What Intensity Should I Be Exercising At?

The Australian guidelines for health state that we need to move more and sit less. Specifically, they recommend including 150-300 minutes of moderate intensity aerobic activity a week (and of course strength training twice a week!). But what is ‘moderate intensity’? Do you know if you are working hard enough or too hard?

Heart Rate

Monitoring your heart rate will enable you to determine your exercise intensity. If you have a heart rate monitor then this can be easy to track the intensity of your aerobic sessions but you can also take your heart rate manually. The range classed as moderate intensity is between 55% and <70% of your maximum heart rate.

You can estimate your maximum heart rate by the simple formula: 220 – age = maximum heart rate. Once you have your maximum heart rate you can work out the intensity range as a percentage of this. For example, someone aged 35 would have a predicted maximum HR of 185 beats per minute. Working at the top end of moderate intensity (ie. 69%) would mean that they had a HR of 128 beats per minute.

Be cautious with any heart rate monitor that records heart rate at the wrist rather than using a chest strap as these are not very accurate, particularly when moving at pace.

To measure your heart rate manually find your pulse at your wrist (the radial artery) or at your carotid artery in your neck. Using your index and middle finger, count the number of beats you feel in 20 seconds. Multiply the number of beats you count in 20 seconds by three to find the number of beats per minute. This is not so easy when you are on the move but you can always stop mid walk or jog to take a measure and know you are on track.

No Heart Rate Monitor? No Worries!

The intensity of aerobic sessions can also be determined using the Borg Rating of Perceived Exertion scale, or RPE. Perceived exertion refers to how hard you feel you are working. RPE is based on the physical sensations you experience during exercise, including increased heart rate, increased respiration or breathing rate, increased sweating, and muscle fatigue.

The scale is from 6 to 20 (Table below). As your exercise intensity increases, your RPE number will increase as you feel you are working harder. On the scale below 6 means "no exertion at all" and 20 means "maximal exertion." If you were sitting at your computer reading this your RPE of the physical activity you are doing is likely to be 6 (particularly if you are sitting!). 19-20 on the scale would be extremely strenuous exercise level. For most people this is the most strenuous exercise they have ever experienced.

Moderate exercise on the RPE scale is in the range of 11 to 12. If you have a noticeable increase in breathing rate during your exercise session but can maintain a conversation, then you are most likely in the moderate range.

What Exercise is Safe During IVF or for Maximising Fertility?

If you are looking to boost your fertility, either naturally or with fertility treatment, then exercise should be an important component of the positive lifestyle changes you make to benefit conception and the health of your baby. Knowing how much to do though can be tricky as each individual has different health considerations and different levels of fitness. There is no one size fits all approach when the end goal is so precious!

Different stages of an IVF treatment cycle require different exercise prescriptions. For men, the exercise you do in preparation for providing a sperm sample may be different to the exercise you do in the post-collection period. For women, your exercise prescription will differ between pre-treatment, stimulation, the period between egg collection and transfer day, and the seemingly forever two week wait. There will also be differences in your exercise prescription for frozen treatment cycles.

Just as you want a specialist extracting your eggs or handling your sperm sample, make sure you see an expert for exercise guidance. An Exercise Physiologist can help to create the right program to improve your chance of success needs to be based on your current health and activity levels, the cause of infertility and in particular your stage of fertility treatment. The scientific evidence is clear that the correct exercise prescription can improve your chance of success.