What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes?
https://www.researchgate.net/publication/46403553_What_is_Best_Practice_for_Training_Intensity_and_Duration_Distribution_in_Endurance_Athletes

Training Intensity Distribution
https://www.researchgate.net/publication/235699324_Training_Intensity_Distribution

Polarised training with Stephen Seiler, PhD | EP#177
https://scientifictriathlon.com/tts177/

Polarised training: is it better than the Goldilocks approach?https://www.peakendurancesport.com/endurance-training/training-structure-and-planning/polarised-training-goldilocks-approach-training-intensity-wrong/

Thyroid Hormonal Responses to Intensive Interval Versus Steady-State Endurance Exercise Sessionshttps://pubmed.ncbi.nlm.nih.gov/22450344/