first, what workouts do you have so i can help with a rotation? do you do your cardio in a gym as well or have access to an ellipical, exercise bike or treadmill? for you final question, no you aren't doomed to fail splitting your workouts like this as long as you stick with makeing time for them. the thought of this sounds great for me but i know for me, i'm too tired at the end of the day to do another workout so this wouldn't workout for me. since i don't know what type of workouts you have i will just form a schedule based off cardio and strength. i know a lot of people like doing cardio in the morning and weights in the evening but that is dependent of the person. so switch around that if you dont like how i have it
monday a.m. 30 bike/ellipical/or walking----p.m. chest and abs
tuesday a.m. 30 min high impact cardio (running, first 5 intervals of imax 2 or 3, kickmax intervals only, etc.)----p.m. back
wednesday a.m. 30 min cardio (something different then monday---p.m. triceps and abs
thursday a.m. low max or low max 2 (can do the timesavor version)---p.m. biceps
friday a.m. 30 min walk/bike/ ellipical----p.m. legs
saturday a.m. 30 min walk/bike/ellipical----p.m. shoulders and abs
sunday off
or you could do:
monday a.m. cardio p.m. chest and tris
tuesday a.m. cardio p.m. legs and abs
wednesday a.m. cardio p.m. back and bis
thrusday cardio only a.m. and p.m.
friday: total body
saturday: cardio only
there are many ways to split what you want to do. what are your goals? you can work one body part as i listed, group body parts, full body workouts. You don't need to do high impact to get results either. you can easily do sprints on a bike or ellipical and get great results. the frequency of lower body workouts depends on how heavy you are lifting. if you do heavy once is enough. a lot of people do 2 times and there are even people who lift light everyday for legs (free style training). sorry this is so long. i hope this helped some. i just need more info to give you a better plan.