Just need some advice on this please from anyone with experiance. As an example i had a quick treadmill run yesterday. 23 min run 11 min spent at 80-90+% The rest was spent at 70-80% (before i realised i could do 80-90%) Is it advisable to stay at 80-90% as long as possible? Will i get fitter quicker keeping my heart pounding? I hammered it but when i had to slow down i did untill the HR got to 80% then started up again. Are them rest periods cheating?