Use of heart rate monitors by endurance athletes: Lessons from Triathletes
Monitoring our heart’s physiological response to changes in exercise intensity during physical activity – that’s a fancy way of saying your heart rate going up & down – can be used as an effective tool in hitting athletic performance targets.
Now some triathletes/cyclists/runners might be reading this & thinking ‘I have seen all this before, just another gimmick’; so before I start stressing the real science behind it, I want to take this heart rate monitor story from Mark Allen, only the second six-time Ironman Triathon World Champion:
“I came from a swimming background, which in the 70’s and 80’s when I competed was a sport that lived by the “No Pain, No Gain” motto. My coach would give us workouts that were designed to push us to our limit every single day. I would go home dead, sleep as much as I could, then come back the next day for another round of punishing interval sets…… Every run, even the slow ones, for at least one mile, I would try to get close to 5 minute pace. And it worked…sort of. I had some good races the first year or two, but I also suffered from minor injuries and was always feeling one run away from being too burned out to want to continue with my training.
Then came the heart rate monitor. A man named Phil Maffetone, who had done a lot of research with the monitors, contacted me. He had me try one out according to a very specific protocol. Phil said that I was doing too much anaerobic training, too much speed work, too many high end/high heart rate sessions. I was forcing my body into a chemistry that only burns carbohydrates for fuel by elevating my heart rate so high each time I went out and ran.So he told me to go to the track, strap on the heart rate monitor, and keep my heart rate below 155 beats per minute. Maffetone told me that below this number that my body would be able to take in enough oxygen to burn fat as the main source of fuel for my muscle to move. I was going to develop my aerobic/fat burning system.
What I discovered was a shock.
To keep my heart rate below 155 beats/minute, I had to slow my pace down to an 8:15 mile. That’s three minutes/mile SLOWER than I had been trying to hit in every single workout I did! My body just couldn’t utilize fat for fuel.
So, for the next four months, I did exclusively aerobic training keeping my heart rate at or below my maximum aerobic heart rate, using the monitor every single workout. And at the end of that period, my pace at the same heart rate of 155 beats/minute had improved by over a minute. And after nearly a year of doing mostly aerobic training, which by the way was much more comfortable and less taxing than the anaerobic style that I was used to, my pace at 155 beats/minute had improved to a blistering 5:20 mile.
That means that I was now able to burn fat for fuel efficiently enough to hold a pace that a year before was redlining my effort at a maximum heart rate of about 190. I had become an aerobic machine! On top of the speed benefit at lower heart rates, I was no longer feeling like I was ready for an injury the next run I went on, and I was feeling fresh after my workouts instead of being totally wasted from them”
If an athlete wants to train smart rather than just to work out, using a heart rate monitor to zone in on the right intensity can help improve not only your stamina but make you an ‘aerobic machine!’. Quantifying your training using your heart rate makes it possible to plan a course of action based on the outcomes from your training intensity, i.e. a heart rate monitor helps you gain an accurate picture of workout intensity.
Pacing Strategies – Whats the science on why you should adopt a heart rate monitor
It is widely recognized that an athlete’s ‘pacing strategy’ can have a significant impact on performance and thus using
a heart monitor in competition can drastically improve race times. Sports science studies tend to suggest that well trained athletes usually adopt a positive pacing strategy – whereby after peak speed is reached the competitor progressively slows. This has been examined by neuroscientists in sport – ‘The role of information processing between the brain and peripheral physiological systems in pacing and perception of effort‘; it seems that the most important factor in allowing the establishment of a pacing strategy is knowledge of the endpoint of a particular event – a similar mechanism even at different distances or event duration.
In a 2007 paper on Distribution of power output during cycling: impact and mechanisms, the neuro-mechanism for pacing was summarized as follows:
“The pacing strategy ‘algorithm’ is sited in the brain and would need afferent input from interoceptors, such as heart rate and respiratory rate, as well as exteroceptors providing information on local environmental conditions. Such inputs have been shown to induce activity in the thalamus, hypothalamus and the parietal somatosensory cortex. Knowledge of time, modulated by the cerebellum, basal ganglia and primary somatosensory cortex, would also input to the pacing algorithm as would information stored in memory about previous similar exercise bouts.”
It seems even for experienced cyclists there is a naturally selection of supraoptimal (greater than optimal) work rate at the start of a longer individual time trial, even though the selection & distribution of work rate is one of the many factors that influence cycling speed – and whether such as start can be ‘blunted’ through coaching or the monitoring of psychophysiological variables is unknown.
If we examine the running phase, the evidence – from ‘Pacing strategy during the initial phase of the run in triathlon: influence on overall performance‘ which compared highly trained athletes’ efforts in a self-paced 10km & a triathlon – points to a noticeable overall time benefit [particularly in the final kilometres] if the pace is 5% slower than their 10km control running speed. Crucially improvement in the cycle-to-run transition demonstrates a large gain in running leg results – for all those brick workout enthusiasts. This demonstrates that triathlon performance is directly related to pacing strategies
Longitudinal monitoring of power output and heart rate profiles in elite cyclists has shownn that better performances are characterized by lower variability in power output – i.e. keeping pace consistent – and higher intensities during intervals.
For cycling, speed is not an accurate indicator of exercise intensity (or power) – cross winds, different gradients – and therefore alternatives have to be found to monitor exercise performance. Power output is one indicator [as illustrated] – but crank power meters are expensive presently & again differ in terrain profiles – however heart rate monitors are incredibly accessible & easy to use, such as the MIO Alpha heart rate sports watch.
Of course this is supported by cardiovascular experts such as Sally Edwards of Sacramento, California, author of The Heart Rate Monitor Guidebook to Heart Zone Training (Heart Zones Publishing 2010), “You only need two pieces of gear to work out: a good pair of athletic shoes and a heart rate monitor.”
From studying a review on the use of heart rates in triathletes there are several points for athletes wishing to have the optimal use of their heart rate monitors in training & racing:
1). Formal maximal exercise tests should be performed to determine true HR max in each exercise mode
2). Athletes should expect their heart rates to decrease over the course of a long race. No doubt this includes an Ironman; where over a prolonged period of exercise (>6hours) a highly trained athlete may expect to follow an average intensity close to 80% HRmax but should expect intensity to decline 6-7%. The change in heart rate over a given intensity is known as ‘Cardiac drift’; and as described by Jeukendrup & VanDiemen in ‘Heart rate monitoring during training and competition in cyclists’ does not only occur because of exercise duration but especially in hot environments or at altitude.
3). Athletes should not assume they will have completely recovered from a strenuous workout if submaximal exercise heart rates are unchanged.
Pacing strategies at ultra endurance events
Investigators have found that the optimal marathon time/overall ultra-endurance event time for an ultra-triathlete was when the exercise intensity was set at near the first ventilatory threshold (VT1, a marker of intensity that can be heard in a person’s breathing at a point where lactate begins to accumulate in the blood. A person who is at VT1 can no longer talk comfortably while exercising). To determine the VT1, triathletes [in this study for example] perform progressive exercise tests of cycle ergometry & treadmill running; and as described by Cottin et al in 2006 Assessment of ventilatory thresholds from heart rate variability in well-trained subjects during cycling; ventilatory thresholds can be assessed accurately using heart rate variability (HRV) analysis.
Of course sports scientists reading this may point out that the ‘coincidence between the ventilatory thresholds & those thresholds using the lactate response does not happen all of the time, suggesting that there is no relationship between the cause-effect between these phenomena’ – as quoted from ‘Comparison between anaerobic threshold determined by ventilatory variables & blood lactate response in cyclists’; but because VT is a non-invasive method to determine anaerobic threshold & as this study concluded the Individual Anaerobic Threshold (IAT) & VT produced similar VO2, power & heart rate values (at least in a small population size); I am going to describe using this technique in pacing rather than jabbing yourself with a needle to test lactate!!
As described in this intensity model from Frankie Tan (Singapore Sports Institute) Polarized Training VT pacing borders Zone 2 of exercise intensity (above). In relation to heart rate, zone 2 is measured as a % of your maximal according to the table below.
Therefore by holding your heart rate at 85-90% max, this will bring an optimal performance at 50-90 minutes, before the athlete experiences cardiac drift through prolonged exercise. If you train consistently with a heart monitor you will be able to detect how your HR drifts and in a race situation enable you to detect your stamina level.
Give it a go; like Mark Allen I am sure you will find a marked improvement in your performance.
Enjoy reading the science behind endurance sport training? Like to hear the latest news & insight into the world’s toughest events? Why not sign up to our monthly newsletter, I only pick the best posts – right HERE