//Work Out Heart Rate Min - Max
function calc(form){
var maxHeartRate;
var minHeartRate;
var percentZoneMin;
var percentZoneMax;
var targetHeartRateLow;
var targetHeartRateHigh;
//Get form values
minHeartRate=parseInt(form.rest_hr.value,10);
maxHeartRate=parseInt(form.max_hr.value,10);
percentZoneMin=form.percent_zone1.value;
percentZoneMax=form.percent_zone2.value;
//Run our calculation
targetHeartRateLow=Math.floor((maxHeartRate-minHeartRate)*percentZoneMin/100)+minHeartRate;
targetHeartRateHigh=Math.floor((maxHeartRate-minHeartRate)*percentZoneMax/100)+minHeartRate;
//update our form
form.target_hr1.value=targetHeartRateLow;
form.target_hr2.value=targetHeartRateHigh;
 
}