Take your pulse during your workout to determine whether or not you're getting the cardiovascular benefit. Use either your carotid artery (neck) or your radial artery (wrist). Make sure you are at least 10 minutes into your workout. Count for 6 seconds, then put a zero on the end of the number. The number you get should fall in your target heart rate zone. The simplest way to calculate your THRzone is:
220 - (your age) = ____ (I'm 36, so 220 - 36 = 184)
Take that ____ x .6 (for me, 184 X .6 = 115)
Take that ____ X .8 (for me, 184 X .8 = 147)
In other words, when I am working out...ten minutes into my workout when I take my pulse I should get a number between 115 - 147.
This is an extremely simplified way to determine if you're getting a workout, but it is a good start. If you don't get your bottom number - work harder (go faster, use your arms more, increase intensity). If you don't sweat much - yay you!!! I sweat like a hog!