I disagree that the statement can be made that 160-170 for the whole run is appropriate. First it depend on your max heart rate. Mine is late 170's so even though I can actually talk at say 165, I am reaching an anaerobic stage. I can actually talk pretty well upto 170 believe it or not, and I have been tested for my max HR, so it was not a guess. Doc, you may have a much higher max than me, so if 160-170 is your zone 3-4 for example, then this works for you, but cannot be predicted for another athlete.

Even if you are not yet anaerobic, you are always then running in your highest zones, so later attempts at trying to run at lower aerobic zones, or to train for longer runs will be difficult. Second, you need to learn how to train where you manage your exertion throughout the duration of your event. You cannot maintain your highest zone (say zone 4-5) or high on the RPE scale for very extended sessions....you need to learn how to manage your HR during long endurance sessions and ensure you can maintain a good aerobic pace thru the entire event/race/etc. The more time you spend anaerobic and beyond your lactate threshold, the higher risk for burnout...management of this is crucial.

I am also a believer that one does not train for the end goal only, so you would not necessarily train for a 5K and never further -- you train right for running and then you should be able to scale up (or down) your efforts for longer (or shorter) races. Managing your heart rate over multiple zones throughout a race is a tested predictor of success and wins. Not saying you don't go anearobic or hit your max in a race event, but in most cases, unless you are a physical anomoly, you cannot sustain Zone 4-5 heart rates exclusively on all your runs, esp all your training runs. You will burn out and you will not be training yourself correctly.

If you are interested, authors and endurance runners Stu Mittleman and Phil Maffetone and have some good reading on the subject.

Sorry, I respectfully disagree on this subject as I believe HR monitoring is one of the best things you can do to train your body as well as improve your goals, whether they be burn fat, get in shape, train for a marathon etc. RPE (rate of perceived exertion) is subjective by its nature and therefore prone to error, and most people are not actually accurate in their predictions of HR via RPE.

Everyone finds it funny (well, my non-cyclist friends) that Lance is not ahead of the pack in every race, at the start of the race. Rather he paces himself, to avoid burnout, and uses his max capabilities and high zones where they are most needed -- up the mountain stages, at the line, etc. This is management of HR monitoring and its related impacts to your performance.

Sorry for the long winded response, I am a little "passionate" on this subject.... I was subject to poor training concepts early on in cycling many many years ago and it was not til I trained right that I saw vast improvements in my performance and studied it further from that point forward.