Pulse Rate Monitors

by Patti and Warren Finke, Team Oregon
The development of portable light weight pulse rate monitors is a technological advance that holds great promise as a tool for training endurance athletes. Many coaches, including us, were skeptical at the introduction of new "high tech toys". Now we have three years experience using these monitors to train runners, including ourselves, and are convinced of their value . A pulse rate monitor can be a powerful tool IF YOU KNOW HOW TO USE IT.

How Pulse Rate Monitors Work

There are several different types of pulse rate monitors on the market. They use various techniques for detecting pulse rates. Most of them are either optical ( sensing blood flow through your finger) or electrical ( sensing the electrical signals that your heart generates when it beats).

The only dependable monitors that we have seen use electrical sensors. Normally, this type of monitor has two electrodes that must be placed in contact with the skin on your chest. The sensor communicates by wire or low energy radio signal with an electronics package that contains a microprocessor, for computing pulse rate and other functions, and a display. The most notable examples of this type of monitor are those made by a Finnish company POLAR. These use a chest belt with electrodes and a transmitter and a digital watch-like receiver/computer/display.

Why Pulse Rate is Significant

Early exercise physiology research found that heart rate increased with increasing intensity of exercise. This is not a surprise since the body requires oxygen to do work, and that oxygen is supplied by the blood pumped by the heart. The harder you work, the more oxygen is needed and the faster your heart beats to supply the oxygen. Within the range between your resting and maximum pulse rate, ( known as heart rate reserve), heart rate increases linearly with oxygen consumption (VO2) and exercise intensity. Thus, heart rate gives you a direct measurement of how hard you are working. The figure illustrates pulse rate response during exercise for a typical trained 35 year old.

Resting and Maximum Pulse Rates

To be able to use your pulse rate as an indicator of how hard you are working, it is important to know both your resting and maximum pulse rates. Your level of effort is determined by where your pulse rate is in this range.

In addition to other factors, maximum pulse rate depends on age. Estimates of maximum pulse rate are often done using the formula max HR(heart rate) = 220 - age. This may be good indication of your max. Whether maximum heart rate declines or increases with continual training is a current controversy in exercise physiology. We have seen both responses and runners who differ radically from the predicted formula. Max pulse rate can be determined in a maximal stress test. A max test is expensive since it needs to be done with a physician present; also the test was designed to pick up and monitor heart disease. Certainly a submaximal stress test and/or physicians check up is important for beginning runners over 40. The best way to determine maximum pulse rate for young and/or experienced runners is to measure pulse rate during a maximal effort race of about 2 miles. We have developed some submaximal measurement techniques we can use on runners with previous race performances.

Resting pulse rate is an indicator of stroke volume which is the amount of blood pumped by each beat of the heart. Stroke volume of well-trained individuals is generally much higher than in the untrained populace. Endurance athletes often have resting pulse rates in the 30s and 40s. A large heart rate reserve ( range of pumping speed) and a large stroke volume are prerequisites for performance in endurance sports. You can determine your resting pulse rate by taking your pulse first thing in the morning when you are relaxed. Take your pulse for several days and use the average for your resting pulse.

Classic Uses of Pulse Rates for Training

The best known technique is the so-called Target Heart Rate Zone. In the 80's, exercise physiologists thought that training took place between 70% and 90% of maximum heart rate. This measurement was often referred to as the Target Heart Rate Zone for training. The 70% level was even called the threshold for training effect. We now know that some training effect probably takes place at all levels above rest. Also, the percentage of heart rate reserve is a better gauge of intensity than the simple percentage of heart rate maximum.

Early techniques of specifying a broad zone (70%-90%) were not very helpful to the athlete because the range of intensity encompasses nearly every training speed imaginable. 90%, for instance, is near 10K race effort, while an easy 10 mile training run is about 70%. Additionally, target zones were often used without regard to the goals of the training. Goals are radically different for those interested in fitness and weight loss versus competitive distance running.

The worst problem with dictating a training zone is that it is often done without consideration of the duration of the exercise. To show this, in the figure below we have graphed the estimated average pulse rate a 35 year old could maintain for different race distances. All these pulse rates represent a 100% effort for the distance. However, since you cannot maintain the same speed racing at longer distances, there is a 15% difference in the speed and in the pulse rates.

What we Know Now

Distance Based Intensity

It is not enough to simply look at intensity when we gauge the training stress or benefits of exercise. This should be clear from the fatigue levels felt after racing different distances, and the demonstrated effectiveness of long slow distance training for endurance events.

Intensity needs to be measured in the context of the duration of the exercise. This is an important and different way of measuring intensity. When we measure intensity in this way, 100% means race pace at the distance we are running.

We know that paces fall off about 5% every time you double the race distance, and so does your average heart rate.

We have found that significant endurance training effect takes place if you run at 60% of the pace you could do over the same distance in a race. 80% pace is the maximum runners can maintain for a training run and still perceive it as easy effort. At 85%- 90% workouts are no longer fun for most of us.

We have used this distance based intensity idea for many years to determine the training paces of the athletes we coach. A natural extension of it is to figure out target heart rates based on the same approach. In the figure below we have done this for the 80% effort target heart rates of a 35 year old over various training distances. 80% would be the highest you would want your pulse to be for an "easy" run.

Specificity

Although the bulk of an endurance athletes training, ( long runs, easy days, and base building), should be done below 80% effort, it is important to do specific training for the events you wish to compete in. This means you should do some training that uses the energy systems you will require and some training that to make you efficient at your race pace.

The use of various energy systems is affected directly by intensity. Stressing the lactate system, (used in short road races) requires training intensities in the 90%-95% region. Optimizing fat metabolism, (needed for marathon and ultra events), requires intensities of 70% or lower. Heart rate provides an excellent means for determining which fuel system "zone" you are in.

Efficiency can be trained by doing some running, (tempo runs or repeats), at race intensity. Often you do not know what your potential race pace is when you are training. But if you know what your heart rate should be for that race distance, you can use the pulse rate monitor to set your level of effort for your training runs. As you work into shape you can measure your improvement in speed and gauge your potential race times.

Target Pulse Rates for Training

Below we have listed some target racing and training pulse rates for runners of different ages. These assume an average resting HR for a healthy runner and max HR for your age. If you have measured your maximum HR use the closest column instead and ignore the age.

If you want some coaching using this system, you can join us for a Team Oregon Training Session.

                             RACING AND TRAINING PULSES

          AGE:                23   31   39   46   52   59   65
          max heart rate      196  188  181  174  167  161  155
          5 km race pace      191  184  177  170  163  157  151
          10 km race pace     184  177  170  164  157  152  146
          20 km race pace     177  171  164  158  152  146  141
          marathon race pace  170  164  158  152  146  141  136
          easy 5 mi training  <156 <150 <145 <140 <135 <130 <126
          easy 20 mi training <150 <144 <139 <134 <130 <125 <121
          fat burning         <155 <149 <143 <138 <133 <129 <124
          lactate system use  >181 >174 >167 >161 >155 >149 >143

Use the race pace pulses for tempo runs or long repeats to simulate race intensity. You can also use them during a race to keep yourself from starting too fast. A good interval workout for road races < 10 km is to first warm up for a mile and then alternate hard running until you exceed the lactate system use pulse with easy running until your pulse falls below the fat burning number.

Racing With a Pulse Rate Monitor

A pulse rate monitor can be invaluable for runners who have difficulty judging effort during competion. It also provides a worry free approach to racing when you don't know your current fitness level, the race is long and you need to ration your strength, or the race is hilly or has other stressful aspects difficult to plan paces for. You simply use a target heart rate for the race and attempt to maintain it by slowing down or speeding up as necessary. The figure below shows a runners pulse rate response using this technique during the 1994 hilly and hot Hagg Lake 10.4 mile road race. The runners goal was to maintain a heart rate of 165 throughout the race. This would require the runner to adjust his speed, slowing on the uphill and accelerating on the downhill. In practice, you are doing a good job of this if you can keep your pulse to +/- 5 beats from the target. If you are an inexperienced hill runner this means slowing more than you might normally on the uphills and running much faster on the downhills. In this case the runner did a good job of maintaining even effort with the exception of running the first hill, (at around 6 minutes), too hard.

Caveats

As mentioned before, it is important to establish your personal pulse rate responses. If the numbers in the table above for your age don't seem to match your maximum pulse rate, then determine what it really is and figure your training numbers out based on your max.

Medication can affect heart rate. If you are taking oral asthma, blood pressure, thyroid or heart regulating drugs, discuss the possible effects to resting and training pulse rates with your physician. Any unusual heart rate response should be checked out by your physician.

Heart rate is affected by temperature, rising with high or low temperatures that require your body to use additional energy for temperature regulation. It is also affected by stress or illness. All these effects act like an elevated resting heart rate. This means that your sub maximal heart rates will be higher than they would be under normal conditions and you will have less Heart Rate Reserve with which to run.

If you are training in extreme temperatures you can take this into account by allowing slightly higher training pulse rates. Our personal experiences training in Hawaii part of the year are that resting pulses seem to be 10 - 20 beats higher. Training at the same perceived effort results in pulses about 10 beats higher than what we measure in Oregon.

If you are not being affected by temperature and your pulse rate is much different from your perceived exertion, it is our opinion that you are better off to use the pulse rate monitor and err on the side of conservatism. Often perceived exertion is the runner's worst enemy. You may be fatigued or stressed by many outside factors.

Make sure you are warmed up before you use your pulse rate monitor to gauge your intensity. It often takes 10 minutes or so to get to steady state at training efforts. During this period your heart rate may be lower than during the rest of the run.

Your heart rate will also lag when you start running at high intensity. It may take 300 to 400 meters on the track before your heart has responded making the monitor of little use measuring the intensity of short intervals. The best way to use the monitor for this type of workout is to monitor recovery and to detect when your recovery is waning, (time to quit and do a cooldown).


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