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* A 2007 randomly assigned 12 sub-elite 5K & cross country runners to one of two training programs<ref name="Esteve-Lanao-2007"/>. The Z1 program had 80% LSD, 10% Tempo, and 10% HIIT, whereas the Z2 program had 65% LSD, 25% Tempo, and 10% HIIT. The Z1 group that did less time at Tempo pace improved their race performance more than the Z2 group. (Their simulated 10K times improved 35 seconds more, 157 second improvement rather than 121 second improvement.)

* A 2009 review of the science of training intensity noted that recreational runners typically fall into a "black hole" of too much Lactate Threshold running<ref name="Seiler-2009"/>. They noted "''Training intended to be longer and slower becomes too fast and shorter in duration, and interval training fails to reach the desired intensity. The result is that most training sessions end up being performed at the same threshold intensity''."

* Polarized training has been shown to be more effective than high volume/low intensity, threshold/tempo, or [[High Intensity Interval Training]]<ref name="StögglSperlich2014"/>. The polarized training used two [[High Intensity Interval Training]] and two long (150-240 minute) low intensity sessions.

* It has been observed that elite athletes exercise 80% of the time at low intensity (blood lactate < 2 mmol/l) and 20% of the time at Lactate Threshold or [[High Intensity Interval Training]]<ref name="Seiler-2010"/>. (Sadly this study did not have any breakdown between Lactate Threshold or [[High Intensity Interval Training]].)