queen myself, I cannot speak enough about all of the benefits of aerobic exercise:
- Reduced risk of heart disease
- Improved blood cholesterol and triglyceride levels
- Improved heart function
- Reduced risk of osteoporosis
- Improved muscle mass
(IDEA Health and Fitness Association)
However, most individuals fail to comprehend is how much is too little or too much! People tend fall into those two categories (overwhelmingly the first). None the less, I think it is important to be informed of the dangers of excessive cardiovascular exercise
So what’s too little aerobic activity?
Experts claim that an individual must perform cardiovascular exercise for at least twenty minutes in order to increase heart rate enough to promote fat loss and muscle growth. Studies indicate that interval training inhibits the most muscle growth, while running promotes the most fatloss.
I advise switching up cardio for maximal caloric burn and muscle growth. When your body gets used to the same activities, they no longer become challenging and thus, require less effort. The harder your body has to work, the more calories you burn, and the greater physiological adaption!! (See blog: High Intensity Interval Training)
When does cardiovascular exercise become impair health and weight-loss goals?
Last semester I took an Exercise and Nutrition course where I learned first off the dangers of overtraining–including muscle fatigue, altered hormonal functioning, increased risk for injury, lowered psychological health –“burn-out,” insomnia, irritability, overall decreased performance, and impaired immune function.
If that was not enough to change my cardio habits this was:
Excessive cardio over time causes heart damage and inhibits weight loss goals by slowing the metabolism.
Two years ago, The New York Times published an article discussing a study British scientists conducted comparing hearts of male marathon runners to those of non-endurance athletes. They discovered that half of the lifelong endurance runners (age 50-67) had a condition known as fibrosis. However, the hearts of the non-endurance athletes as well as the younger marathon runners (below age 50) did not. “Fibrosis, if it becomes severe, can lead to stiffening or thickening of portions of the heart, which can contribute to irregular heart function and, eventually, heart failure. (Reynolds, The New York Times)”
Canadian and Spanish scientists have also performed similar studies on rats, mimicking excessive training conditions. After a month trial (equivalent to 10 yrs in humans), the scientists found themselves comparing originally healthy hearts to those with symptoms of fibrosis. However, after eight weeks (~7 years) without running, the animals hearts returned back to normal.
Although most people do not spend nearly as long in their sneakers as marathon runners, studies indicate that doing more than 60 minutes of cardiovascular exercise begins to produce diminishing results (The Mayo Clinic, 2012). All the benefits of aerobic activity are reached within an hour.
Why the slowed metabolism??
Evolution. Just like when we starve ourselves, our bodies react to excessive energy loss by reducing metabolic functioning. We need energy to perform many bodily functions and if we are exerting to much of it, our bodies assume we may not refuel enough. At the same time many individuals over-compensate caloric needs, assuming they burned more calories than they actually did and thus, over-eating. These two factors combined inhibit weight-loss and often cause the opposite, weight-gain.
Stick to 30-60 minutes of aerobic activity 5-6 days a week and don’t forget to weight train!!! Remember your body needs rest in order for your muscles to repair. I still struggle with this. My overachiever personality doesn’t know how to “rest,” but as I have learned along my fitness journey, always always listen to your body.
references: nasm.org, wedmd.com, The Mayo Clinic, The New York Times, Dr. William Lunn SCSU