The Heart Rate Monitor

If you want to get the most health and fitness benefits from your training, a heart rate monitor is an essential training tool. If used properly, it will enable you to achieve maximum fitness levels while avoiding illness and injury caused by overtraining. However, a heart rate monitor is useless if you don't know how to use it. Many athletes have little idea what the numbers they see on the monitor actually mean. Some athletes wear the monitor and pay little attention to it while other's become a slave to the monitor and ignore other important feedback from their body. A heart rate monitor used properly while training is a great tool to find out what is going on in side you. Your heart rate does not lie and with the aid of a heart rate monitor you can tell exactly how your system is responding to your training session. A heart rate monitor helps take the guesswork out of your training in comparison to only using perceived effort to gauge your training.

Should you always follow your heart rate monitor and ignore how you are feeling during a workout? NO. The use of a heart rate monitor is best used in conjunction with other feedback such as perceived effort or exertion. Dr. Gunnar Borg developed a scale in the early 70's to determine perceived exertion. The scale ranges from 7 to 20 with the lower number being a very, very light effort and 20 being a maximum effort. Your Anaerobic Threshold is usually some where between 16 and 18 at a hard to very hard effort. The day after a hard training session you may find that the pace of an easy aerobic training session may feel harder and performed slower than normal while your heart rate is extremely low. Do you work even harder and try to get your heart rate up or do you listen to your body and slow down even more realizing that the hard session the day before took more out of you than you realize? In this case it would be best to listen to how you feel rather than only watching your heart rate monitor.

Heart Rate Training Zones

Now that you've finally purchased one and read through the owner's manual, how do you use it properly to help you train more efficiently and smarter to get you to the podium at your next race versus seeing it as a cool new toy that's novelty eventually wears off and eventually ends up collecting dust? To train correctly with your monitor it is essential to set up proper training zones. Each and every person's training zones are very individual and need to be determined before using a heart rate monitor to effectively help you while training. There are several formulas out there such as 220 minus your age to determine your Maximum heart rate. Many people use this formula to calculate their training zones. This and several other formulas using age, resting heart rate, and your current level of fitness are predictions and will only work with a small majority of people. It might work 50% of the time but if you're off by as little as 5 beats the results could be disastrous. It is best to determine your training heart rate zones without the use of a generic formula. The most accurate way to determine heart rate zones is to have a lactate test performed at a qualified test site to determine your aerobic and anaerobic thresholds. Shown below is an example of training zones produced following a run lactate test at Dynamic Health Services:

Anaerobic Threshold (AT) is specific to each individual, but is trainable. In general, your AT is the point at which enough anaerobic metabolism occurs such that more lactic acid is produced than can be rapidly cleared from the body. You know this level as that point where breathing becomes labored but maintainable. If you continue beyond this pace or for an extended period of time, you soon will reach failure and will have to slow the pace in order to continue. We've all had this happen in a race when everything seemed so easy at the beginning but we got progressively slower at the same level of perceived exertion later in the race. This usually occurs anywhere from 65-95% of ones maximum heart rate depending on your fitness level. Thus, it is impossible to use any generic formula to determine your training zone. Furthermore, your AT will be different from sport to sport so your training zones will be different as well. On average, in relation to triathlon, your running AT will be higher than your bike AT and your bike AT will be higher than while swimming. The differences will be dependant upon which sport you have more experience in.

Factors Affecting Heart Rate

Once you have determined your proper training zones, it is important to gain an understanding on how outside factors might affect your heart rate readings. Following is a brief discussion on some of the factors affecting heart-rate and the recommendations on how to adjust your training/racing accordingly.

As stated earlier, it's important not to become a slave to your monitor but rather use it as a tool to guide overall training. For example, if you are going for an easy run and feeling good but your monitor reads 170 bpm and your easy run should be done at 130 bpm, do you stop? In this case, it is likely that you are receiving interference from an outside source. Check that you are not near other people that have heart rate monitors, high voltage power lines, televisions, mobile phones or other sources of electromagnetic disturbance. In most cases, you will receive a proper reading once you are away from the source of interference.

"Cardiac drift" is a second factor that may affect your HR readings. After prolonged exercise at moderate intensities in a normal or warm environment, heart-rate will often rise despite no felt increase in intensity. This is called "cardiac drift" and can produce heart-rates up to 20 beats per minute higher than early session heart-rates. The cause is core temperature increase. Here heart-rate does not offer a true reflection of intensity so in this case heart-rate is best used in conjunction with power (on the bike) or pace (on the run) and/ or perceived exertion. The remedy is to start at the lower end of your training zone and over the course of the session realize that the heart-rate will rise up through and slightly above the upper heart-rate limit while holding constant intensity.

In cold weather, the opposite may hold true and there may be an increase in oxygen uptake with heart-rates staying similar to those of normal conditions. In this case, the body is working harder but this is not shown in the readings on your monitor. Here heart-rate underestimates the intensity. Thus, you should train in the lower portion of the prescribed training zones. Hot weather gives much higher heart-rates than usual. This is due to the core temperature increase as discussed in cardiac drift plus the increase in environmental temperature. Increases of between 10 and 30 bpm have been reported in the heat, with no change in actual intensity (watts/ speed). Here again, heart-rate is not reflecting the true intensity. In this case, the bpm's shown over estimate the workload. However, the higher heart-rate is indicative of a higher total body stress as the body works harder to cool and maintain homeostasis. Even though the intensity of a work bout in the heat is not as high as in normal weather, the stress the body is under is increased. Therefore, train at the normal prescribed heart-rates (which will mean an easing off in power and pace) and use the heart-rate as a guide of total body stress.

Nutrition and caloric intake is another factor that may affect HR readings and is important factor to consider, especially for the long distance athletes. During racing, a lowering of the heart-rate in conjunction with an increase in the perceived effort may mean that you need to take in calories. In this case, the heart-rate monitor serves as your blood sugar level monitor and saves you from the much dreaded "bonk". If you find that your heart-rate won't rise to normal levels early on during training sessions, it may be a sign of underlying fatigue from overtraining, especially if your legs feel heavy, or impending illness. Here you have two choices. Either back off the pace and do a shorter active recovery session or head home for passive recovery. Dehydration is another common occurrence, especially, but not solely in the heat and leads to the opposite results of poor caloric intake. Here the blood plasma volume drops so heart-rate must increase to deliver the same amount of oxygen as cardiac output rises. The bpm rise may be between 2 and 7% (that's up to 160 bpm from 150 bpm). The remedy here is obviously to drink, but also to use heart-rate as a guide of "total body stress".

Body positioning may also affect your HR. If you are a cyclist, you may find that as you strive to make your time-trial position more aerodynamic that your heart-rate at a given intensity has risen. Many think that this means that the new lower position is counter-productive. This is not necessarily so. Research shows that both oxygen uptake and heart-rate are higher in the "aero" position than the standard road position. This is attributed to the increased contribution of the shoulder muscles and a less efficient hip angle. The costs in heart-rate are considered negligible compared to the time savings of improved aerodynamics. Although the heart-rate may be up by 2-5 bpm, it is not a true reflection on intensity so you can allow your heart-rate this "drift" when on the aero-bars, knowing that there has been no real increase in effort. The key here is to train in your aero position and be aware of how it affects you. As long as you can maintain an efficient pedal stroke and cadence and as long as your breathing mechanics are not compromised, the aero position is the way to go for faster times despite the small bpm increase. If you are a triathlete, you may also find that your heart-rate is elevated early on during the bike ride after going from a horizontal position during the swim to upright running then transitioning to the bike. The key here is to train for this transition and to wait until you are some time ( might be 30mins+) in to your race to let your heart-rate settle down and give you more honest readings.

On race day, you may find that your heart-rate is up at high levels even when you are warming up. Here the heart-rate is exaggerating the intensity and the adrenalin coursing through your veins is responsible. Furthermore, it has been shown that athletes can achieve higher heart-rates during race situations than during training sessions even though the intensity, power or speed produced has remained the same. These race day heartrates again over-estimate the intensity. In all these cases, perceived exertion is a useful tool to use in conjunction with your heart-rate. For short races (under 1 hour), it may be better to forget your HRM completely unless you are recording the bpm to analyze later. For longer races, the HRM has many benefits listed throughout this discussion. In racing conditions, often it is your gut instinct that will tell you hard you should go with your HRM providing back-up information and real-time data on the current stresses and conditions you are facing.

The most important message for you to take away from here is that, HRM's are a great tool but they are best used in conjunction with other information. Heat, dehydration, bike position, biomechanics and day to day general health, nutrition, and stress all affect the numbers you see and some of these affect the intensity you feel. Taking into account all the factors allows you to further maximize your training and take your performance to even higher levels.

Source: www.cuttingedgeworldwide.com

Next Lactate Testing Article: Sample Run Results

Return to Dynamic Health Services Lactate Testing Page