Have you heard other runners mention working to their heart rate, or seen them wearing a heart-rate monitor (HRM) and wondered what the fuss is about? Or, wondered whether training to your heart rate could improve your running and, if so, how to give it a go yourself?
Dr Charlie Pedlar is a physiologist at the St Mary’s Clinic, St Mary’s University (smuc.ac.uk), a performance and rehabilitation centre for athletes – professional or amateur. “Your heart rate (the number of heart beats occurring each minute) is an excellent measure of the overall stress your body is under,” he says. It shows the physiological (and sometimes psychological) ‘load’ your body is dealing with. “Not only this, it can be used to objectively set your training intensity and monitor your gains in fitness,” he adds. As you get fitter your heart, which is a muscle, adapts, gets larger and more efficient – it can then eject more blood into your circulation for each heartbeat, resulting in a lower heart rate.
Runners draw on the aerobic and anaerobic systems. Slow running is predominantly aerobic, and fat and carbohydrates produce the energy we need to run. As the intensity increases we use our anaerobic system, and rely more on carbohydrate. The deeper you get into anaerobic running the more limited your performance is. “Training allows you to run faster and remain in the more efficient aerobic zone,” says Dr Pedlar, “and training plans include running at different intensities, using the transition (or threshold) between aerobic and anaerobic exercise as a key reference point. Terminology such as ‘steady’, ‘threshold’, ‘tempo’ and ‘interval’ running may be used to describe training zones. Each zone has subtly different training effects.”
You can use any number of heart-rate zones, and different coaches will favour different approaches to this. Most commonly, though, runners use five heart rate zones, split into 10% zones, which all have different training benefits. For example, for a steady recovery run after a hard session, or race, you should aim for your heart rate to stay between 50-60% of your maximum heart rate. If you are doing short, fast intervals, to improve your leg turnover and speed endurance, aim for 80%. And don’t forget, your breathing can also help you estimate your training zones. Below threshold conversation is easy; at and above threshold you should only be able to give one-word answers. For intervals, expect heavy breathing and no conversation.
First you need to find your resting heart rate, as well as your maximum heart rate with a heart-rate monitor. “Resting heart rate is best measured before you get out of bed in the morning, by measuring your pulse for 30 seconds (and multiplying by two),” says John Brewer, a professor of applied sport science at St Mary’s University. Do this for four days, then work out the average value. If you find that your daily value then rises above the average for a couple of days or more, it could suggest that you are tired or have a minor illness. “This should be seen as a signal to reduce the quantity and intensity of your training,” says Professor Brewer.
Maximum heart rate decreases with age; a simple way of calculating it is to subtract your age from 220. This method can be inaccurate but it gives you a rough figure to work towards. Most people find that training at an intensity of between 60% and 80% of maximum heart rate works best. However, heart rate does gradually increase during a run, even when the run is at a constant pace. “Make sure you don’t set off at the top end of the range otherwise you will soon find the session too demanding,” suggests Professor Brewer.
Heart-rate data can provide a valuable means of measuring improvements in your cardiovascular fitness, and guide you to be able to work harder, and get faster. “Lower heart rates at given speeds are indicative of improved fitness. Similarly, reductions in resting heart rate can also indicate improved cardiovascular efficiency,” says Jack Wilson, a sports scientist at Porsche.“Repeating key training sessions each month whereby you run at a fixed speed for at least 20 minutes over a set route are useful,” he says. Recording your average heart rates during these sessions – and while you are resting – allows you to evaluate changes in heart rate over time.
A few words of warning: running in hot conditions, dehydration and caffeinated drinks can cause your heart rate to elevate above normal. Be aware that these factors may affect your heart rate before you start training. It may be worth consulting your doctor before engaging in strenuous exercise.
And remember, there is no correct training recipe to tell you how much of each kind, or zone, of running is optimal. However, science has shown that repeatedly including various intensities of training gives greater gains than either plodding along at the same speed, or thrashing out your miles as fast as possible. “Just as important, don’t become a slave to your heart-rate monitor,” says Professor Brewer. “Rather, use heart-rate training to get a ‘feel’ for the intensity you should train at, and rely on feedback from your body, not just your HRM.”