you have to seperate the body into 2 parts the CNS and skeletal muscle. skeletal muscle recovers from high intensity exercise faster than does the CNS. that being the case the muscles can be exercised while the CNS is not taxed much. technically you could train the same muscles daily if you used loads less than 50% of the 1RM as they do not cause microtrauma to skeletal muscle or tax the CNS.
Yes, the CNS has a slower recovery rate than skeletal muscles. And yes, if intensity is appropriately low you could theoretically train muscle groups several times over in a day without overly stressing the involved muscles and/or CNS. However, (a) how beneficial would this be for performance, and (b) in the context of cutting how is this supposed to augment the fat loss process?
The whole concept of metabolic high-rep training on a cut (without even going into the further arguments of "sculpting" and "toning") is somewhat flawed. While there may be arguments for certain scenarios to show minor metabolic benefits versus higher-intensity, low-rep training, any decrease in intensity (intensity as a measure of relative effort) will result in a decrease of energy expenditure. You can perform 20 low-intensity reps, coast through the first 12-15 reps, and find yourself breathing heavy by rep 20 -- or you can perform a 5-rep set and be panting by the 4th rep. It's all relative. It works the same with running versus walking. You burn virtually equal calories over a distance regardless of time. The only difference is measuring against time elapsed the faster runner burns more calories than the slower runner. It's all relative.
Moreover, there's more to achieve when cutting than just fat loss. In fact, as diet should be the sole means to that end, training should be directed specifically for maintaining muscle mass. When in a calorie deficit your body searches for alternative fuel sources; incidentally, muscle protein is a potential fuel source -- what bodybuilders and other athletes want to prevent. It usually takes more than just a high-protein, low-carb diet to convince our bodies to revert to only fat, and not burn our hard-earned muscle. Performing many high-rep sets doesn't necessarily tell the body it needs to keep that large mass of muscle. You need to tell your body it needs to keep that mass at any costs, without working too hard to convince it -- hench low-volume/high-intensity: this method efficiently triggers to the body that its strength and mass needs to be preserved.
cardio or resistance training can both be used as a form of active-recovery. intensity is what dictates the frequency of training.
Very true. However, when cutting, as fufu said, the body's healing abilities are greatly hindered by calorie deficit and subsequent hormonal/nitrogen imbalance. Less is more.
in terms of bulking cardio like HIT increases the VO2max which enables the person to train longer and harder during high intensity resistance training sessions. the small loss in calories is far worth the 10-15 minutes you can spend 2x a week doing it
I agree that brief HIIT training (as per Built's "Daredevils are shredded" article) is useful in moderation when cutting. This would be used purely for stimulation and release of FFAs -- not athletic performance.
you also want to keep bf under control during a bulk and cardio can help with this. insulin sensitivity and nutrient partitioning determine how much fat free mass and fat is gained during a bulk
Cardio is highly useful on a bulk for many reasons, but I don't agree that one of them is fat maintenance. Diet determines how much fat you'll gain on a bulk. You can eat 1000 calories over maintenance, and hop on the eliptical to burn off 600 calories, with a net surplus of 400. Or, you can simply eat 400 calories over maintenance, and not waste your time. It's the wrong reason to perform cardio. Most people who use cardio for this reason don't apply themselves properly; it's not part of their training -- just justifcation for over-eating.
When applied properly, cardio can not only improve one's general health considerably but augment even the most intensive hypertrophy program.
