How much cardio is right for me ?

[xplicit]

Im 179 5 10 i dont know my bf i havent had time to go and get it done wit school and work. I have a pretty good diet but latly the last 3 weeks i have found my self eating a lot of cookies and chocalte and im gettng nervous ill get fat if i dont break out of the habit. I work construction and figure between that and the gym i am burning a good amount of calories i just dont have the enrgy to do cardio at the gym. I walk 30 minutes a day when i take the train to the gym and work.

My shit is all fucked up i need to rethink my whole routine i need to add in legs and cardio but i can only go 3 times a week 2 muscles a day so im there for an hour and a half so i dont know what to do. I been training 2 years already and i still feel im not working out hard enough or smart enough. You hear so much and read even more and everythign seems to contradict it self... some people work out 5 dyas a week and some say rest and spread it out and etc

I jsut had to ramble a bit sorry fellas

[Buddha_Red]

If you add 30 mins of cardio after your workout atleast 3 times a week you are good to go in my opinion.

Sure more is sometimes better, but really listen to your body and it will tell you if your working out too hard.

[TheChosen1]

Buddha_Red is correct. Technically, the body begins burning bodyfat/energy after 20 minutes of cardio. Therefore 30-45 minutes X 3-4 days a week is sufficient.

[defdaz]

Dude, not flaming ya - just genuinely interest - where do you get that time period from? I'd love to know if it has any scientific credence.

Reason for asking is that the aerobic slow twitch muscle fibres always contract during muscle contraction - there is an order in which muscle fibres are contracted and always the slow twitch fibres are called first.

One reason for this is that the slow twitch fibres allow for better control of light load movements (smaller bundles of fibres compared to fast twitch bundles).

As this is correct it is my understanding that aerobic oxidation occurs immediately and at all levels of work. Anaerobic work occurs if the load is too great for the slow twitch fibres alone to handle and hence fast twitch fibres are recruited (and thus glycogen energy reserves begin to be used up).

Therefore, if cardio work is done at a level where anaerobic work is minimal all energy will come from aerobic oxidation.

The question is why would it take 20 minutes to 'ramp up' the supply of fatty acids to the muscles for fat oxidation to occur in significant amounts?

I don't think this is so - and I think this 20 minute theory actually comes from the point during relatively hard cardio work where the stores of gylcogen are used up and the vast majority of the energy requirements must be met by fat oxidation (called "hitting the wall"). Until this point glucose has been contributing to the higher requirements not because there isn't enough fat being supplied but that energy demands are higher than can be met by the fat oxidative capabilities of your slow twitch fibres.

At this point the work becomes 'harder' and the intensity of the cardio is dropped a bit to adjust to the new level that energy can be supplied.

What do you guys think? I can feel a google search coming on, lol

Daz

[xplicit]

I though you dont actually start burning fat till you hit you peak resting heart rate??? Is that correct? I remeber gym class my teacher explaining it but i forgot exactly the process of finding it out and if it is correct in determing when you will brun fat

[defdaz]

No that's complete rubbish. They say that 65% ish maximum heart rate is the best rate for ideal fat burning but I don't agree, not for bodybuilders anyway - less intense cardio for minimal muscle wasting is the way to go.

Daz

[brad fuel]

defdaz i see your point about the aerobic system always in use. It is true. Think about it ppl. When you do Anaerobic work you're producing/using a lot of energy correct? yes. Aerobic work is low level activity right? okay now Anaerobic glycolysis produces 2 ATP. Aerobic Glycolysis produces 36-38 ATP. So obviously the aerobic system must still be in use to create all that energy.

Now about the 20 minute theory. ALmost all energy comes from directly from glycogen. Carbs, FFA, Protein are all changed to glycogen before they're broken down for energy. So the first to go is muscle glycogen, then carbs, then fats, then proteins. of course there's overlap. So i'm guessing the first 20 mins is to use up the muscle glycogen and carbs.
I remeber seeing a really nice graph in my physiology text book showing % of substrate vs duration of exercise. Too bad i don't have a scanner. Anyways the graph does show increase of ffa usage over time and decrease of glucose usage over time.

[xplicit]

So how long and how intense should cardio workouts be if you want to burn fat but still maintain muscle?

[brad fuel]

that is a hard question to answer. Your muscle fibers will always prefer to be more efficient, so they will like to be more aerobic. They like type 2a rather than type 2b fibers. So if you do large lengths of cardio you'll shift towards 2b and possibly 2c fibers (using the 5 isoform model). In other words, yo'ure not gonna get very big