During heavy exercise, increased breathing is essential for oxygen intake, which fuels muscle activity. The lungs facilitate the exchange of carbon dioxide (CO2) for oxygen (O2). As physical exertion rises, the body consumes more O2 and produces more CO2. Insufficient breathing leads to CO2 saturation in the blood, signaling the brain to increase breathing rate. Rapid breathing can result in lowered CO2 levels, causing anxiety and potentially leading to hyperventilation. Breathing into a bag can help restore CO2 balance. Additionally, the blood pH buffer system reacts to CO2 levels, which is crucial during intense exercise to prevent acidosis from lactic acid buildup in muscles.