Knowledge of which heart rate variables can help you to plan your training? Can a heart rate monitor help you decide whether you are over-training? How do you know if you are getting fitter? How can measuring heart rate variability (HRV) help you decide?
Disclaimer: I am not a trained sports medicine professional, and therefore the advice given here needs to be checked with your doctor or fitness professional before application. Values vary enormously from person-to-person and depend on your health, age, gender and fitness level. Sometimes a value which would be excellent for a very fit person can indicate a heart malfunction for someone who has a sedentary lifestyle.
As mentioned in the previous post, there are now a number of low cost, high quality smartphone (both Apple and Android) apps which allow you to very accurately measure, and store, many of the heart rate variables of interest to bushwalkers and other athletes.
Aerobic Capacity (VO2 max)
This is one of the most reliable measures of your cardiovascular fitness, and measures your body’s aerobic capacity ie ability to take up and use oxygen.
Some smartphone apps such as Polar Beat and many of the Polar wrist computers with OwnIndex® can estimate this with 86-93% accuracy by measuring your heart rate (255 beats) over 3-5 minutes, when you are lying flat at rest. The watch takes into account your resting heart rate and HR variability, along with body weight, height, and activity level. Care is needed in taking measurements in a consistent manner, usually as early in the morning as possible, before any activity, to allow day-to-day comparisons.
The improvement you may observe in as little as 4 weeks of aerobic training, is more important than the absolute value, and tells you whether your training program has been successful. I have used an F11 Polar wrist heart rate monitor for many years, and find that measurements taken every week give a very reliable indicator of my fitness trend.
You can download a copy of the Polar OwnIndex® chart, which gives you an indication of your level of fitness, based on age and gender.
Heart Rate Variability (HRV)
Overtraining is a major worry for those who train hard and often, as it may take many months to years to recover. Fortunately, overtraining can be predicted (controversial) by some high quality heart rate monitors and appropriate apps, which are able to sense small variations in resting heart rate and heart rate variability, the variation in the time difference between peaks, from day to day. In general, HRV decreases with overtraining and resting heart rate increases.
These apps (see previous post) can measure your HRV, in a few minutes prior to each day’s training, and advise whether you need a rest day for recovery, or whether you are making real progress. They are sensitive enough to be able to detect an approaching illness, changes in stress level, over-training and even variation in diet, if coupled with a high quality heart rate sensor (eg BlueTooth Polar H7); far more reliable and sensitive than the Tanita body composition scales I had been using until now to measure fitness trends.
These apps are widely used by athletes and professional sports people and have a lot of sports science research to back up their reliability claims. In the few days, since I have been measuring HRV, I have found these apps easy and quick to use and that they produce results consistent with my subjective assessment.
While trends on their own are useful, they are much more valuable if the trends can be correlated with changes in activity, diet, stress, training load etc. and several of these apps allow this “environmental” data to be logged simultaneously. Other apps such as Precision Pulse, allow training load to be calculated objectively, using the TRIMP method. Without an accurate measurement of your training load, a meaningful assessment of the trend is difficult.
Maximum Heart Rate (HRmax)
If you are using a heart rate monitor to adjust your training load then you need to know your maximum heart rate (HRmax), as it is essential measurement to determine your training zones. This can be estimated by a formula, but the actual value (as measured by a heart rate stress test) will vary in the range ± 20 bpm for most people.
Many smartphone apps use one of these formulae to calculate your HRmax, but usually offer the opportunity to enter a user value, if you have had it measured accurately.
During my training sessions of about 4 km, which include a 200m climb and a similar descent, my maximum heart rate reaches an average of about 82% of my HRmax (162 for myself) and my average heart rate is about 63% of HRmax.
Resting Heart Rate (HRrest)
This is usually measured after 15-20 minutes of lying down, before your day starts. If you are using a HRM, wait until it stabilises. The value depends upon fitness, stress, diet and health status, which varies on a daily basis. Very low HRrest may indicate a heart abnormality in someone who is not an athlete.
As you get fitter your resting heart rate should get lower. My average HRrest is 44, but varies daily between 40 and 49. An increase of more than few beats can indicate that your are over-training, but there are many other possible explanations, hence this measurement on its own has limited value.
Heart Recovery Rate (HRrec)
Heart rate recovery, a measure of the drop in heart rate when you stop exercising, is considered an excellent measure of fitness, with a more rapid drop indicating a higher level of fitness. After 30 minutes, your heart rate should have returned to its pre-exercise value, and if greater than 120 after 5 minutes, you have probably pushed yourself too hard. Walking slowly (cool down) for 5 minutes after stopping exercise is advised to increase recovery and reduce heart stress.
An alternative method involves taking your pulse during exercise and then again 1 minute after cessation. Divide the difference by 10 to get the Recovery Rate Number.
- Outstanding greater than 6
- Excellent 4-6
- Good 3-4
- Fair 2-3
- Poor less than 2
You should consult a doctor if it is 1.2 or lower, as there is a potential heart risk.
The recovery rate is independent of age, but is linked to fitness and heart mortality.
Orthostatic Heart Rate (OHR)
Your heart rate increases when you stand, and this increase is usually in the range 15-20 bpm. If it is greater than this you have probably not recovered from training the previous day, are under stress or have an illness approaching. This can be used as a rough guide to your fitness, as the lower this figure, the fitter your heart.
Measurements should be made after 15 minutes resting in a supine position (HRrest) and then again 15 seconds after standing, or alternatively just take the maximum reached after standing.
Alternatively, the difference between the your resting HR and standing HR can be recorded over a few weeks and the average used as a guide to decide the meaning of each day’s measurement and how to vary your training. My average difference (OHR) is 14 but varies widely between 6 and 31 depending on whether I have over-reached or have an illness approaching.
Heart Rate Training Zones
There are many apps and web sites that allow you to calculate your heart rate zones, if you know your resting pulse and maximum heart rate. If you don’t already know this, you can allow the app to estimate it from your age. Polar have a free app Polar Beat which can monitor your training while it is actually happening and store the results, but I prefer to use Walkmeter, as it gives excellent voice (Australian) feedback during the walk and can be controlled with the remote.
Typically 60-70% of HRmax is your fat burning and recovery zone, 70-80% is your aerobic zone, 80-90% is your anaerobic zone, and 90-100% is reserved for interval training. Depending on your reasons for training, it is important to keep within the correct zones, otherwise all your efforts can be wasted
One of the main limitations of this method is that heart rate varies depending on dehydration (+ 7.5%), heat and humidity (+10 bpm), altitude (+10-20%) and natural biological variation (± 2-4 bpm). BrianMac
Some more references
Bushwalking Fitness (14)
Training with iThlete
Maximum Heart Rate (BrianMAC)
Heat Rate Training Zones (BrianMAC)
More about the Polar Fitness Test
Heart rate training limitations
What Makes a Difference in Heart Rate Recovery Time After a Workout?
How Long After Working Out Does Your Heart Rate Return to Base?
This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.