Heart Rate Monitors: Magic Pill or Expensive Toy?

©1997 Dave McGovern--Dave's World Class

A fellow coach recently wrote a "What the Hell’s the Use" piece on heart rate monitors for the local running club newsletter. He opinied that athletes should just run slow on their easy days, and run fast on their hard days, and they don’t need a $200 gizmo to tell them that. But most of the athletes that I work with have never had the benefit of a coach, and now do the majority of their training alone. Many are experiencing the joy of athletics for the first time, and don’t know how hard a "hard" workout should feel or how easy an "easy" day should be. As a result, most push too hard on the easy days, which leaves them too tired to push hard enough on the hard days. It is exactly this type of athlete that can benefit most from a heart rate monitor.

What are They?

With each beat, the heart generates electrical signals that can be measured on the skin. A heart rate monitor transmitter contains two electrodes to detect these signals. The electrodes are mounted on a sealed transmitter that’s attached to the chest with an elastic belt. The transmitter detects the voltage differential on the skin during every heart beat and relays the signal to a wrist receiver which displays heart rate in beats per minute.

Dr. Seppo "Say it Three Times Fast" Saynajakangas produced the first portable heart rate monitors in Finland in 1982, and by 1990 Polar was distributing a full line of inexpensive models to the US and world markets. Today, several manufacturers produce monitors for under $100, which makes them accessible to even recreational athletes.

Why Bother?

The human body is a lot like a hybrid car that can create energy through a number of different systems. But instead of using solar panels, natural gas and ethanol, we create energ through fat burning and aerobic glycolysis when racewalking slowly, by anaerobic glycolysis (the"lactate system") whenmoving at a faster pace, and through the creatine phosphatase system when sprinting. Pace and duration of activity determine which system predominates. The body tends to utilize the most efficient system available, but some "fuels" are more efficient or more plentiful in the body than others: Glycogen is limited and can be depleted within 90 minutes of hard work, while fat exists in the body in nearly limitless quantities.

The downside to utilizing fat as an energy source is that it can only be burned in the presence of both oxygen and glycogen (intra-muscular or blood sugar). So despite its high caloric potential--about 9 calories per gram--fat combustion wastes a lot of oxygen. Glycogen’s drawback--in addition to its limited quantities within the body--is that it’s your body’s equivalent of a "diesel" engine: It’s a reliable fuel source under a variety of conditions, but when oxygen is limited it’s "dirty" as Hell. But instead of spewing smog, your anaerobic glycolysis "engine" spits out buckets of nasty lactic acid. Ultimately, availability of oxygen will always dictate how energy will be produced, and how "clean" the combustion will be.

In any race over 3K, most energy is produced aerobically. So the bulk of training should be easy, aerobic distance work. Too much speed work, or too many hard miles on the roads will teach the muscles to rely on anaerobic glycolysis, resulting in excess lactate production when racing. But most people tend to push too hard on their easy days without realizing it.

Physiologists can determine how much is too much by measuring inhaled oxygen and exhaled carbon dioxide. This is the only direct way to determine how energy is being produced, but the equipment is very bulky so the tests can only be performed in a laboratory setting--on a treadmill with the athlete hooked up to what looks like a cross between a welder’s helmet and Mom’s vacuum cleaner--Not the kind of thing you’d want to wear during your next 5 km race.

Luckily there’s an easier way: All that inhaled oxygen has to get to the working muscles somehow, and it does so dissolved in the blood, pumped throughout the body by the heart. As oxygen needs increase, heart rate increases--in lock-step with respiration rate. Heart rate, then, is a very reliable--albeit indirect--indicator of oxygen use. That’s why the Neanderthals (back in the 60s and 70s) used to stop to take their pulse during workouts. But who wants to stop in the middle of a workout to poke around looking for the carotid artery? By the time you find the thing, then count to six or ten, your pulse has dropped 20 beats anyway, rendering the results meaningless.

How to Use a Heart Rate Monitor

There are a number of different ways a heart rate monitor can be used in training and racing:

1. As an Equalizer. External factors such as heat, humidity, altitude and wind, and internal factors like dehydration, fatigue and psychological stress can profoundly affect an athlete’s ability to perform. Ignoring these factors by attempting to train at a set pace per mile under difficult conditions can lead to overtraining. A heart rate monitor allows you to train at an even effort under any conditions.

2. As a Governor. Sometimes it’s hard to go easy. A monitor can ensure that LSD is long slow distance and recovery days are recovery days. It can also ensure that you don’t go nuts in the first 400 meters of a race. There’s no such thing as "free" energy: If you go out too hard at the start, it’ll get you in the end. Remember the Tortoise and the Hare? (Hint: The Turtle wins.)

3. As a Butt-Kicker. Sorry, but there are also days when you have to work really hard to get fitter. A heart rate monitor can ensure that you’re sustaining an 85% effort on those tempo workouts, or 90 to 95% when doing hard intervals.

4. As a Diagnostician. Keeping track of morning heart rate can give you forewarning if you’re over-trained. If your resting heart rate is 5 to 8 beats per minute higher than normal, it’s time to back off: You’re overtrained.

Whether you’re just beginning a walking program for weight loss or fitness, or an elite-level racewalker, you can benefit from a heart rate monitor’s ability to keep you motivated, under control, and "in the zone."

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