Ways to monitor intensity

So how do you know if you are training at the correct intensity and that you are conditioning the correct energy system for your selected event? There are many ways to monitor intensity. The best way is to use maximum oxygen consumption (VO2max). This is of no use to us being in the pool as it is measured taking blood samples. For this reason heart rate monitoring is used by most athletes to determine intensity of training. The easiest way but most subjective way to monitor intensity is by using a rating of perceived exertion (RPE). You can also control your pace at a given speed such as the critical swim speed (CSS). This will ensure that you train at the specified intensity. Lets examine each of these methods seperately.

Heart rate monitoring

During coaching I mostly use heart rate measures to determine whether a person’s pulse or heart rate (HR) is within a specific target zone for a set. It should be noted however that aquatic heart rates are mostly lower than heart rates achieved during comparable land exercise. Several theories exist to explain this:

  • Water cools the body with less effort than air. This reduced effort means less work for the heart, resulting in a lower heart rate.
  • Water reduces the effect of gravity on the body. Blood flows from below the heart back up to it with less effort, resulting in a lowered heart rate.
  • The water pressure compresses body systems, including the vascular system, causing a smaller venous load to the heart.
  • A gas enters a liquid more readily under pressure. In water exercise, the gas is oxygen and the liquid is the blood. So, more efficient gas transfer due to water pressure may reduce the workload of the heart.
  • Due to a primitive dive reflex triggered in the nasal area, heart rate and blood pressure lower when the face is submerged in water.

How to measure your heart rate during training

Taking you pulse

I found that the easiest way is to take a 10 second pulse count at the radial pulse on the wrist or the carotid artery at the side of your throat. The 10 second count is then multiplied by 6, to calculate the heart rate in beats per minute (BPM). Some coaches prefer to count HR for 6s and then multiply it by 10. Remember that you your heart rate starts dropping the moment you stop swimming. So take your pulse immediately after touching the wall.

Using a heart rate monitor

Monitors can be expensive and can interfere with training, specially the ones that need to be pressed every time a swimmer leaves the wall. Also remember that aqua heart rates need to be adapted from the land based values programmed into your watch. For swimmers training on their own this information can however be very valuable.

Heart rate calculations

In order to fully comprehend how the heart rate bands corrolate to intensity we have to understand the calculations that is used to set up the bands.

Maximum heart rate (HR max)

This calculation is used to determine your maximum heart rate during very high intensity exercise. It is estimated by the HR max formula which takes your age into account. It is calculated as (220-age). The formula is based on population averages and have been proven not to be very accurate due to physiological variance in individuals. We are not built like robots and have physiological differences that might result in heart rate values being over or under average.

Heart rate reserve (HRR)

To allow for some variance in individual heart rates the heart rate reserve calculation takes age and resting heart rate (Resting HR) into account. It is calculated as (220-age-resting HR). Resting heart rate can be taken when you wake up in the morning before getting out of bed or having coffee.

I use this formula to calculate the heart rate bands that my swimmers use to determine the intensity of their training.

Just remember that this calculation is still an approximation. One of my swimming buddies regularly recorded average HR for an hour swim at 155 beats/min while I will seldom get my HR over 130. Averaged calculations usually do not work so well for athletes in the tail ends of any normal distribution. This means that the calculations will be unreliable for very young and very old swimmers or for very unfit or super fit swimmers. You might have to further adapt you calculation as you get more experienced as a swimmer.

Next week I will show you how the calculations are used to determine heart rate bands and how this fits in with swimming intensities. I will also explain how to use Rate of Perceived exertion to determine intensity.