Can You Do Too Much Cardio?

Are you spending hours running on a treadmill or working out on an elliptical machine to lose weight? Sure, cardiovascular exercise burns fat and gives your heart a workout, but doing too much cardio has its drawbacks, and there are some good reasons to not become a slave to your cardio routine. Too cardio can actually work against you if you're trying to become lean and healthy.

Cardiovascular Exercise Puts the Body under Stress:

When you do a cardiovascular workout, you put your body under stress. This type of stress is a good thing in the sense that it forces your body to adapt, so you develop better endurance and the ability to deal with future stress. But cardiovascular exercise of moderate-intensity also stimulates the release of cortisol, the so-called stress hormone. If you do cardiovascular exercise of at least moderate-intensity for an hour or more, this increase in cortisol can become substantial.

What's so bad about cortisol? Cortisol has a variety of undesirable effects on the body. It decreases the body's sensitivity to insulin, and it contributes to bone breakdown. It also suppresses the immune system. Colds and respiratory infections are more common in marathon runners the week after they complete a race, which is due to the rise in cortisol level from doing too much cardiovascular exercise.

The rise in cortisol that comes from too much cardio is enhanced when you're not getting adequate nutrition, especially carbohydrates. During cardiovascular exercise with inadequate nutrition, your body senses low glycogen stores and releases more cortisol. Thus, the combination of long-duration cardiovascular exercise and calorie restriction is especially detrimental.

Too Much Cardio Breaks Down Muscle:

Moderate amounts of cardio helps to speed up fat loss and can help you get slimmer more quickly, but don't overdo it. If you do, you'll not only break down fat but lean body mass as well. This is the effect of cortisol at work. When the body senses low glycogen stores, cortisol is released, and the body starts breaking down muscle to use as a fuel source.

This loss of muscle tissue not only reduces strength, it slows down your metabolism and makes it more difficult to lose fat as your muscle mass declines and your body senses a chronic low-fuel state. One way to avoid this is to do moderate amounts of cardio, keeping your sessions to 45 minutes or less and including a day of rest in between. You can also doing short periods of high-intensity cardiovascular exercise (20 minutes or less) in the form of high-intensity interval training. Shorter cardio sessions reduce the amount of cortisol release.

The other way to reduce the negative effects of too much cardio is to make sure you're eating enough calories and carbs to keep your body well-fueled during cardiovascular exercise. If you're doing an hour or more of cardiovascular exercise a day and restricting calories at the same time, fat loss will slow over time as your body slows down the rate it breaks down fat to conserve energy.

Too Much Cardiovascular Exercise Can Lead to Overtraining and Injuries:

Too much cardio increases the risk of injury, especially if you're not cross-training and giving yourself a day of rest between long cardio sessions. You also run the risk of overtraining, which decreases performance and causes you to psychologically lose your will to exercise. This is your body's way of telling you you're overdoing it, and you need more rest and recovery time. If you're having trouble getting the motivation up to exercise, it may because you're overtraining.

The Bottom Line?

Cardiovascular exercise has benefits both for your heart and for fat loss, but too much of a good thing isn't better. Keep your cardio sessions to 45 minutes or less, and don't do it every day. On alternate days, focus on muscle conditioning. Another alternative to doing straight cardiovascular exercise is to do high-intensity interval training or circuit training on some days to give your body a different challenge. Lastly, make sure you're eating an appropriate number of calories to fuel your workouts.