Cardiorespiratory exercises come in a variety of forms. They can range from long-distance running and cycling to short-duration, high-intensity activities like 400-meter sprints and kettlebell swings. Everything has sets of pros and cons, and cardiorespiratory training is no exception. Too much or too little cardiorespiratory training can have negative side effects that can lead to the deterioration of your health. The key to better health is to find a balance between training and resting.
With a higher demand for oxygen during cardiorespiratory exercise, free radicals are produced by your body in larger quantities as a byproduct of cellular respiration -- the process of making energy in your cells. Free radicals are unstable compounds that break down cell membranes, DNA and protein structures. To counteract the damaging process, your body's antioxidants, which are commonly in the form of vitamins A, C and E, sacrifice themselves to make the free radical stable to avoid further cellular damage. However, free radicals are only harmful if you do too much exhaustive cardio, says exercise physiologist Len Kravitz of the University of New Mexico. With an adequate amount of antioxidants in your diet and regular exercise, the amount of cellular damage is minimal.
Wear and Tear
Since most cardiorespiratory exercises involve the lower extremities, excessive exercise without adequate recovery can cause your joints to wear and tear like a set of brakes on a bike. Repetitive trauma, such as tendinitis and stress fractures, are usually caused by poor technique or overtraining, according to the Mayo Clinic. For example, patellofemoral pain syndrome, also known as runner's knee, is the most common injury among most runners. This ailment is associated with pain underneath the kneecap, according to registered massage therapist and science author Paul Ingraham of "Save Yourself." Preventing excessive wear and tear, start gradually and progressively increase the distance or duration of the exercise.
With proper care, cardiorespiratory training's pros outweigh the cons. Not only does your heart get stronger, your ability to sustain moderate- to high-intensity exercise increases as your body resists fatigue and muscle cramps. This is called your lactate threshold, the tipping point at which the rate of lactate accumulation exceeds the rate of lactate removal from your muscles. Lactate is a source of short-term fuel produced by glucose metabolism, which is shuttled to your liver to be recycled into glucose. When your lactate threshold is reached, fatigue and muscle cramps begin to settle in. In a study published in "Journal of Applied Physiology," trained subjects had a 34-percent higher lactate removal rate than untrained subjects after each group performed bouts of high-intensity exercise for 60 minutes.
You don't have to spend an hour trudging on a treadmill or pedaling on a stationary bike to burn a high number of calories. High-intensity exercise over a shorter period of time can fire up your metabolism for many hours after exercise. This is due to what is called EPOC -- excess post-exercise oxygen consumption -- in which your body uses fat and glucose as sources of fuel to repair muscle and bone damage, balance hormones, cool down your body and deliver nutrients to your cells. According to Kravitz, EPOC can elevate your metabolism for anywhere from 15 minutes to 48 hours after exercise, depending on the training intensity, quality and duration. In a 2011 study published in Medicine and Science in Sports and Exercise, 10 men who performed 45 minutes of vigorous cycling sustained an elevated metabolism for 14 hours.