Normal Pulse Oxygen During Exercise

The brain monitors levels of oxygen and carbon dioxide in the blood to maintain ideal oxygen levels. During exercise the body uses more oxygen to supply the muscles with energy. To meet the need for additional oxygen, the body increases the rate of breathing to bring more oxygen into the lungs and also increases the heart rate to pump oxygenated blood more quickly throughout the body. A pulse oximeter uses red light to measure the oxygen saturation of hemoglobin.

Oxygen and Exercise

Activity using large muscle groups for an extended period of time requires oxygen to produce energy. The body monitors the levels of oxygen and carbon dioxide in the blood. To make up for reduced levels of oxygen, the body adjusts the breathing rate and depth to bring more oxygen into the lungs. When the blood enters the lungs, a gas exchange takes place and the hemoglobin picks up oxygen.

Blood Oxygen Saturation

The blood oxygen level is a measure of oxygen saturation of hemoglobin, the carrier protein in the blood with an affinity for oxygen. According to a review published In the January 1994 issue of "Physical Therapy," hemoglobin in arterial blood leaving the lungs is about 97 percent saturated with oxygen. By comparison, hemoglobin in venous blood before it enters the lungs from the heart is
about 70 percent saturated with oxygen. According to MayoClinic.com, normal pulse oxygen ranges from 95 to 100 percent. Any level below 90 percent is considered low oxygen saturation.

Exercise at High Altitude

The thinner air of higher altitudes results from fewer molecules per volume in the air. According to Dr. Fred Furang, oxygen saturation decreases to 95 percent at an altitude of 5,000 feet, and oxygen saturation decreases to 90 percent at 10,000 feet. A study published in the March 2009 issue of "High Altitude Medicine and Biology" shows an oxygen saturation decrease during exercise of 10.58 percent at 3,500 meters, a decrease of 13.43 percent in oxygen saturation at 4,200 meters and a decrease of 11.24 percent in oxygen saturation at 5,050 meters.

Measuring Pulse Oxygen

The pulse oximeter clips over the finger or the ear to measure the blood's color using red and infrared light. Hemoglobin turns brighter red when it is saturated with oxygen, and when the oxygen level decreases, the hemoglobin is dark red to purple. According to a study published in the February 2002 issue of the "Journal of Exercise Physiology, if the oxygen saturation level decreases 4 percent or more below the resting oxygen saturation level, the result may be caused by movement.