Do I need more lactate threshold work? Usually by mile 1.2 in a 5k or by mile 4 ish in a half marathon my legs are feeling very heavy and flat like they do in a mid tempo run. anything i should be doing to make this less noticeable? I know you're not supposed to feel a 100% fresh in mid race, but my cardio isn't labored in my races, its my heavy dead legs slowing me down. I run all my easy runs very easy with a HRM and only do one speed and one LT day in my week. Everything else is easy running or my long run. Thoughts?