What Mechanism Stimulates Breathing During Exercise?

If you have ever spent any time exercising, you know that breathing rates generally increase with greater exertion. The metabolic processes that govern human respiration are complex, depending on and responding to multiple physiological and environmental factors. The human body is exceptionally fine-tuned to handle multiple states of activity and metabolic needs. The mechanisms that control breathing during periods of exercise include regulatory systems that differ somewhat from those that control breathing during periods of normal activity or rest.

  1. Breathing

    • Human respiration is primarily an involuntary process. Although you can consciously modulate your breathing, it is generally managed by the autonomic nervous system. Your brain controls this process. The drive to breathe is not caused by lack of oxygen. Instead, the build-up of carbon dioxide in your blood, the body's primary metabolic waste product, causes your brain to induce respiration. The diaphragm is primarily responsible for controlling the muscular aspects of inspiration and exhalation. When it contracts, it pulls the lung spaces open, creating a negative pressure that allows oxygenated air to infiltrate lung tissues. Air laden with carbon dioxide is pushed out when the diaphragm relaxes. This process is called gas exchange.

    The Circulatory System

    • The human respiratory system is closely and inextricably linked to the cardiovascular system that pumps blood throughout your tissues, delivering oxygen for metabolism and carrying carbon dioxide to the lungs for clearance. Chemical receptors in circulatory and muscle tissues play a significant role in governing respiration, especially during periods of exercise. Increased production of carbon dioxide and other waste products during periods of high activity stimulates these receptors. They send relay signals to the brain, across nervous system pathways, triggering your brain to increase respiration to remove excess carbon dioxide.

    Maintaining Blood pH

    • The normal processes of respiration and circulation continue during periods of exercise. However, your body possesses a remarkable capacity to manage respiration and keep blood pH balanced within the narrow range needed for healthy metabolism, even during periods of physiological stress, like exercise. Carbon dioxide and lactic acid excess resulting from exercise tend to drive blood pH down. Compensatory mechanisms buffer these acids in the blood stream using bicarbonate to maintain a steady state within the circulatory system. To rid your body of carbon dioxide, metabolic processes rapidly convert it from the buffered solution to gas form in the lung capillaries, allowing your lungs to exhale it during the increased respiratory rates induced by exercise.

    Limits

    • Like any human metabolic process, respiratory and cardiovascular capacity can be exceeded during periods of stress, like those experienced during periods of vigorous exercise. When these limits are surpassed, your body begins to feel fatigued and signals you to slow down or rest. Listen to your body. Continuing vigorous activity above your body's tolerance levels can lead to serious health impairments.