One of the best ways to determine how hard your body is working during your workout is to monitor your heart rate (HR). You can calculate your HR by using a heart rate monitor or by feeling for your pulse and calculating it manually.
Once your maximum HR has been identified (208-[0.7*age]) – the most your cardiovascular system can handle during your workout – you can identify target zones to work within depending on your individual health and fitness goals. It’s important to remember that some medications can actually lower your maximum HR so be sure to talk to your doctor to better understand what percentage of your maximum HR is appropriate for you to work within.
Your Target Heart Rate
If you want to get the most out of your workout then you should be working within your target heart rate (HR).Typically, in order to improve and not simply maintain your current level of fitness, you need to work within 70-85% of your max HR.
Talk to your trainer for more information.