(This article was originally published in Independant Rowing News August 28, 1998) Scientists and coaches are constantly trying to find better, more efficient ways of training. Sometimes, outdated or inaccurate methods continue to haunt a sport and may actually be detrimental to the development of the athlete. Such is the case with heart rate monitoring.
Heart rate is an easily measurable physiological variable that is often used to gauge the intensity of a training session. With the recent development of affordable, accurate monitors the popularity of heart rate monitoring has skyrocketed. While under the right conditions heart rates can be a useful tool there are too many athletes that have developed a dependence on their heart rate monitor. I would like to take this opportunity to exam some of the potential problems associated with heart rate monitoring and provide some general guidelines for more effective use of heart rate.
The ability to use heart rate to monitor the intensity of a training session developed from the fact that there is a linear relationship between oxygen consumption and heart rate. While this is valuable information it has also lead to two problem areas. First, the relationship starts to break down at around 85% of VO2 max. Since many types of intervals and most speed work are done at or above this intensity heart rate alone cannot be used to monitor this type of work. Second, even though there is a relationship between exercise intensity and heart rate this relationship is different for different exercises i.e. heart rates for running will not be the same as heart rates for rowing for any given intensity (Figure 2). In fact, heart rates for erging and rowing are not the same. Some research indicates that heart rates on the water can be as much as 10 beats higher than on an ergometer for the same oxygen consumption. At the same time there is also evidence that in rowers who are on water year round their heart rates on water are lower than on the ergometer. This brings us to our first rule of heart rate monitoring. Heart rates are specific to the activity you are doing .
Heart rate is influenced by many variables. Duration of training, emotional stress, clothing, heat, dehydration, overtraining, loss of sleep, decreased blood volume, altitude, and detraining. During long duration steady state training sessions (60 minutes or more) the heat produced by the body has been shown to increase heart rate by as much as 20 beats/ minute. If you were to slow down to try to keep your heart rate the same you would change the training effect for the muscles. This leads us to heart rate rule number two: During steady state training speed or power output (intensity) should remain constant throughout the session regardless of increases in heart rate. Training in a hot environment can increase heart rate by up to 13 beats/min. This can make the accurate use of heart rate very difficult. Late in a training cycle heart rates can be very different than what they were a week earlier for the same power output. Whether this is higher or lower is difficult to predict. Emotional stress at work or the stress of exams at schools tends to increase heart rate during training. In addition, these types of stress decrease quality of sleep which further increases heart rate.
Rule number three: When training in hot weather or during periods of high stress use feelings of fatigue and comfort as a training guide rather than heart rate.
Heart rate is an individual response as is maximum heart rate. I have known people using exact same intensities who have had 20-30 beat differences in heart rates during the same training session. This isn’t necessarily due to differences in fitness rather it is something inherent to those people. Comparing heart rates to other people is unnecessary and often unwise. Training programs should not be based on general heart rate guidelines rather they should be based on individual responses. A training heart rate of 150 bpm may elicit very different adaptations for different people.
Rule 4: Don’t compare heart rates to others.
Because heart rate is an individual response and because it can be dependent on fitness level heart rate values need to be determined in relation to other physiological variables. There are three common physiological markers for aerobic training: Aerobic threshold, anaerobic threshold and VO2 max. Training programs are normally designed with the idea of changing these physiological points. In order to prescribe meaningful heart rate ranges these points have to be identified. This can be done through lactate testing or through an oxygen consumption test. The data is then plotted and meaningful heart rate ranges can be developed. If these points are not determined the heart rate prescriptions are purely guess work.
Rule 5: Heart rate ranges should be determined from other physiological data.
As mentioned earlier heart rate is not a good tool for monitoring intensity during speed work or interval training. Some coaches believe that heart rate should be used to monitor recovery between intervals so that fatigue levels can be controlled. While it is true that fatigue levels need to be controlled heart rate is not the way to do it. The fatigue during high intensity exercise is caused primarily by lactic acid accumulation. The time between intervals should be based on the time needed to reduce lactate levels. The relationship between heart rate recovery and lactate recovery is not very strong. In other words heart rate may have recovered but the lactate levels may still be too high to do the interval the way it should be done.
Heart rate is a tool for training. Like all tools it has limitation and should be used for a specific job at a specific time. Boat speed or power output on the ergometer are influenced by fewer factors than heart rate and may prove to be better indicators of training intensity. If you are going to use heart rate to monitor your intensity follow the guidelines outlined here and remember that heart rate is just a response to internal and external stimuli it should not be the main controlling factor for your training.
by Ed McNeely