Difference Between SpO2 And Vo2Max


Although both measurements involve oxygen, SpO2 and VO2 max differ. One involves the oxygen saturation in your blood, while the other shows how efficiently your body uses oxygen. Let’s look at the two measurements, how to obtain each, and why you would want to know them. We’ll also examine which fitness trackers and watches you can use to easily obtain approximate measurements of both of these respiratory health statistics.

SpO2 Defined

Oxygen saturation or SpO2 measures the blood’s oxygen-carrying hemoglobin relative to the hemoglobin not carrying oxygen. The human body requires a specific level of oxygen in the blood to function properly.

The Normal Amount of Oxygen in Blood

Typically, a healthy human maintains between 95 and 100 percent SpO2. This measure of oxygen tells us a lot about the individual’s health.

Abnormal Oxygen Levels: Hypoxemia and Hypoxia

When the blood’s level of oxygen falls too low, the individual develops hypoxemia. When this occurs, you’ll see its effect on the skin which develops cyanosis, turning blue in appearance.

Untreated, hypoxemia can further develop into hypoxia, defined as low levels of oxygen in bodily tissues. This progression indicates permanent damage to tissues; it can lead to heart damage and brain damage, even death.

How the Body Maintains Normal SpO2 levels

In normal breathing, the lungs disperse inhaled oxygen which binds to hemoglobin. The hemoglobin circulates through your body. During workout, the body’s need for blood oxygen increases. If you’ve ever observed a football player breathing from an oxygen mask between plays, he did so to raise the level of oxygen in his blood.

Measuring Oxygen Saturation

The medical area of pulse oximetry measures the level of oxygen in the blood using a device called a pulse oximeter. These devices usually slip onto the finger, usually the index finger, or the toe. Others attach to the head or fit onto the foot. The designs vary for the age of the person and their medical condition. An oximeter used in measuring a fetus’ Spo2 during the birthing process differs in design from one used to measure an adult’s oxygen saturation. 

Check out one of our most popular fetal/neonatal SPo2 sensors for Nellcor technology oximeters. Part number S303-01P0.

Some fitness trackers measure SpO2 using a built-in oximeter. This appears in the standard readout of vital signs on devices such as Fitbit and Apple watch.

When you work out, knowing how much oxygen circulates in your blood can help you determine whether you’re hitting the right intensity. If your SpO2 hits 90 percent or lower, you should proceed immediately to the emergency room. Your oxygen saturation levels dropped dangerously low.

VO2 Max Defined

In addition to the importance of oxygen saturation, you also need to know your VO2 to maximize your workout. Your oxygen uptake or maximum volume of oxygen (VO2 max) reveals how much oxygen your body takes in and utilizes during work out.

Unlike SpO2, no device measures this directly. Instead, a doctor or trainer typically calculates it using an accepted formula and other vital signs measurements. This respiratory level shows how effectively you train.

VO2 max reflects your heart’s effectiveness at distributing blood to the muscles of your body. It also shows the efficiency with which your muscles extract oxygen from your blood.

The VO2 Respiratory Measurement

Medical professionals express VO2 max in milliliters of oxygen consumed per minute per kilogram of body weight or mL/kg/min. Your VO2 can go up when you lose body fat, but typically, those who register a higher VO2 do so because of good cardiovascular health.

How do you measure VO2?

To obtain the information needed to provide you with your VO2 max, a doctor would have you perform a cardiopulmonary exercise test in the office. In this test, you would wear a face mask that records oxygen consumption and carbon dioxide production while you perform a light workout, such as a treadmill run, bike ride, or other cardiovascular task. The test also measures your heart rate at various exercise intensities.

Rather than having a single “magic number,” VO2 varies by person. Your age, gender, weight, and regular activity level/exercise frequency influence it. Typically, the higher the VO2 max measurement, the better.

Of course, like most vital signs, today’s fitness trackers can provide a rough measurement or approximate the measure. While not as accurate as having your doctor do it, it still offers a close enough number to help you better plan your exercise routines.

How does the VO2 Max help?

Doctors use the oxygen volume measurement to develop an exercise routine that uses heart training zones to maximize fat burning to help overweight or obese individuals lose weight loss. Some fitness trainers with advanced education use this in the same manner.

Normal VO2 Max Varies

Although many factors influence VO2 max, normal ranges do exist for both men and women. The normal range depends on activity level and age. Let’s consider the average ranges for men aged 18 to 45 years old.

VO2 Max Range                    Daily Activity Level


35-40                                      Sedentary     

42.5-46.4                               Active

≤ 85                                         Very active

The average ranges for VO2 max for women aged 18 to 45 years old prove similar, but slightly lower. Still basing the measurements on activity level, the normal ranges follow.

VO2 Max Daily                          Daily Activity Level


27-30                                          Sedentary

33.0-36.9                                   Active

≤ 77                                             Very active

These ranges don’t provide hard and fast numbers–merely averages to guide you if you measure your VO2 max using a fitness tracker or watch. Also, consider that someone with little body fat and a sedentary lifestyle might be fit in the active range.

Improving Your VO2 Max

While both respiratory measurements offer important insight into your health, you can easily improve your body’s ability to take in and utilize oxygen effectively. Bettering your VO2 max sets you up for longer and more challenging cardio workouts. With a higher maximum oxygen volume, you can perform cardio at higher intensities and for longer periods of time. That’s vital if you want to compete in marathons or other road races.

To improve this, try a combination of low-intensity training (LIT) on odd days and high-intensity training (HIIT) on even days. LIT includes biking, hiking, rowing, and running. HIIT includes aerobic exercise that uses a rotation of a few minutes of increased intensity, then a decreased intensity, and back to an increased intensity.

Using the HIIT and LIT combination with a healthy eating regime should help you decrease your percentage of body fat but preserve your lean muscle mass. Tracking your VO2 max throughout this process offers a medical measurement/indicator of your fitness level.

Which Fitness Trackers Measure SpO2 and VO2max?

Now that you know the difference between oxygen saturation and oxygen volume, you’re probably pretty excited to measure them both regularly. Both measures provide you with important health information that can help you recognize indications of serious problems.

You don’t have to go to the doctor to measure these since many fitness trackers take the measurements. Many devices determine the oxygen saturation and the oxygen volume for you. These include the following:

  •       Apple Series 7 smartwatch
  •       Garmin Fenix 5 Multisport GPS Smartwatch
  •       Amazfit Stratos 3 Sports FirstBeat Smartwatch
  •       Garmin Forerunner 935 - Best Garmin Device With VO2 Max
  •       Garmin Forerunner 45 Running Smartwatch
  •       Fitbit Alta HR
  •       Fitbit Charge 2
  •       Fitbit Blaze
  •       Fitbit Ionic

While most fitness trackers and smartwatches take one of the measurements, you’re less likely to find one that measures VO2 max. Most of the trackers from the past two to four years measure SpO2.

Each tracker uses a different method of measuring both data items. For each fitness tracker or smart watch, you will need to read the owner’s manual and determine the method for that specific device. Some of the trackers only measure SpO2 while you sleep or using a few seconds long test during a resting period. This can be a momentary break during a workout or a true resting rate.

Where Can You Purchase Fitness Trackers Online?

Shopping major retailers or the manufacturer websites themselves provides the best results. You can purchase the above devices at e-tailers like Amazon.com. Walmart and Macy’s carry some items. As ubiquitous as smartwatches and fitness trackers seem, if you live in a rural area, shopping online can afford you a much larger selection.

In Conclusion

While SpO2 and VO2 Max differ, both health statistics can provide you with important information about the amount of oxygen in your blood and the amount of oxygen you intake. This can improve your workouts and health. While the doctor can measure them most effectively, using a fitness tracker or smart watch can provide an approximate measurement accurate enough for exercise.