Q. I hear different recommendations about what kind and how much exercise to do. I thought that cardio was good for you, but I've read lately that some experts say that you should not do cardio. I want to strengthen my heart, but I'm confused. What should I do?
A. Anyone who advises people not to do cardio is no expert. Cardio, or aerobic exercise, has several decades' worth of evidence showing that it is good for health, and in particular, for strengthening your heart and lungs. So, yes, you should do cardio exercise. How much you do, and how hard you do it, depends upon your goals. I've written more about that here:
What is cardio?
Cardio exercise is moving your whole body over a period of time, using the major muscle groups (such as those in your butt and thighs) that will get your heart rate up and raise your body temperature. You huff and puff a little, and you work up a sweat. Walking, running, jumping, cycling, skating, swimming, cardio machines like the elliptical trainer and steppers, dancing, aerobics and similar activities are all true cardio workouts.
But even a routine of continual calisthenics, such as squats, lunges, pushups and burpees can provide a cardio workout if you keep moving to keep your heart rate elevated. Assuming that you are fit enough to start and have no joint injuries or other conditions that preclude you from participating in a particular activity, you can do any of these cardio workouts.
Other forms of cardio
Sports that incorporate walking, running and jumping can also be considered to be cardio. These include tennis, volleyball, soccer, basketball, racquetball, squash, softball, playing tag, kickball and so on. Sports tend to be more erratic and vigorous, and it's easy to get injured or to do too much too soon. So it's a good idea to build up strength and aerobic fitness before jumping into vigorous sports to ensure that you're fit enough to handle the demands of the activity.
Weight training is not officially considered to be cardio because traditional moves, such as biceps curls, focus on specific muscle groups, rather than moving the whole body. And muscles are worked to fatigue, which means that the movement ends in a minute or two, whereas in cardio workouts you don't work any specific muscle groups super-hard and you can keep going for hours. Weight-lifting exercise develops more strength than cardiovascular endurance. But, if performed in certain ways, weight lifting can also produce cardio benefits.
Cardio-style weight workouts include performing a fast-moving circuit of weight moves or using dynamic whole-body movements, such as with kettlebell training, or inserting brief cardio intervals, such as two minutes of jumping jacks in between weight-lifting moves. I've written more about that here.
When you start moving the major muscles in your body, your heart beats faster. This gives your body a dose of exercise stress. As a result, the heart (and other physiological systems) adapt and becomes stronger so that when your body encounters this challenge again, it will be stronger and better able to handle it. This principle of putting stress on the body so that it becomes stronger in some way is how all exercise improves health and fitness.
Why cardio is good for you
Depending upon how hard you work and for how long, you can induce different benefits. Easy cardio improves your health risks, while more challenging cardio improves health risks and improves your stamina and fitness level. Alternating both easy and harder intensities with interval training (moving at a high intensity, then slowing down a bit) has been shown to be an effective way to push your body to a higher fitness level while allowing for recovery periods.
Having a strong cardiovascular system means that you are able to deliver oxygen throughout your body effectively. Many physiological processes are fine-tuned as the result of regular cardio exercise: You become better at burning body fat and the improved circulation (which includes the development of more capillaries to increase your blood flow) can help lower blood pressure.
Each bout of cardio can improve your HDL cholesterol and increase insulin sensitivity which then decreases your risk of diabetes. Regular cardio exercise has also been shown to decrease your risk of heart disease and some types of cancer, and you can even experience a boost in your sex drive.
Recent research shows that cardio may help maintain the length of telomeres, or strands in your DNA that are associated with aging when they shorten. Cardio also appears to boost sirtuins, proteins are associated with an increased lifespan. Cardio also preferentially reduces your unhealthy deep belly fat, even if you don't lose weight from it. There are so many proven benefits of doing cardio, that if you come across anyone advising you not to do it — run! (But if you haven't been doing cardio, you'll probably collapse before you can get away.)
Cardio vs. strength training
Often, no-cardio advocates pit cardio against resistance training and claim that cardio doesn't help you lose weight or body fat, and that it's even unsafe. Often, weight lifting is promoted as the only beneficial type of exercise. The truth is, weight lifting is as necessary as cardio and neither one is "better" than the other; they offer different, but complementary, benefits, and all of us should be including both in our weekly workout regimens, whether we exercise to lose body fat and/or weight or to simply improve our health. I've written more about the benefits of weight lifting here.
If humans were living in non-modern conditions, there's a case to be made that we don't need to hop on cardio machines or hoist dumbbells, but as long as most of us are sitting at desks all day and lifting nothing heavier than a remote control, we need to add back the activity that our bodies are missing by doing "exercise"— and that includes cardio and strength training.
How much is too much?
Of course, you can overdo a good thing and that applies to lifting too-heavy weights or running for too long on a hard surface. There are some concerns that excessive amounts of extreme cardio, such as marathon running or long-distance triathlons, may have negative impacts on some aspects of health. I've written more about extreme cardio here and here. Even still, the jury is still out and more research needs to be done. It might be that certain people can better handle certain types of exercise than others. But, yes, you should definitely include cardio exercise in your weekly plan.
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