Forerunner 405CX Owner’s Manual 5Using Accessoriessome 2.4 GHz wireless sensors,which can interfere with yourheart rate monitor. Sources ofinterference may include veryhigh voltage power lines, electricmotors, microwave ovens,2.4 GHz cordless phones, andwireless LAN access points.Heart Rate ZonesCaution: Consult yourphysician to specify heart ratezones/targets that are appropriatefor your fitness level and healthcondition.Many athletes are using heart ratezones to measure and increase theircardiovascular strength and improvetheir level of fitness. A heart ratezone is a set range of heartbeats perminute. The five commonly acceptedheart rate zones are numbered from1–5 according to increasing intensity.The Forerunner sets the heart ratezone ranges (see the table on page45) based on your maximum andresting heart rates set in your userprofile (see page 28).You can also customize your heartrate zones in your user profile ofGarmin Connect or Garmin TrainingCenter. After customizing your heartrate zones, transfer data to yourForerunner.How Do Heart Rate ZonesAffect Your Fitness Goals?Knowing your heart rate zones canhelp you measure and improveyour fitness by understanding andapplying these principles:Your heart rate is a good measureof exercise intensity.Training in certain heart ratezones can help you improvecardiovascular capacity andstrength.Knowing your heart rate•••