Quote:
Originally Posted by
Gradstudent78 
It's a good way to accurately guage aerobic intensity of a workout and track it over time. It's certainly not a necessity, but it can be helpful for people who tend to slack off without some kind of signal telling them to work harder.
Edit: Too long didn't read version: you don't need it, but there are reasons to use it, generally falling into "anal retentive" territory. Or if you want to specifically work at certain percents. For example, if you've ever done VO2 max testing, you get a sheet that says: 10mph 65% HR (140) 60% VO2 .01 mmol/L Lactate 12 mph 75% HR (160) 70% VO2 .08 mmol/L Lactate (you stop taking Lactate tests here...) 15 mph (failure) 100% HR (200) (I just guessed, these aren't right) 100% VO2 .13 peak Lactate Most important is the one at .8mmol/L lactate (IIRC), because that's the Aerobic/Anaerobic threshold, which is really good training. Run/swim/bike at your lactate threshold and you won't die by running out of O2, you get enough to barely keep going until your muscles are pumping battery acid. Great speed endurance and mental training, which you probably don't need unless you are competing in something. So you can judge that threshold by other cues (speed, etc) or by HR (more accurate, esp if, say, there's a hill, or you are on a bike and there's a tailwind, etc). And if you need to limit your training to, say, 3 hours a day because that's all the time you have, or that's all the mileage that you're allowed (max 10% increase year to year generally once up to speed), you need to train as efficiently as possible. Now, more practically, my HRM is attached to a GPS, so I know what my pace is, and its not like I mind having the chest strap on... except I lost my charger so I stopped using it.