How to Determine your Exercise Intensity
You can determine and program your exercise intensity by using metabolic equivalents or METS.
Popular Metabolic Equivalents
One MET is equal to 3.5 ml x kg ^-1 x min ^-1 of oxygen consumption. A MET is simply the amount of oxygen your body would need at rest.
For almost any activity you can think of from house work, to video game playing, to olympic lifting has a defined MET. For example walking at 4.5 miles/hour would be 6.3 METs, so you are using about 6.3 times more oxygen walking then you would if you were at rest.