I am currently training for a marathon and working on building my mileage back up prior to the race. I am also lifting two days a week (one upper body, one lower body day). I was wondering if it is counterproductive to do a "longer" training run (8-10 miles) 2 days post leg day where I was doing heavy squats, or if one day of rest in between is enough? Anyone have any insight? I don't want to undo any of the work I have put in.