And if you do the HIIT type stuff you should be so thoroughly wiped out that you won't be able to do it more than three times per week... As far as supps to stave off catabolism you should be eating enough prior to your work-outs to prevent that from happening anyway. Based on a recommendation from Someanddone and MAYO I've began bracketing my workouts with whey/maize pre-workout; maize post workout and 40 minutes later whey. BCAA's intra for mental health
^^ YEP...i have learned that long duration low intensity cardio saves more muscle than HIIT cardio. I am also a huge advocate for morning cardio prior to post training. I have used both in the past and get best results from morning cardio
low intensity will burn more fat as high intensity will build endurance. I always tell people to mix in some sprints once a week at least if you are still young enough to hack it! Using high intensity cardio to build your low intensity cardio endurance is the way to go. Most baseball and football players do not utilize low intensity cardio nearly as much as high intensity cardio (other than to rehab an injury or similar situation). This is because most of these guys are in great shape already and their sports require "bursts" of speed or strength for short periods of time. So, if you are a powerlifter, it would make sense that you would want to do some high intensity cardio every once in awhile to try and evolve your lung capacity. I'm not a powerlifter myself, but I would bet that lung capacity and breathing is one of the things that makes a difference once you get to the top levels.
HIIT will burn more fat, increase glycogen stores, increase VO2 max and all cardio related measures of efficiency. If 150 seconds of full body explosive movements are catabolic to the body, imagine what 30 minutes of sustained heavy lifting should do. There are very few sports where low intensity cardio is beneficial, powerlifting, bodybuilding, they aren't a part of that category.
The impact of two different modes of training on body fatness and skeletal muscle metabolism was investigated in young adults who were subjected to either a 20-week endurance-training (ET) program (eight men and nine women) or a 15-week high-intensity intermittent-training (HIIT) program (five men and five women). The mean estimated total energy cost of the ET program was 120.4 MJ, whereas the corresponding value for the HIIT program was 57.9 MJ. Despite its lower energy cost, the HIIT program induced a more pronounced reduction in subcutaneous adiposity compared with the ET program. When corrected for the energy cost of training, the decrease in the sum of six subcutaneous skinfolds induced by the HIIT program was ninefold greater than by the ET program. Muscle biopsies obtained in the vastus lateralis before and after training showed that both training programs increased similarly the level of the citric acid cycle enzymatic marker. On the other hand, the activity of muscle glycolytic enzymes was increased by the HIIT program, whereas a decrease was observed following the ET program. The enhancing effect of training on muscle 3-hydroxyacyl coenzyme A dehydrogenase (HADH) enzyme activity, a marker of the activity of beta-oxidation, was significantly greater after the HIIT program. In conclusion, these results reinforce the notion that for a given level of energy expenditure, vigorous exercise favors negative energy and lipid balance to a greater extent than exercise of low to moderate intensity. Moreover, the metabolic adaptations taking place in the skeletal muscle in response to the HIIT program appear to favor the process of lipid oxidation.