Karate Athlete - Heart Rate Monitors

Introduction

Training techniques and programs have become increasingly more sophisticated in recent years. Advanced technology regarding the food, clothing, and equipment best suited to aid athletic performance have seemingly transformed sport into as much a scientific endeavor as a physical endeavor.

Among the instruments that have gained popularity for use by athletes is the heart rate monitor. Many coaches, scientists, and athletes feel strongly that training "by the numbers" (i.e., monitoring one's heart rate) can significantly impact on physical performance. On the other hand, there are those who question the validity of measuring heart rate during exercise, and some experts warn that an over reliance on target heart-rate zones can lead to erroneous conclusions about the intensity of training.

The Gatorade Sports Science Institute polled four experts on their opinions regarding this very practical and yet controversial issue. Their answers to our questions follow.

WHY DO YOU THINK THAT THE USE OF HEART RATE MONITORS HAS INCREASED AMONG ATHLETES?

Maughan : Reliable lightweight telemetry systems (heart-rate monitors) have only become available at a reasonable cost within the last few years. Prior to that, the cost for an often-times unreliable monitor was likely to run into thousands of dollars. For some reason, heart-rate monitors are particularly popular among cyclists. In fact, the British Cycling Federation has issued training guidelines for riders which recognize four different training levels based on heart-rate responses. Because many, if not most of the top riders use these monitors to quantify their training, they have become fashionable. I'm not sure why they have become so popular among elite riders, but there is a strong feeling that they can help to quantify the training load, and make the training pro-gram more "scientific". There certainly is a novelty value to them, which may help to avoid psychological staleness.

Burke : I do see a value to the use of heart-rate monitors. On any given day, many environmental and physiological variables can affect the intensity of an athlete's effort in training or competition. Factors such as air temperature, wind, humidity, and terrain can vary from workout to workout and affect the amount of effort that athletes have to put forth. Heart-rate monitors have enabled athletes to measure accurately their effort by recording one key physiological response to exercise. They provide an accurate gauge of the intensity of each exercise session, regardless of the training environment or other outside stresses on the body.

Daniels : I'm inclined to agree with Dr. Maughan's assessment of heart rate monitors as a novelty. As a coach who has trained numerous athletes, I realize that athletes will try anything to get an edge on an opponent, or to keep up with what they think somebody else might be doing. In most cases effective training does not require the use of a heart rate monitor. Furthermore, if we are to assume that monitoring heart rate is a useful thing for an athlete to do, I don't think that a heart rate monitor is better than manually counting heart rate with a watch.

Coyle : Because they provide instant feedback about the cardiovascular stress experienced during exercise, they are fun tools.

By the nature of their sport, endurance athletes are very "tuned into" numbers regarding time, distance and, thus, pace. Heart rate monitors satisfy this need for quantification by providing feedback regarding the body's response to the stress of training and racing.

HOW DO ATHLETES TYPICALLY USE HEART RATE MONITORS ?

Coyle : Athletes typically use heart rate monitors to fine-tune the intensity at which they are training and racing. Having spent years running track, I still think that training pace is best set using a simple stop watch to time pace over accurately measured distances. Pool swimmers also rely heavily on the stop watch. However, in sports such as bicycling and rowing, pace is greatly influenced by the environmental factors that Dr. Burke alluded to. In these cases the athlete is better off looking at heart rate to select pace.

The first step in using a monitor is for the athlete to determine his/her maximal heart rate, and to calculate the heart rates corresponding to 80, 85, 90 and 95% of maximal heart rate. Athletes should then determine the duration of exercise that can be maintained at these intensities while also determining the pace that elicits maximal heart rate. This relationship can be used to help establish training and racing paces along with other measures.

Monitors can also be used to judge improvements in cardiovascular function with training, especially during the first few months of a training program. As people become more fit, heart rate declines for a given pace. I recommend that after every 2-3 weeks of training and after a couple of days of rest or easy training, athletes record their heart rate at a predetermined pace. The duration of the exercise should be 5-10 minutes at a hard but constant intensity. The declines in heart rate at this given pace are an indication that cardiovascular improvements have occurred.

Burke : There are many different ways to monitor training, but monitoring heart-rate response is the simplest, most-convenient and least-expensive physiological method for monitoring training. Most athletes use a heart-rate monitor to get an accurate reading of their heart rate to ensure that they are reaching the goal of a particular workout. For example, if a person wants to exercise at an intensity slightly below lactate threshold they can set a narrow heart-rate target zone by setting the high- and low-alarm limits to provide audio and visual feedback I view wireless heart-rate monitors as essential training tools. Without them, training or competing in a particular heart rate zone is mere guesswork. It is like an architect working on a building without a ruler!

Maughan : I also believe that most athletes use heart-rate monitors primarily to regulate the intensity of effort in training. Furthermore, many cyclists use heart rate as a means of deciding the length of the recovery period during interval-training sessions--the next interval will not begin until heart rate has fallen to a predetermined level. Other athletes use heart-rate monitors to try to detect the early symptoms of illness or overtraining. If the heart rate is higher than expected for a given effort, this is taken to be a warning signal.

I am not convinced, however, of Dr. Burke's assertion that heart-rate monitors are an indispensable training tool. I am not aware of any evidence to show that athletes with heart-rate monitors perform better than those who do not use monitors, or that the effectiveness of their training is enhanced. Heart-rate monitors can provide motivation and feedback to those athletes that need it, but the scientific evidence supporting their use is not convincing.

IS THERE RESEARCH SUPPORTING THE USE OF HEART-RATE MONITORS BY ATHLETES?

Daniels : There is no research that I am aware of that directly supports the use of heart-rate monitors by athletes. There is certainly a relationship between heart rate and oxygen consumption (V02), and training intensities can be approximated by utilizing this relationship. However, the relationship established between heart rate and VO2 in a laboratory setting will not always hold under actual training or race conditions.

Coyle : Dr. Daniels raises a good point. The real question is whether heart rate itself is a valid measure of training state or intensity. The heart-rate monitor is merely a tool for counting and recording heart beats. Of course there is much research and many empirical observations demonstrating the sensitivity of heart rate to cardiovascular stress imposed by dehydration, deconditioning, insufficient sleep, reduction in blood volume, stress, and overtraining. We also use heart rate to tell us whether an athlete is rested enough to perform a hard training bout. Research conducted in the Netherlands suggests that heart rate during sleep may increase by about five beats per minute when an athlete is overtrained. Therefore, alterations in heart rate can detect when your body is adapting positively as well as negatively to training.

Burke : Regarding the accuracy of the monitor itself, the most critical feature is the means by which heart rate is detected. Detecting heart rate at the earlobe or fingertip via photo-optic techniques have proven to be unreliable. Portable wireless monitors are now available that can measure heart rates in the field with the accu-racy of expensive laboratory equipment. Several clinical studies have demonstrated that there is no significant difference in heart rate among athletes monitored by wireless monitors and large ECG units.

WHAT ARE THE LIMITATIONS OF USING HEART-RATE MONITORS?

Maughan : The first lesson that the athlete using a heart-rate monitor must learn is to treat the information which it gives with caution. Although maximum heart rate is generally recognized to be 220 beats minus age, this equation does not apply to everyone. We have seen well-trained endurance athletes in their thirties who could not achieve heart rates of 170 beats per minute. This is less than 90% of the expected maximum, and attempts to train at this heart rate would lead to frustration. Furthermore, there must also be a willingness to adopt a flexible approach to training. For example, there are advantages to runners and cyclists to train as a group; however, this is probably not possible if everyone must maintain a speed that is determined by their individual training heart rates.

Burke : As was mentioned earlier, heart rate can be affected by a wide range of factors, and athletes need to be aware of this when interpreting the meaning of their heart-rate information. For example, heart rate may cease to a be a reliable point of reference for measuring exercise intensity when one is exercising above 85% of VO2 max. Furthermore, maximum heart rate is sport specific. Maximal heart rate will be differ-ent for a triathlete in each of the disciplines of his sport: swimming, cycling, and running. Lastly, heart rate can be affected by changing environmental conditions and dehydration, as well as by altitude. All of these factors need to be taken into account when using target heart-rate zones.

Coyle : Information overload can be a major limitation of using a heart-rate monitor. Heart rate can only provide interpretable information for monitoring progress when it is carefully measured under standardized conditions. Time of day, body position, length of rest, behavior, mood, and timing of meals must all be controlled. That is why sleeping or "gentle waking" heart rate is often used a frame of reference.

Athletes should also keep in mind that heart rate reflects the average stress experienced over the last few minutes of exercise. When you increase exercise intensity or pace, it takes 15-30 seconds before heart rate increases substantially, and it will not stabilize at the new value for two-to-three minutes. In these transition periods, and in general, it is better to rely on cues such as feelings of fatigue when selecting a training pace, rather than heart rate.

WHAT ADVICE WOULD YOU GIVE TO AN ATHLETE WHO WANTED TO USE A HEART RATE MONITOR AS PART OF THEIR TRAINING ROUTINE?

Daniels : It would depend on the sport in which the athlete was participating. In situations when velocity of movement is not easily controlled, or when undulating terrain or adverse weather conditions may be a factor, heart rate monitors may be useful. In other cases, I'd likely tell the athlete to save his or her money.

Coyle : I'd tell an athlete to use it as a motivational tool when they train hard, or as a means of preventing overtraining during periods when they are supposed to be taking it easy. The heart-rate monitor is like a coach that keeps you on track. Most athletes who train by themselves tend to train too hard when they should be taking it easy, or they train too easy when they should be pushing it a bit more. Heart-rate monitors, like coaches, can be more objective than the athlete in assessing whether the objective of training is being met.

Burke : By monitoring heart rate accurately, an athlete can get more benefit out of the time spent training. The three most important variables in designing a training program are frequency, time, and intensity of training. The first two factors are easy to monitor, but intensity of training may be difficult to gauge. Recording training heart rate in a daily log can help to quantify this important training variable.

Maughan : For those taking up an exercise program or beginning serious training, there are probably real benefits in using a heart rate monitor during training. A common error of the novice is to train too hard; this can be avoided by monitoring heart rate. The feedback provided by seeing heart rate fall as a training program progresses is also a strong motivational factor for the novice athlete. The experienced athlete has probably learned to monitor his body's internal cues, and will not be as likely to benefit by using a heart rate monitor. Nevertheless, one can not discount the fact that requiring an athlete to assess and record daily training heart rates can give a coach insights into the athlete's response to a training session, as well as confirmation that the athlete actually carried out the exercise session.

Selected Readings

Ali, A. & Farrally, M. Recording soccer players' heart rates during matches, J. Sports Sci. 9:83-89, 1991

Gretebeck, R.J., Montoye, H., Bailor, D., & Montoye, A.P. Comment on heart rate recording in field studies, J. Sports Med. Phys. Fit. 31 (4):629-631, 1991

Jeukendrup, A.E., Hesselink, M.K.C., Snyder, A.C., Kuipers, H., & Keizer, H.A. Physiological changes in male competitive cyclists after two weeks of intensified training, Int J. Sports Med. 13:534-541, 1992

Leger, L. & Thiviege, M. Heart rate monitors: validity, stability, and functionality, Phys. & Sportsmed. 16 (5): 143-151, 1988

Macfarlane, D.J., Fogarty, B .A., & Hopkins, W.G. The accuracy and variability of commercially available heart rate monitors, N.Z.J. Sports Med. 17(4):51-53, 1989

Treiber, EA., Musante, L., Hartdagan, S., Davis, H., Levy, M., Strong, W.B. Validation of a heart rate monitor with children in laboratory and field settings, Med. Sci. Sports Exer. 21(3):338-342, 1989

The Sports Science Exchange Roundtable is moderated by Mitchell M. Kanter, Ph.D., Senior Research Scientist, Gatorade Exercise Physiology Laboratory.