How much cardio is too much?

[Duncans Donuts]

Doing cardio for extended periods of time will cause your slow twitch fibers to stop growing, even if you continue to lift heavy.

That's defitently not true..

The body uses the slow twitch fibers for endurance

The body uses muscle according to the size-recruitment principle (except in very rare cases, in which it has been suggested or speculated on that slow twitch fibers can be bypassed in explosive lifts). When you bench press 300 pounds, you are using slow twitch fibers.

 

[CowPimp]

From what I have read (and that's a disclaimer cause someone will surely disagree with me on this)....

You are correct so far.

Doing cardio for extended periods of time will cause your slow twitch fibers to stop growing, even if you continue to lift heavy.

Actually, your slow twitch fibers are what will hypertrophy if you do endurance exercises. However, this will occur at the expense of faster twitch fibers, which are responsible for serious mass gains.

The large, fast twitch fibers can continue to grow, so mass increases are technically possible.... but since the smaller slow twitch fibers make up 50% of the total, it becomes much more difficult to see gains in mass.

Think about it. If slow twitch fibers make up about 50% of your total muscle fibers in the average person, then so do fast twitch fibers. The difference? Fast twitch fibers are capable of hypertrophying to a much greater degree than slow twitch fibers. As well, slow twitch fibers do very little for strength.

The body uses the slow twitch fibers for endurance and since they consume energy, the body attempts to make them as efficient as possible. I believe this is one reason why you never see marathon runners gain much mass, even though they exercise an incredible amount of time.

The body cannot make fibers more efficient. However, if myofibrilar hypertrophy occurs, then the fibers become larger and increase their force output potential.

The body can, however, make neuromuscular coordination more efficient.

 

[MTN WARRIOR]

And the reason that marathon runners dont ever put on any mass is not because of the fibers, it is because of the diet and exercise regimen that they follow. They put in carbs for fuel and conduct hours of cardio each week which burns it off. They do not want bulk because they would have to carry it around when running and that would slow them down.

 

[SlimShady]

Ok, gotcha... I wasn't argueing a point or saying this was correct, just repeating something I recently read in a magazine..

 

[Sissy]

Hey SlimShady, i happened 2 see eminem on Mtv the other day and gave ya a thought? It sounds like this "how much Cardio" thing could have some different schools of thoughts on the different body types?

_________________________

i could B wrong..a doctor i am not.