Cardio and muscle growth

Question

I have spent 7 years doing practically no exercise at all and eating all the crap I wanted. Weird thing is that during all this time I have been pretty muscular.

Recently I started doing some cycling and the following day after the first session (which lasted like 8 minutes and left me exhausted) I noted that my muscles where like soother, like if they had gotten bigger.

I Have continued exercising, and I have kept seeing this. After cardio I am more toned, if I do no exercise like for 5 days or so muscle tone drops, but after another session it gets toned back.

I had always heard that cardio wasn't good for muscle building. So, why does this happen to me and until when will my over-all muscle tone improve with solely cardio?

Answer 1

The acute effect of exercising (any type of exercise) is that the muscles become engorced with blood. This serves to increase oxygenation, remove metabolites, deliver nutrients and anabolic hormones. A muscle that is engorged is, obviously, larger and tighter than one that is not. This is the reason behind your "toned" muscles". Another thing that happens during muscle contractions is that the neural imput it recieves increases. This has the effect of an increased post-exercise tonus; tonus is when a proportion of the muscle is contraccting, even in the absense of force production. This is another reason why your muscles feel harder after exercising, but this effect also disappears after a couple of days (even faster with warm showers and massages).

Basically, there is no change in the structure of your muscles the way you train. You exercise, and then wait for the effects to completely disappear before training again. In order to progress, you must stress your body. I would suggest you read up on "supercompensation". This is called the one-factor model of training and is kind of outdated, but still very similar to the more accepted two-factor model of training. However, unless you plan on becoming a professional, there is a minimal difference as far as results go.

On another note, I see that there are a couple comments about toning for the previous answer to this question.

"Toning is a myth" - Yes, in the sense that people portray it. Toning will not increase your fitness markedly, nor will it get your muscles stronger or harder. What people refer to when talking about toning is when slow twitch muscle fibers undergo sarcoplasmic hypertrophy. So, in one way, performing low weight/high rep exercise can increase muscle cross section area. It will not however increase strength. Also, the hypertrophic potential of slow twitch muscle fibers is much lower than that of fast twitch fibers. Aiming to get "toned", in the sense that people do, is a waste of time. Classical body building methods, medium weight/medium reps, are more efficient.

Answer 2

Resistance training for toning (aka endurance lifting) is used for toning muscles. There may exist a formal definition somewhere, but I like to think of it as

low resistance, high repetitions. 

So, when a person runs marathons, lifts low amounts of weight with high repetitions, or uses an exercise bike on a light setting for a long time, they are toning. Yes, cardio is the primary workout for running the marathon and exercise bike, but they are still toning the muscles that are being worked.

That was a practical example. I left my physiological definition of what happens to slow twitch and fast twitch fibers in my other pants pocket.

Exercising is a hobby of patience, so if you want to stay 'toned' for longer than a week your going to have to keep up a lifestyle of exercising for quite some time.