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The role of biomarker testing for triathletes

by Edward C Wang

Gaining a competitive advantage is a common goal for all professional athletes and for many who compete at semi-professional or amateur levels. The ways in which these advantages are achieved are as varied as the sport and the type of athlete who trains for it. For example, in long-distance triathlon competitions such as IRONMAN 70.3 or full-distance IRONAM, athletes go through prolonged periods of training that can be divided into two major stages: base training and adaptation. 

During base training, athletes build their “base” performance level with low-intensity sessions to ensure that the body can continuously function in a prolonged state of exercise. In order to improve fitness such as speed and power, high-intensity interval workouts are sprinkled throughout the training periods to expose the body to high levels of stress. During the adaptation stage, recovery weeks are incorporated to allow the body to absorb the stress induced by training and allow adaptations to occur.

The recovery weeks keep the high intensity but reduce the volume of training. The idea behind this approach is to keep the muscles “awake” to the higher intensity but to also allow them to “rest” through shorter intervals and workout sessions.

Part and parcel to how an athlete trains is the outcome reflected in an athlete’s internal status – that is, the physiological state or desired state that training intends to optimize but is imprecisely monitored. Laboratory diagnostic testing may play a role in optimizing performance by providing insights on biomarker levels. These insights, which have traditionally been used to diagnose illness or disease, may help guide various stages of training, such as the periods of rest and recovery following high-intensity and volume training. Monitoring biomarkers associated with recovery status and repair needs can potentially help address the susceptibility to overtrain, suboptimal training adaptations, and the need to taper training to achieve higher levels of performance. 

Monitoring biomarkers can also help guide athletes who have specific endurance performance goals. As endurance capacity is limited by the body’s capacity to consume, transport, and utilize oxygen to fuel sustained oxidative metabolism during prolonged athletic events, monitoring biomarkers related to red blood cells and nutrients that support red blood cell replenishment may provide insights into an athlete’s internal status relative to endurance goals. In addition, due to the high physiologic demands of high volumes of training required for endurance events, biomarkers of immune health may also help inform progress towards endurance goals.

The potential correlation between biomarkers and the state of training may help guide athletic training regimens, especially those geared toward high volume and intensity activities such as long-distance triathlons (e.g., Ironman 70.3 and Ironman). Large clinical diagnostic laboratories may be in a strategic position to enhance athletic performance by offering biomarker testing to optimize personalized long-distance endurance race training. Quest Diagnostics, one of the largest US clinical diagnostics laboratories, is developing the Sports and Human Performance Diagnostics panel of tests to provide athletes who train and compete at any level new and more detailed information about their specific individual internal status. The panel uses blood-based analysis so that training, nutrition, recovery, and preparation strategies can be collaborated to an athlete’s training plan to make race preparation more personalized, tailored for performance optimization, and safer. Biomarkers that may help athletes train fall into 3 general categories: nutrition, endurance, and training status. 


To ensure that triathletes are optimally engaged during each training session, it is important that they are able to maintain their physiological states at optimal and healthy status. Biomarker testing may play an important role in monitoring a triathlete’s physiological state. For example, to ensure proper nutritional status has been achieved, the following nutrition-related biomarkers may be monitored:



Hemoglobin A1C

Vitamin D

Vitamin E

Vitamin B12


Omega 3 and 6

These biomarkers are known to help an athlete evaluate if his or her nutrition is adequate, if nutrient deficiencies exist, and if the athlete is consuming the proper foods choices. The nutritional biomarkers evaluate levels of macronutrients (energy-containing molecules in circulation), micronutrients (vitamins and minerals) that serve as coenzymes in metabolic function, omega fatty acids, and hydration indicators.

For an Ironman triathlete who focuses on developing endurance strength and wants to achieve optimal strength conditioning for the long-distance Ironman races, specific biomarkers may provide useful physiological information that may complement his or her training regimen. Some of these biomarkers include:

  • Ferritin
  • Transferrin
  • Iron
  • Lactate Dehydrogenase (LD)
  • Vitamin B12

  • Folate
  • Serum Osmolality

    Endurance is limited by the body’s capacity to consume, transport, and utilize oxygen to fuel sustained oxidative metabolism during prolonged endurance events. Thus, biomarkers that focus on red blood cell functions and nutrients that support red blood cell replenishment may be/are relevant to endurance athletes. In addition, due to the high physiologic demands of high volumes of training required for the Ironman events, markers of immune health (which often time may be compromised during high volume and intensity training periods) may also complement the endurance and conditioning data so that greater clarity may be achieved in understanding a triathlete’s full physiologic state.

    As mentioned previously, long-distance Ironman training requires many months of preparation and commitment. During the training periods, a triathlete and the coach may want to understand at various time periods the internal physiological status of the athlete. Since an Ironman triathlete trains at high volume and intensities, adequate recovery is essential to facilitate adaptations from the chronic and acute physiological challenges of endurance and high intensity training. As such, training status markers provide valuable information associated with recovery status and repair needs for the body. More importantly, these markers provide performance insights for susceptibility to overtraining and suboptimal training adaptations and if the triathlete may need to taper training to achieve higher level of performance. Some of these training status biomarkers include:

    • Creatine Kinase
    • Interleukin-6
    • Testosterone
    • Cortisol
    • Immunoglobulin A (IgA)
    • Thyroid (TSH)
    • Iron

    Commercial testing services that provide sports performance biomarker testing are available. An example is a UK-based company that provides simple, direct-to-consumer biomarker testing kits for athletes. Kits are purchased online and self-collected biological samples are returned using a prepaid package. Turnaround times are short and customers are provided with a laboratory report that includes an explanation of the biomarkers, biomarker data and interpretation, and perhaps most important, actionable insights to consider for assimilation into race training.

    For IRONMAN triathletes who are dedicating long periods of time, energy, and financial resources to training and preparing for high endurance races, sports biomarker insights may help enhance training and race-day performance, thus providing a competitive advantage over others engaged in conventional training regimens. Personalized biomarker data may help optimize training regimens and schedules that are strategic in terms of physiological status, such as those related to recovery and adaptation. This may improve the quality of training sessions and increase the endurance performance during race days. Likewise, knowing when to go easy and allow the body to rest and recover may ensure that a triathlete avoids season-ending injuries. 

    Despite the potential utility of sports biomarker testing for Ironman triathletes and others engaged in high-endurance type sports, certain considerations challenge its adoption. First, testing can be cost-prohibitive for the average triathlete. The average base cost for sports biomarker panels cost upwards of hundreds of dollars and is an out-of-pocket expense. Second, an average age-group triathlete does not perceive the added value of biomarker testing because he or she is unable to gain actionable insights that are easy to understand and implement into training. Frequently, testing reports are difficult to interpret, too scientific, and contain no actionable insights that add value to a triathlete’s training regimen. Furthermore, sports biomarker testing does not benefit a triathlete if it is only performed once. The frequency and schedule of testing should be considered and integrated into an individualized training schedule. This requires commitments from both the athlete and coach, in addition to guidance in translating physiological insights into actions that are safe and beneficial for the athlete in training. Finally, the benefit of sports biomarker testing is currently investigational and until further scientific evidence indicates the direct benefit of testing on performance outcomes, it is difficult to justify the added cost of testing to a sport that is already cost prohibitive for most amateur triathletes.

    Although challenges to the adoption of sports biomarker testing among amateur and competitive-level triathletes exist, growth potential and an opportunity to play a significant role in high-endurance race preparation and training also exist. With the advancement of sports wearables and increased interest in training customization, a personalized, low-cost, easy to understand, and actionable tool such as biomarker test panel will enable endurance triathletes to attain greater returns on training in the form of racing success.

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