From Fellrnr.com, Running tips
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* Like any new training routine, start off slowly and build up both duration and intensity over time.
* Be aware of how you are feeling and avoid pushing hard.
* Build up to exercising at 50% VO2max or above<ref name="Armstron1991"/>. 50% of VO2max is about 70% of maximum heart rate<ref name="swain"/> or "very slow running"<ref name="brianmac"/>.
* Use gradually increasing periods from 30 to 100 minutes over 10 to 14 days<ref name="Shapiro"/>
* Acclimation is fully developed after 7 to 14 days<ref name="Armstron1991"/>, but up to 75% of acclimation is reached after 5 days <ref name="Shapiro"/>.