Why Train With a Heart Rate Monitor?
(Aerobic and Anaerobic Fitness)
by Max Wettstein, Copyright 2005
Why train with a heart rate monitor, (HRM)?
The Polar 3 Point Message sums it up briefly:
Monique Ryan, MS, RD, founder of Personal Nutrition Designs, adds:
“When you train with a HRM it provides the feedback you require to perform the appropriate training session for that day in order to stay within a specific HR zone. It can also provide you with feedback on the mix of fuels, (carbs, fat, etc.), you would burn during exercise.”
A HRM is a tool that will help pace you and track your progress, and is light weight and easy to use. A thin, plastic, transmitting chest strap is worn around the sternum area, and a receiver watch is worn on the wrist, or if you’re a cyclist, you can mount the receiver on your handlebars. Polar is the most well known brand and is what I have been using for the past 4 years. The receiver serves a great water-resistant watch as well, and has all the other functions you would expect a watch to have.
You may be wondering if a HRM is really necessary for general health and fitness goals. Sure tri-athletes, high-risk individuals such as pregnant women, and other over-achieving gym rats use them, but why should you? Most of us have good intuition about how we feel and how hard we our exerting ourselves, and if we really want to know our HR we can always just take our own pulse and multiply it by a factor of time. But wouldn’t it be convenient to know it precisely and continuously during our entire workout without struggling with mental math? Sometimes we’ll go against our intuition as we try to achieve our normal intensity level or pace, not knowing we are not fully recovered from a previous training session, or perhaps fighting off a cold or virus. This can lead to a compromised immune system. A HRM will tell you exactly how intense you are working so you will know if you are feeling a little under the weather or are just slacking, or perhaps achieving a new personal best. What’s more, using an HRM can save us a lot of mental math. The latter is especially true if you are trying to exercise in a specific heart rate zone based on a percentage of your maximum heart rate, (MHR). A good HRM will calculate your MHR, give you a percentage read-out based off your current HR, and tell you exactly which fitness zone you are exercising in.
There are generally three fitness training zones based on percentage of your maximum heart rate, and these 3 different heart rate zones use different energy production systems in the body, and therefore different fuel source combinations, such as muscle-ATP/Creatine phosphate, muscle-glycogen, glucose, intra-muscular fat, and adipose tissue fat. Now stay with me because the physiology of energy production is an in-depth topic in itself and beyond the scope of this article and I intend to simplify matters greatly for the purposes of our discussion. In reality, most of the time when we exercise our HR varies across all of these zones, from aerobic to anaerobic, and therefore we produce energy in combination, burning carbs and fat simultaneously. There are exceptions, and with the aide of a HRM we can remain with-in a desired zone. So what the heck is a ‘zone’ anyway? Generally the three HR fitness zones for the purposes of training are:
(**Note: The above HR percentages are approximate and vary with personal fitness level and genetics.)
I hope you’re still with me, because that is as complicated as this article will get. Those three fitness HR zones and their respective energy production mechanisms have been greatly generalized, when in reality the zones merge and blend to a certain degree, and everyone’s threshold varies based on genetics and their current level of fitness. For example, you can raise your lactate threshold so that you can exercise at a higher HR for longer periods without becoming hypo-glycemic, or ‘bonking’, because you are able to recycle lactic acid more efficiently for extra fuel. Additionally, the more aerobically fit you become, your muscle cells will increase the size and number of their cell mitochondria, thus improving the cells’ capacity to use oxygen and increasing the amount oxygen the body can use in a given time, allowing you to remain aerobic at higher training intensities. Your heart muscle will strengthen enabling it to do less work to achieve the same level of efficiency; you’ll grow more capillaries improving blood supply to cells, and become more efficient at burning fat for fuel. Your muscles will become more tolerant of lactic acid and more resistant to fatigue, will become more insulin sensitive, and store glycogen more efficiently and in larger amounts.
All of these health benefits are accomplished through consistent aerobic and anaerobic fitness training for 6 months or longer, and using a HRM makes this a lot easier. Ultimately we are all genetically limited in how aerobically fit we can become, as this is pre-determined by a marker known as our maximal oxygen consumption plateau, or VO2 Max. This benchmark can only be determined by precise laboratory/blood testing while exercising, so most of us will probably never know where this level exists. Fortunately most of the newer, more advanced HRMs on the market now come with built-in fitness testing based on your age, gender, height, weight, estimated activity level, and resting HR, and will compute a fairly accurate VO2 Max, (in percentage of your MHR), eliminating the need for you to make an appt. over at the sports laboratory.
The whole point of knowing about HR training zones is so you know how to choose your intensity level to better achieve your specific fitness goal. For example, if fat loss/burning is your primary goal, as I’m sure it is for most of us, you would want to do long aerobic/endurance workouts keeping your HR around 60 to 70% of MHR. The good news is this intensity level is quickly and easily achieved, by fast-walking, slow-jogging, or easy cycling, etc. Sport’s scientists currently believe that it takes at least 20 minutes before you enter the ideal, ‘fat-burning zone’, however. This is because your heart, being a muscle needs to warm up before it performs at its aerobic optimum. Also, initially when exercise first begins, you tend to burn higher levels of glucose and muscle glycogen, (both forms of carbohydrate), and as those deplete, you will trigger more fatty acids to be released from your fat stores. Don’t lose sight of the bigger picture though: Any duration of exercise is better than nothing, even ten minutes, and ultimately at the end of the day it is calories that matter most. You must have created a calorie deficit in order to lose fat, no matter what zone you are exercising in. Fortunately most HRMs track caloric expenditure as well. Intense exercise also boosts your metabolism for longer afterwards. Although we are all motivated most by fat loss, occasionally you should fire up the intensity to maximize all health benefits.
Sources: Sports Nutrition for Endurance Athletes by Monique Ryan; The American Medical Association Medical Encyclopedia; www.polarusa.com
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