interval training

Exercise Physiology for Interval Training in Indoor Cycling, Part 2

Jennifer Sage and Jennifer Klau, PhD, teamed up to write this series on interval training. Dr. Klau will ensure that we include the latest scientific knowledge so instructors will know this is the most up-to-date information on interval training available. At the start of every post, we will include a glossary for easy reference. 




Aerobic: Using oxygen

Anaerobic: Without oxygen

Glycolysis: 10-step cycle that breaks down glucose into energy. Can operate aerobically or anaerobically

TCA/Krebs Cycle: Intermediate cycle in the aerobic pathway between glycolysis and ETC

ETC: Electron transport chain. Final sequence of aerobic pathway, site of actual O2 use

LT: Lactate threshold. Exercise intensity at which lactate production exceeds lactate clearance

VO2 Max: Maximum rate at which O2 can be taken up and used by the body. Expressed in either L・kg -1 (absolute)  or ml・kg・min -1 (relative, allows comparison between individuals). Considered a predictor of endurance performance, upper limits are genetically constrained, training can only increase this to the genetic limit.

Exercise Physiology for Interval Training: Part 2

Part 1 covered the aerobic system and ATP-CP. In this segment, we cover the lactate system, lactate threshold, and VO2 max.

The Lactate System

In our next article, we will discuss lactate threshold training, probably the single most important element of your fitness that you can improve.

Additional Resources:



  1. Thank you so much for this info! I agree also, as part of most of my certifications a long time ago, they always included an exercise physiology portion.. seems the certs are watered down now and much shorter. I would love to be able to include this article in a training manual I am doing for a cycling studio … Would that be possible with proper acknowledgement and siting?

    thank you!

  2. This is fantastic information. Thank you for sharing your knowledge with ICA members in this series. In my opinion, this type of education should be an integral part of any indoor cycling certification. I had to learn it, and was tested on my knowledge, in order to become a certified running coach. Registered yoga teachers must learn the details of anatomy in order to get their RYT200 cert. Basic knowledge of exercise physiology and the energy systems is far more important for indoor cycling instructors than knowing the best Katy Perry song to play for warm up.

    1. Author

      Thanks, Bill. I agree that this info is really important (and not just because I’m a geek). And, in case anyone is wondering about that last point, the answer is none, Katy Perry is terrible for warm up. 😉

  3. Great series so far. Thank you, Jennifer and Jennifer!

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