Why is heart rate used in sports?
Many athletes and coaches measure physiological parameters to quantify the work performed by the human body during a workout. One of the most commonly known parameters is heart rate.
While working out, your body is performing a specific workout routine. This is scientifically referred to as the external load. The goal of this workout routine or external load is to trigger a response of the body. The response to this external load is called the internal load.
During a workout, the body reacts to what is required from it by for instance adjusting oxygen intake, adjusting heart rate, activating energy systems, dilating blood vessels, … As there is a direct effect on heart rate when a change in internal load occurs, it is a useful parameter to monitor this internal load.
Figure: An external load leads to an internal load, which in turn leads to a training outcome.
How is heart rate typically used in swimming?
Training programs are often designed using heart rate zones to indicate effort. Heart rate zones can be used to organize different workout intensities. The heart rate zone system is used to measure the internal load of the body during workouts. It also translates the measured value to a respective training effect.
The figure below shows a typical split of heart rate zones and their respective training effect. As you can see, these zones are also at times indicated by color codes through a system introduced by famous swimming coach Jon Urbancheck.
Figure: the Urbancheck zones.
Let’s briefly explain the Urbancheck heart rate zone system. On the left you see the different color codes, followed by a description of what these colors stand for.
The description goes from a white basic aerobic training to a green lactate tolerance training. Depending on what workout routine you follow, you are performing a certain color code intensity. If you amp up your training intensity you will gradually rise in color code.
The table above also shows an indication of the energy zone you are in. Swimming sets are supported by energy from different sources, depending on the duration and intensity of that set.
EN-1 means you find yourself in a moderate endurance zone. After this you enter the EN-2 zone which is all about threshold training. EN-3 is the last zone before you enter sprint and concerns over-threshold work. The SP-2 classification involves your best average and race pace.
We will expand more thoroughly on the workings of different energy zones and thresholds in a future blog post. Of course, the higher the color code you’re in, the higher your estimated pace. The chart above shows pace in function of threshold, but there are different ways to communicate these.
Every zone finally corresponds to a specific heart rate range. These values differ individually and are sometimes expressed as percentages of maximal heart rate. Heart rate is however influenced by more factors than just external training load. We will go into this in the next section.
How not to use heart rate zones
Heart rate zones are often misused or misinterpreted when being set up or used to evaluate a training session. The body of science is very clear: heart rate is not solely an indicator of internal load induced by the training load on the body. Heart rate is the result of multiple load factors onto the human body.
The figure below shows a few of many factors that influence heart rate on top of an external training load. Autonomic nervous system, hormones, position, exercise, emotions, gender, age, temperature of the body and baroreceptor reflexes influence the human heart and therefore its heart rate.
Note that these are just a few of all the things that affect heart rate and that there are a lot more things to take into consideration when measuring your heart rate. Heart rate is also an individual measure, in that way that body size and composition as well as other genetic factors influence your heart rate level at any zone. If you want to know your personal training zones, we always recommend consulting with a certified professional on a regular basis.
Figure: Heart rate is influenced by many parameters.
How to use heart rate zones
Coaches and athletes should always be aware of the multi-factorial influence on heart rate when assessing heart rate during training.
Let's take an example. When an athlete is overloaded, it is possible that the heart rate of the athlete is higher during an aerobic set than usual. It would be wrong to conclude that the athlete is performing an anaerobic set because the heart rate is higher than usual. Instead, given the fatigued state of the athlete, it would be better to assess the fatigue of the athlete with a subjective measure. Doing this helps to understand that the higher heart rate is due to a tired body rather than trying to match the internal load indicator to the external load.
An important (additional) indicator of internal load remains to be the rating of perceived exertion, or RPE. A well-known scale to assess this is the Borg scale. The figure below shows this scientific scale. Scientific research shows that the Borg scale or RPE is often the best indication of training intensity as perceived by an athlete during a training.
Figure: Rating of perceived exertion (RPE) scale.
Take home message
Heart rate is one the most validated representations of the total internal load on the athlete’s body. Next to the external load from the workout, there are also additional factors influencing the final heart rate value.
For coaches, it is important to understand this effect and to act accordingly, acquiring as much information as necessary from their athletes in order to make a good assessment before possibly adjusting the workout.
For athletes, it is important to use heart rate as a way to get to know the workings of your own body. Going through age group training towards a seasoned athlete, you should get to understand how your body reacts to certain workouts or other loads, how it feels and how this is represented in your heart rate ánd RPE. The better you get to know your own body, the better you can use your RPE as a context for your heart rate for yourself and your coach.
With Swimtraxx One, you can track your heart rate during every swimming workout. The system allows you to monitor internal and external load so you can get to know how your body works during those easy or incredibly tough sets. The device also tracks multiple swim specific biomechanical parameters next to heart rate.