Many runners focus on speed. The main target is to get faster, right?
I used to think like this, always hopeful on each training run that my kilometre time would be a few seconds less than before. But as you get older speed becomes more difficult. It was only when I heard about the different ATP cycles that I realised there was something better to track during training. That is heart rate.
As you exercise your heart rate increases. Some exercise prompts a greater increased HR more than others. Running soon moves me up the zones to zone 5, whereas on the rowing machine this is hard to reach.
There is no specific processes in the body that depend directly on the heart rate. The value however is a useful proxy for ‘effort’ or ‘intensity’. So a higher heart-rate becomes an indicator of a higher work rate.
Your running watch uses your age to allocate heart rate zones.
Convention says that the maximum heart rate for a person is 220 less their age in years. So a 70 year old will be allocated a maximum hear-rate of 150 beats per minute (bpm); a 50 year-old a maximum of 170 bpm. The minimum heart-rate is typically between 50 and 80 bpm, this is measured by the watch when you are resting.
To arrive at your personal heart rate zones that range between minimum and maximum is simply divided into 5 equal divisions. So for if the range is between 70 and 150, zone 1 is 70-86 bpm, zone 2 is 87-102, zone 3 is 103-118, zone 4 is 119-134, and zone 5 is 135-150.
The zones are given some description which equates them to the type or effect of the exercise at that rate. Of course the body’s response to exercise does vary from day to day and so the zones and the associated effects are not hard and fast, but provide a useful guide.
My watch names the different zones 1. warm-up; 2. easy; 3. aerobic; 4. threshold; and 5. maximum.
There are a couple of noticeable metabolic changes that relate to intensity of exercise. These provide for a more targeted way of allocating zones for use in training.
The Aerobic Threshold is the point where is becomes difficult to maintain a conversation and breath through the nose. This is typically assigned to the top of zone 2.
The Lactate Threshold is the point at which the level of lactic acid in the muscles is increasing faster than it it is removed. This is typically at the divide between zone 3 and zone 4.
Most running will be at a heart rate above the aerobic threshold, otherwise it doesn’t really feel like training. Productive training below the lactate threshold results in improved endurance. This means an increase in capacity to run for a long time.
If the heart rate goes over the lactate threshold it is considered ‘anaerobic’ training and a different metabolic process is invoked. Productive training at this level is associated with increased speed.
Training – in practice
So the main display on my watch is set to heart rate.
I constrain most runs by heart rate. For example early in the training cycle I keep the rate below 125. In theory it is possible to manage just by running slower and easier. But this is not straight forward, and in practice it means a stop-start style of running. I try to keep the rate constant, but inevitably it goes above 125. As it heads toward 130 I start walking; the rate drops, and when it is below 120 or 115 I start running again.
Later in the season I might work with a constraint at 135 – starting to walk at about 137 or so, and beginning to run again when the rate goes below 125.
Depending on the base level of fitness, this process works well for runs up to an hour or so in duration.
For races and public timed runs I still have the heart rate on the display – but not necessarily for constraint purposes. Here it provides a proxy for effort and output. Sometimes it can advise me to reign back a bit – for example a rate of 155 or so early on in a long race will be at a pace that I know will be unsustainable. Fatigue would become a problem in the second half of a 10 or 20-miler. For a 5k parkrun, probably it won’t matter, even if I have to reduce the pace before the end there will be no significant physical penalty. These parameters all depend on relative fitness and experience of course.
Having a timer as the main display on a watch will not provide many clues about your physical condition!