Training at altitude and the Hbmass test

It is common practice for high-performance athletes to travel to altitude in order to maximise training adaptations.

In the case of swimmers, this manifests as an improvement in aerobic fitness, resulting in the ability to swim faster for longer and the capacity to recover quicker between intensive bouts of training.  

However, there are a lot of factors that should be considered beforehand as they may impact on the success of an altitude camp.

  • How long should the camp last?
  • What are the ideal location and altitude?
  • What stage of the season is it?
  • How will the camp affect training?

Based on the majority of studies, altitude camps typically range from 7 to 30 days at an altitude between 2000m and 3500m above sea level; however, individuals respond very differently to the exposure.

Hbmass testing enables us to accurately measure the haematological changes that have occurred as a result of being at altitude and help us identify how long these changes are maintained on return to sea level.

A positive adaptation to altitude exposure causes an increase in haemoglobin (Hb) in the blood, meaning more oxygen can be transported to the working muscles, which results in an increase in aerobic capacity.

In the sportscotland institute of sport high-performance lab in Stirling, we determine Hbmass using the carbon monoxide (CO) rebreathing method1, whereby the athlete inhales a small amount of CO and measurements are taken from the lungs and blood to determine how much CO is left in the body. The volume of CO inhaled is not harmful to the athlete and has minimal effect on physical performance or well-being.

Each athlete’s Hbmass results, as well as other performance measures, are critical for coaching and support staff to evaluate individual responses to altitude exposure. This provides essential information in the planning of subsequent camps for optimal duration and altitude required to maximise performance improvements.

This test enables us to assess the physiological changes of each athlete. In an environment where winning margins can be very small it is an important part of the jigsaw in ensuring that we help institute-supported athletes to achieve their full potential.


    1. Schmidt & Prommer (2005) The optimised CO-rebreathing method: a new tool to determine total haemoglobin mass routinely Eur J Appl Physiol 95: 486–495  
Date published: 28 June 2023
Date updated: 28 June 2023


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