Anyone using this as a gauge to your workout intensity, especially cardio training? safe daw sa 85%. I always push to the limit hangang tumutulo na laway at uhog.;-) My friend usse it and he never pushes above 85%, slow down daw pag lumampas na. Parang nagset ka ng limit, eh pano kung kaya pa? I always try to workout to fatigue/failure. Unless it's one of those recovery days.