To work out your training intensities, I believe that the Karvonen method is the best. It relies on your own maximal heart rate and lowest resting heart rate to define intensities. This is all outlined in my book, Healthy Intelligent Training, however we’ll go over this again in brief.
Finding your maximal Heart Rate:
You need to be relatively well-rested and ‘fresh’ before you attempt a maximal heart rate test, and in good shape generally. You won’t get any sense out of a test done when you’re not reasonably fit in the first place. You can find your maximal heart rate, after a good warmup, by, let’s say, running for at least three minutes hard up an incline, and seeing where the HR hits maximum. Most recent heart rate monitors have a mode where HR can be ‘sampled’ every few seconds. Otherwise just note your pulse every few seconds as you get near the end of your three minutes.
For people training for distances 15km or longer, there is very little need to spend much time at intensities above VO2 max. It will ‘detrain’ your aerobic system somewhat.
Establish Your Resting Heart Rate:
This can be said to be the average of your waking heart rate three mornings in a row, when you’re not in hard training. Wait a few minutes after getting up before you relax and take your morning heart rate. The heart rate can tend to zoom up a bit on first awakening, so just have a bit of easy moving around for several minutes to let things settle down.
The Karvonen Method: Establishing Your Heart Rate Reserve
To work out this figure, use the following formula: HRR= (max HR–resting HR).
For someone with a maximum HR of 195, and a resting HR of 45, the HRR will be 150.
The lowest useful aerobic zone in this example, for gently increasing total capacity, will be [60% x (150)] + [resting HR], or (90 + 45), or 135 beats/minute. Any lower than this is really only for aerobic recovery or restoration of normal blood pH (the acid/alkali balance; perfect health has a pH of about 7.4);
The really useful aerobic zones start around 60% of HRR, which coincides with a lactate concentration of about 2mmol/litre. This is also known as the aerobic threshold.
Work out your rates for 65%, 70%, 75%, 80%, 85%, 90%, etc. These then can be entered into your diary and you can see what zones you venture into when you’re running over varying terrain, (the HR will go up on up-hills, and decrease on descents) and set an alarm at an upper limit if the purpose of your run is basic aerobic bread and butter endurance.
% HRR HR
The table below shows the pulse rate expected at each intensity in the previous example. The best heart rate for the weekly or bi- weekly “3/4 effort” run would be between 75% and 80% of maximum HRR:
in this case it’s an HR between 158 and 165, which is a full 8-15 beats lower than a typical threshold zone, which would hover around an HR of 173. In the case of this “marathon intensity” run, you can see that the“3/4 effort” is equivalent to 75% of maximum HRR.
Initially on long efforts designed to be ‘aerobic’, this athlete should hover along at HR’s between 135 and 143, which equates with Lydiard’s ‘1/4 effort’ intensity. Most athletes will be running on fat fuels rather than glucose/glycogen (stored glucose) at lower intensities, especially if they train aerobically over longer distances regularly.The breaking down of fats to provide energy is called lipolysis, or lipo (lipid/fat)–lysis (breakdown).By the same process, the breakdown of glucose, or its stored starch, glycogen, is known as glycolysis. The major problem for marathoners or endurance athletes who race for just over 2 hours is that most athletes can’t store enough glycogen to maintain very high percentages of their oxygen uptake for much past 2 hours, no matter what they do. This point of rapidly running out of energy is known as bonking or hitting the wall. However, the steady long aerobic running without resorting to carbohydrate snacks or gels will force the body’s fat metabolism to adapt, and polish up its ability to break down fats for energy. The diagram below shows just how much the fuel mix at varying running intensities can change with fatty-acid metabolism adaptation.
As you’ll see from the diagram above, based on David Costill’s research, a runner who trains aerobically at moderate levels of intensity will become much more efficient at preferentially breaking down fats for energy. In this example based on hard data, the athlete initially runs on a fuel blend of 50% fat/50% carbohydrate (glucose or glycogen) when at 100% of his or her untrained aerobic capacity. After several years, the athlete will find himself running aerobically on 80% fat fuels/20% carbohydrate, at paces that were formerly right at the maximum of their aerobic capacity, but what is now a steady-state 80% of their newly developed aerobic capacity. The newly trained maximal aerobic output is now achieved almost entirely on fat fuels, as long as the athlete hovers along at 80% intensity or less. 80% of maximal aerobic capacity represents a good level of performance, but it’s just not quite fast enough to run very fast times without rapidly depleting the remaing carbohydrate fuel.This adaptation to fatty acid metabolism was the desired response to Arthur Lydiard’s long distance training, however when athletes raced the marathon they still had the hurdle of restricted glycogen storage as a limiting factor. We’ll deal with a very sound, recently proven nutritional way to make sure that the experience of bonking/blowing up/hitting the wall in competition or training never happens to you, in an upcoming post.
Just so you know that the theoretical model illustrated above is based on real people like you and me, I’ll share a graph sent to me a few years ago by René Borg, now a Lydiard-based athletics coach, from Dublin. You’ll see his true aerobic capacity (in green) improving each year, with the anaerobic capacity (in blue) staying largely unchanged.
As you get fitter aerobically, your comfortable cruising speeds will increase, and, for any given heart rate, more distance can be covered.
You may well be able to run longer and faster in complete comfort than it was possible to run at maximally some weeks earlier.
Why? Because steady-state, comfortable aerobic training for long periods is known to
- Greatly enhance capillary density
- Greatly enhance mitochondrial activity
- Greatly enhance aerobic enzyme pathways
- Greatly enhance breakdown of fatty acids for muscle fuel (lipolytic beta–oxidation)
- Enhance the capacity and pumping power of the heart chambers (ventricles-especially the left).
These all coalesce into a scenario where you can run a long way, faster than previously, using less carbohydrate and far more fat for fuel.
How much hard training is involved? None. But you’ll have to set aside sufficient time to do the necessary volume of work every day. Varied scenic routes and terrains will help alleviate any feeling of boredom.