Appropriate Use Of A Heart Monitor
Bringing back the “Good Ole’ Days”. Applying the old school art of “feel” in the modern training environment. Thankfully, there are a few old school, fundamental principles about cycling performance and training that never seem to loose their polish. For example, the importance of recovery is making a strong comeback. Much to the delight of many coaches, myself included. Another old school concept that is regaining popularity is developing the ability to make decisions about your workload based on accurate perceived exertion or “feel”. The simple art of monitoring the work you do on the bike by feel is experience a modern day renaissance.
For more than a decade, training programs have been dominated by the use of heart rate monitors to measure and monitor performance and exercise intensity. The technology has become very popular and has great value when use properly and for the right reasons. However, many riders have become too dependent on the readout on the receiver to estimate the intensity of their work. They have either forgotten or never learn how to feel what is happening to their body under the stresses of training and competition.
So much of your learning experience as an athlete is intuitive and the vast majority of your riding is driven by instinct. Both of these senses have great value when they are highly developed and used consistently. This on-the-job (bike) learning process comes naturally to cyclists and helps them develop a feel for what is going on and how to respond. In the course of your training and competition you need to learn to recognize the specific physiological responses your body has to different levels of exercise stress and adjust accordingly.
When monitoring HR during exercise it is important to understand that the heart muscle is passive in its relationship to the physical work you do. It does not drive the muscles to work. Rather, it responds to the work being done by your legs and other muscles by increasing blood flow to the working muscles as activity increases. The heart muscle only slows when the demand for oxygen decreases or fatigue sets into the working muscles decreasing the rate of work. This is why the focus of your attention should be on the muscles doing the work and not your heart muscle’s response.
Cardiac activity (heart function) is very sensitive to environmental and physiological changes. Factors like heat, cold, humidity, dehydration, fatigue, illness, stress and cardiac drift all effect HR as an accurate measure of the intensity of work being done. There are other physiological responses like respiration, muscle tension and lactate burn that, combined with HR, will give you a better picture of the stress on your body during exercise. During all training you should pay close attention to all these factors as they relate to HR, feel and perceived exertion.
All this being said, heart rate monitoring can very useful in a variety of moderate level training situations. For instance, if you are doing a particular workout that requires working in a narrow heart rate range for extended periods, say tempo training, you can set the monitor to the range desired and concentrate other aspects of the workout like pedaling mechanics, muscles tension and riding position.
The HRM is especially useful for limiting the intensity of training during prescribed recovery or endurance training workouts. Set the upper limit alarm to the desired ceiling heart rate and off you go. Your monitor is also useful for measuring the exercise stress during cross-training activities like swimming, XC skiing or circuit weight training when you body is working differently than during cycling and you want to ensure a quality session or make comparison between activities.
Monitoring During Competition?
I routinely tell my riders to leave their HRM in the car when they race. The only exception is ITT when we have been using HR to help establish a pace and schedule for the race. If we want to gather some HR data from an event I have the rider put the watch in their jersey pocket or turn it face down on their wrist and out of view. This way they will not be tempted to limit their effort by the HR data and can relax a race their bike and think about their strategy and tactics for the day.
Accounting for ‘Cardiac Drift’
Using heart rate to gauge intensity is made even more difficult by something called ‘cardiac drift’. Cardiac drift is the scientific explanation for the slow rise in HR during exercise relative to similar pace or workload, even for efforts that are at a constant pace like Tempo intervals. The magnitude of cardiac drift can range from 3-5 bpm for repeated short, hard efforts to as much as 20bpm during steady efforts like Tempo or TT intervals lasting 30 minutes and longer.
Cardiac drift happens for a variety of reasons having to do with conditioning, health, rate of fatigue, body heat regulation, hydration and environmental factors like heat and humidity. If you measure and adjust your workload using heart rate cardiac drift will cause you to ride slower and slower as the workout progresses. This is why it is so important to develop an accurate feel for your perceived effort and maintain a productive level of training.
Using Average HR to Measure Training Intensity and Overall Quality?
Average HR is a good way to monitor large blocks of training and increase the quality and goal orientation of your training. Let’s say that you are trying to increase your endurance and resistance to fatigue for road racing. You determine that your average race to lasts about 2 hours. Most of the time the racing is at and above your threshold and you want to be able to finish with the main field and eventually be able to land in and stay in the winning breakaway.
You can allocate time for race conditioning based on the estimated % of time during the race for different levels of intensity or pace. The largest block of your training would focus on increasing your power and speed at threshold. A smaller block would focus on effort above threshold and an even smaller percentage of training time would be dedicated to higher, sub maximal work. You would use average HR as a measure of the total volume of work done in these ranges to make sure you are covering all your conditioning needs and making progress toward your goal.
Example:
Lets say you have 15 hours per week for training. You will want to devote the largest portion (maybe 60%) of your time to increasing your capacity and endurance for threshold work. Since this type of work is best trained in longer segments (30-90 minutes) you will want to monitor the avg HR during the longer, steady pace efforts like tempo, threshold and TT intervals. Being certain that you are addressing this need you can move on to more specific training at higher levels based on a percentage of total volume for the week. During a training ride, once you have completed the required % of desired work for that session you can spend the rest of the time enjoying the ride without having to watch the readout on your HRM. This loosely structured approach will give you a lot of focus in the required areas without making you a slave to your HRM every minute of every ride.
Average HR and Training Balance
Another useful function of average HR is the distribution of work over several different ranges of performance to achieve balance in your training. This is useful for both recreational and competition athletes. Training stress needs to be varied to stimulate a cross section of positive adaptations that will benefit all areas of your development and performance. If you are going to keep track of avg HR during your training rides it is better to track the avg HR in 2-3 different training zones than for the entire ride. Regular time spent in active recovery, tempo, threshold and anaerobic areas ensures balance and will help you develop feel for each area.
Using VT (ventilatory threshold) Instead of HR
Every athlete has there own individual threshold capacity that is determined by things like age, conditioning, health and level of development. This threshold capacity, also known as MAC (maximal aerobic capacity), max aerobic power and functional capacity is very closely related to a physiological response known as ventilatory threshold (VT). This onset of blood lactate accumulation (threshold, MAC) correlates to the high levels of Co2 (carbon dioxide) production resulting from maximal aerobic energy metabolism.
These high levels of Co2 in the blood trigger a rapid increase in respiration that is very noticeable for every athlete. If you learn to recognize your VT you will be able to make better decisions about continuing than if you are using HR alone as your gauge. It is important that you learn to identify the feeling in your legs and other physiological responses associated with VT in your training.
There are many workouts like Vo2 max intervals that can be done using only VT as the measure of exercise intensity. Typically, Vo2 intervals range from 3-4 minutes at intensity about 5%-10% above MAC. All you have to do is settle into a manageable pace above VT for the duration of the intervals and you will be accomplishing Vo2 max level training.
Remember, your HRM is a device that collects data from only one source. A training program with a balanced focus on progress and development should be dependent on information and data from many different sources. Your heart rate monitor alone cannot tell you with any certainty if your legs or other muscles and systems are working at the desired or optimal levels. Once you learn the different signs of increased exercise stress and come to trust them you will be able to train and compete more effectively.