Apparently if you exercise hard for 150 minutes every week, that’s enough to keep you fit. You can even do it in 10 minute lots. For further information on this, read here
And to guage the effectiveness of an activity to count as exercise, don’t measure your heart rate, measure your metabolic rate. Scientists have organised a measure, called MET, to allocate to various activities. The bible for this is The Compendium of Physical Activities.
And yes, you can be fit even if you’re carrying extra weight. Read here for more information about this.
My information is from the New Scientist magazine – here’s the link to the entire article: http://www.newscientist.com/special/get-physical-nine-facts-about-fitness?DCMP=NLC-nletter&nsref=getphysical.
