ignoramus7955 said:There is no guideline that says that heart rate should not go above
80% MHR, without qualifiers. Many people train at varied intensities,
sometimes at higher HR, sometimes lower. The suggestions to not go
above 80% MHR usually apply to notions like "fat burning" etc. They
say "if you want X, then do not run at above 80% MHR". Where X can be
"fat burning".
There is a common sense guideline that one should not go above 90% (of the true
MHR, not 220-age) without medical evaluation. This is particularly true of
people who take up running (or any competitive sport) later in life, or have a
family history of CHD or high blood pressure. For some of these people,
exercising above 90% (or weightlifting at a high % of 1RM) can be dangerous.
Other than this, there is no reason one cannot run at 100% MHR, except that you
cannot maintain it very long (this is a negative, if the purpose for running is
weight loss and not racing for performance).
Lyndon
"Speed Kills...It kills those that don't have it!" --US Olympic Track Coach
Brooks Johnson