Hi all. My 5 minute "speed" walks are going well! I spoke to my son about what I'm doing - he's in the medical field and also qualified as a personal trainer some years ago, as he's really into health and fitness, being an ultra-marathon runner! (I know - how did I get so unfit? I regularly ask myself this!) Anyway, I quizzed him about what my heart rate should be during/after my "speed" walk and he gave me a formula. He said I should take 220 and subtract my age from it. I'm nearly 68, so that gives me 152. He then said that fat-burning and cardio benefits will start at 60/70% of that number - that comes to 91/106. So my heart rate should at least be above 91, preferably above 106. My heart rate at the end of my 5 mins is 110, so hurray, I'm within the limits! But he also warned me not to let my heart rate get above 120 - to rather extend the time I spend walking. I intend to build up to 10 mins anyway, so this fits in fine with my goal! It's good to have confirmation that what I'm doing is the right thing and also to know how far I can safely push myself! Kids do have their uses sometimes!! Lol!!