After three days in a row I do get tired. The fourth day I'm usually rubbish at the gym for cardio and focus on strength training. The next two days at the gym can start off good on one day but end in a fail on the final day. But the more I do it, the better my results are and closer to getting five solid days.I'm also trying to compact the workouts so that I can get 60 minutes of this intense cardio in two hours instead of three.At this level it is important that I get 7 to 8 hours of sleep. Plenty of water. And good, nutritious food stuffs. I'm happy to say the junk foods that I used to enjoy actually bring me down now and impact me in a negative way. So I'm less likely to have 'cheat days' and such.