Gary Null, health expert says you need at least 45 minutes of intense physical activity to reap the benefits. I've been consistently working out in all forms of activity six days a week for almost a month and my resting HR went from 84 to 60. Woo hoo! Sitting up at desk and doing laundry, my heart rate is about 80 and when I'm at my job, pushing the med cart it's about 100.