What is INSCYD?

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Most of us are familiar with using a threshold heart rate or pace to prescribe training zones. A simple ramp protocol or 20 minute power test has been the standard for training over the past several years. Fortunately a new system has been created to define more than threshold.

INSCYD was developed to look deep into the physiology of an athlete. The INSCYD program was conceived by sports scientist and cycling coach Sebastian Weber. Sebastian has worked though more than 150 studies as well as his own personal research to developed a new way of testing athletes. This test produces more than one metric and breaks down your physiology on all levels. You can learn more about the history of the test on their website here.

INSCYD assesses metabolic efficiency across different energy systems and fueling sources

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  • VO2Max - Aerobic Capacity

  • VLAMax - Glycolytic Capacity

  • Anaerobic Threshold

  • Economy

  • Fat Combustion (FATmax)

  • Carbohydrate Combustion (CarbMax)

By assessing these metrics an athlete is able to define more accurate training zones, asses training progress over time, create more accurate fueling strategies and define physiologic strengths and weaknesses.

One of the most valuable aspects of the program is its ability to define substrate utilization across different zones. This allows an athlete to understand how many carbohydrates versus how much fat he or she is using at a given output. This is invaluable for fueling strategies as well as program design. If an athlete is predominately a carbohydrate burner but wishes to improve their Half Ironman time then he or she would certainly need to develop their ability to burn fat more efficiently in return sparring more carbohydrate. This might mean more easy miles utilizing the FATmax zone. While the idea of polarized training is nothing new, it is easier to slow yourself down when you can see measurable results in your body’s ability to burn fat.


Alongside substrate utilization INSCYD can help tell wether a runner or swimmer needs to work on their physiology or improve technique to boost economy. By understanding pacing at a given output an athlete can see what percentage of their max output he or she is using. The goal is to maintain the same speed but use a lower percentage of max power or pace. Some athletes may have a very economical stride meaning they have a lower energy cost to maintain speed where as another may be able to hold the same pace but requires a much higher percentage of max, even if both athletes have the same maximum output. The infographic explains how three different athletes with similar physiology can have such different race times based on their economy. The good news is that with quarterly, annual, or bi-annual testing an athlete can track improvements in both physiology and economy. Perhaps VO2 did not increase but an athlete is still able to improve their time by boosting economy through strength training or running drills. The opposite may also be true. Without the data there is no way to know which parts of training are really paying off the most. By understanding where an athletes strengths and deficiencies lie coaches and athletes are able to maximize training time by focusing on what is needed most.

We are excited to be able to offer this testing program. INSCYD has only recently been opened up to the public and has become more accurate and robust since it was first released in 2017. We are one of the first and only labs to offer this protocol in the Southeast. The test itself is time efficient and doesn’t require you to spend too much time in the pain cave, only the final couple of stages. We have received excellent feedback from the athletes we have tested thus far and look forward to helping many more fine tune their training.

If you are interested in learning about INSCYD or scheduling a test you can read more on our service page here.

If you would like to read more about the metrics, benefits, and background you can find a wealth of information on their website here.

Patrick Morris