
Originally Posted by
pebble
Really? Cardiovascular exercises at intensities of say 60% of one’s heart rate reserve [(220-age - resting HR)x intensity (.6) + resting HR] does not burn as much fat as one would think. It is only about 26% of total calories coming from fat. The primary method of fat oxidation is fuelling your body at rest when hypocaloric. Cardio's biggest benefit is creating that caloric deficit (glycogen used needs to be replaced therefore CHO ingested go through glycogenesis to be stored in the liver and muscle) This means the body needs to fuel the rest of its major organs, which by the way are much more responsibly for metabolic demand than muscle, will utilize adipocyte lipolysis and beta oxidation.
Diet is the biggest factor in reducing body fat. You can do all the cardio you want, but if you are still hypercaloric you will be gaining weight.
As for the debate about reps and energy systems, higher rep ranges do not utilize fat. It is an anaerobic exercise that produces lactate as a result of buffering metabolic acidosis - result of CHO in the absence of O2 (anaerobic glycolysis). It is that simple. However, this does create a deviance from homeostasis that result in metabolic disturbances, but so does using lower rep ranges that alter the ATP-PCr energy system. To add to that lower rep ranges result in more micro trauma to the sarcolemma and myofilaments that ultimately need to be repaired stronger than they originally were. Both increase metabolic activity post exercise.
The best bet to maximize cardio’s direct fat loss effect is a short stint of very low intensity cardio post resistance training. RT causes the release of catecholamine’s and hormones (HGH, epinephrine, and norepinephrine are of most interest) which are known to promote lipolysis. We also know that RT uses glycogen (muscle, plasma, liver) during RT (explained above). This promotes a very favourable environment of beta oxidation (fat oxidation - use). If you do some light cardio trying to keep your HR under 130 (due to sympathetic vs parasympathetic nervous system and endocrine response) you will increase the amount of fat you are burning compared to cardio at other times of the day [It is very similar to fasted cardio in the morning, but with larger driving force for lipolysis (getting the fat of the adipocytes)].
So hypertrophy is the goals?
Well not all rep ranges are created equally as has been suggested here. Yes time under tension (TuT) is very important but, not all tension is created equally do to the fibre types it stimulates. Higher rep ranges (12-15+) do not provide enough tension to elicit enough of a response form type 2 fibres (which grow the most). This rep range will act on fibre type 1 which has little room for growth as it is not their primary role (postural and continuous movements).
Moving to lower rep ranges 1-5 also causes a problem. This time we have plenty of tension, but not as much time under that tension. We are stimulating the right fibres, typ2, but not for a long enough period of time (generally want about 40 seconds). This is where shorter rest can help, but the problem is time is not completely additive so less hypertrophy can be experienced here.
The sweet spot really is 6-12 because it provides the best combination of time and tension as the stimulus to drive adaptation.
Things get a little more confusing when you remember that not all hypertrophy is created equally. The two primary types are sarcoplasmic hypertrophy (SH) (muscle cell fluid, enzymes, and glycogen primarily) and myofilament hypertrophy (MH) (growth of the contractile components of the muscle – actin, myosin …). The higher the reps the more likely you are to promote a higher ratio of SH. The lower the reps the more likely you promote a higher ratio of MH. One other point to note is that SH is normally a softer muscle, whereas MH is denser.
Well this post just got really long so I am going to cut it here.
EDIT -
Hypertrophy can be seen at all rep ranges with a proper diet and training, but the quality and quantity will differ.