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Using Heart Rate Training Zones Effectively
By Dr Grant Wilkinson D.C, B.Sc, M.Sc *
Heart rate training is used the world over by elite and amateur athletes alike and for good reason! The body will only adapt and grow fitter to sufficient of overload or stress. But too much stress and you risk over training and burnout.
To be efficient endurance training must reflect the demands of the sport or event. For most athletes, heart rate training offers the most practical way to elicit the right training intensity however it must be remembered that this method of training also has its disadvantages and flaws.
Heart rate training zones are based on maximum heart rate. And it's here where the major problem lies. Most of us of heard of the classic "220-age" formula. For those who haven't - deducting your age from 220 is said to give a “theoretical” maximum heart rate. The trouble is that for a significant number of people its way off - maybe by as much as 25 beats per minute.
Heart Rate Training Zones
Different exercise intensities tax the body's energy systems in different ways. Exercising at 60% of maximum heart rate (MHR) for example predominantly taxes the aerobic system in most people. If exercise duration is long enough the major source of fuel is fat. This type of intensity is often favoured by people who want to lose weight and are generally de-conditioned.
A heart rate training zone of 70-80% maximum will still predominantly tax the aerobic system in fitter individuals but the main source of fuel will be glycogen. This is the heart rate training zone that endurance athletes should aim for. Using the theoretical formula for MHR we can use an example to calculate a target heart rate:
Jason is 35 years old and wants to do a 10km run:
Maximum heart rate (MHR) = 185bpm (220-35)
Target heart rate zone = 70-80%
Lower target heart rate (70%) = 130bpm (185 x 0.7)
Upper target heart rate (80%) = 148bpm (185 x 0.8)
Make This More Accurate!
Simply using 220-age makes no allowances for individual differences as all 35 year olds will have the same heart rate training zones. The “Karvonen” formula tries to make this more accurate as it takes into account the resting heart rate of a person and as such makes it a little more specific. Because resting heart rate (RHR) decreases with conditioning it also makes allowances for differing degrees of fitness.
Keeping with our example above here's how Jason (RHR = 65bpm) would use the Karvonen formula to achieve a more accurate heart rate training range:
Karvonen formula: MHR – RHR x heart rate zone + resting heart rate
Lower target heart rate (70%):
- 185 - 65 = 120bpm (this is called the 'working heart rate)
- 120 x 0.7 = 84bpm
- 84 + 65 = 149bpm (lower limit)
- 185 - 65 = 120bpm (this is called the 'working heart rate)
- 120 x 0.8 = 96bpm
- 96 + 65 = 161bpm (upper limit)
As you can see, the Karvonen formula calculates a higher training zone than just using 220-age which is the case with most athletes. As you begin to exercise in your heart rate training zone, you may want to stick to the lower level to start off.
It must be noted that depending on the discipline, your MHR will change. Take swimming for example, the MHR when swimming tends to be lower than for running events. To adjust for this subtract 13 from your maximum heart rate (i.e. use 207-age rather than 220 - age.)
Anaerobic Threshold and Heart Rate
In previous articles we have examined and explained the terms ‘lactate’ and ‘anaerobic threshold.’ For our purposes we'll keep things simple and define anaerobic threshold as the point at which you begin to accumulate lactic acid.
Before this point your body is able to remove lactic acid as quickly as it is produced - hence no accumulation. As soon as you reach exercise intensity over and above your anaerobic threshold, lactic acid begins to accumulate and within a short space of time your body will be forced to slow down. The key now is to find what your anaerobic threshold is so you can use it in training.
Anaerobic Threshold: The Conconi Test
The simplest way is to assume it occurs at 85-90% of your MHR and you can simply train at that intensity in short bursts to help improve it. An alternative is to use Conconi's test. This test too has its disadvantages and flaws and so is used best as a rough guide more than a definitive test. Theoretically the heart rate plateaus briefly before rising sharply again this is said to correspond with anaerobic threshold.
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You can do the Conconi test using a treadmill, heart rate monitor and an assistant. Begin by warming up at a light pace for 5 to 10 minutes. Set the treadmill to a 1% incline. The run should last between 2.5km and 4km to allow sufficient data to be collected. The speed is gradually increased every 200m by 0.5km/hr and as a guide 8 - 10 km/hr is a good starting point. Record the heart rate and speed at each 200m interval and continue until exhaustion, then complete a 10 minute cool down.
You can now plot a simple graph like this one to read off your anaerobic threshold. You can see from this graph the obvious plateau and deflection in heart rate. It seems to correspond with an approximate HR of 172bpm. As mentioned, there is debate surrounding the accuracy of this test and it seems to work best when there is an obvious visible deflection in the graph. If you start looking for a plateau, accuracy begins to diminish.
Heart Rate Training to Increase Anaerobic Threshold
Here's a simple program example of how you can use heart rate training to increase your anaerobic threshold. Using the example in the graph, we will assume your HR at anaerobic threshold is 172bpm. Start by completing two 6-10 minute runs at 5% below your anaerobic threshold target heart rate. In this case it's 163bpm (i.e. 172bpm x 0.95% = 163bpm). Rest for 2-3 minutes between runs and do this twice a week.
Gradually build up the length of each run or the number of repetitions (up to 6). Also increase your target heart rate up to your threshold. The target eventually is to reach a sustained, 20 minute run at or just above your threshold heart rate. Make sure you always complete a thorough cool down at the end of each session and it is best to re-test your anaerobic threshold every 6-8 weeks and record results to see whether you are improving.
