Good Day! The rule of thumb with exercise is to always warm up and cool down. The amount of time to warm up is 5-10 minutes and the same for cool down. We generally shoot for 20 minutes continuously at target heart rate or rate range.

Please remember that these recommendations are to be individually tailored depending on cardiac status, current fitness level and other such medically pertinent variables.

Congratulations on maintaining an exercise program. Good job! Feel free to write again if you have further questions. Kathryn Shattler, MS,RDN

Hi welcome to HCM
I have gone thru your query regarding target heart rate while on treadmill

Dear , Your maximum possible heart rate is generally considered to be around 220 minus your age. So, for example, a 20-year-old's maximum heart rate would be around 200 beats per minute.

During exercise, the muscles require more blood and oxygen to function properly.
The heart pumps more quickly and vigorously, elevating both your blood pressure and pulse.
Although a rapid heart rate can be a sign of health problems , resting during exercise actually helps to exercise the cardiac muscles and reduce your risk of heart problem .
So you can understand , rest in between is a necessity to reach your target sucessfuly .
Everyone's target heart rate varies slightly, and medications, physical and mental conditions and your overall health , intake of essential nutrients can greatly alter your ideal heart rate.
. Your body needs more oxygen during exercise, to compensate for the lack of oxygen supplied to your muscles and organs heart rate increases .To keep it under control during intense workouts -- drink plenty of water and warm up and cool down before your exercise. Breathe in slowly and deeply and then exhale slowly.
Food that is high in saturated or trans-fats like fried , fast foods , refined sugars and fine floor prducts , tea , coffee , alcohol , sleeplessness , dehyderation , constipation .worry ,stress all induce toxins in your body .
Avoiding is the best option to reach your goal .

Thus it's important to consult your doctor before beginning an exercise routine .
Hope this helps solves your query .Take care , All the best .
Don't hesitate to get back if have any further query