by Dan Bergland, MS

This spring, Hypo2 has been abuzz with a relatively formidable volume of running and swim teams coming to train at altitude in Flagstaff. One of the most important benefits of living and training at altitude is an increase in production of new red blood cells and hemoglobin, a protein in red blood cells that carries oxygen. This adaption helps to deliver more oxygen to the exercising muscles, leading to increased performance.

The simplest measure of an individual’s red blood cell and hemoglobin (Hb) content is a CBC or Complete Blood Count, which measures hemoglobin concentration and hematocrit. However, these test results can be influenced greatly by hydration status. As an example, consider adding 5 drops of red dye to a half-full bath tub versus adding 5 drops to a full bath tub. The shade of red will be different, but the amount of dye will be the same. As in this example, the value of hemoglobin and hematocrit measures will vary quite a bit depending on the hydration state, independent of the amount of red blood cells or hemoglobin in your body.

To get the most accurate measure of hemoglobin, there is a more sophisticated test called Carbon Monoxide (CO) Rebreathing. CO Rebreathing is a specialized test conducted in only a few research labs in the US (including the US Olympic Training Center’s sport science lab in Colorado Springs). Carbon monoxide binds strongly to hemoglobin and acts as a tracer. The test involves finger prick samples before and after breathing a small amount of carbon monoxide gas from a specialized pipe and bag for 2 minutes. Pre- and post-blood levels of CO are measured with a blood gas analyzer. This information is used to determine the athlete’s hemoglobin mass in grams.

As a general rule, average sized male distance runners will have total hemoglobin mass between 800 and 1000 grams and women between 450 and 650 grams. Of greater importance is the difference in hemoglobin mass from pre- to post-altitude training. For athletes living between 7,000ft-8,000ft (2100m-2440m) for 4 weeks, the average increase is approximately 5%. (Since there can be a lot of individual variation, being outside these ranges is no case for alarm.)

We at Hypo2 have been very excited to be part of USA Track & Field’s Distance Initiative project which is tracking the impact of altitude training through systematic total hemoglobin mass testing (as part of an overall effort to get more US runners on the World Champs and Olympic podium). We have been working closely with USATF to test the hemoglobin mass of the scores of US runners arriving in Flagstaff for altitude camp and before departure so that athletes and coaches can better understand and take into account individual responses to altitude training. Additionally, Hypo2 has expanded this service to all teams and athletes training in northern Arizona.

Athletes coming to Flagstaff can contact Hypo2 to schedule Hb Mass testing. Just send an email to Sport Physiologist Dan Bergland at

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