Most I can work muscles

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Yes you are right that you can't work your muscles more than once or twice a week, the only muscles that don't apply to that are the abs. Some believe you can work your calves more often as well and others might even throw traps into it but in reality they all need more recovery in my opinion. So abs you can work 3 or more days a week but not your other muscles

The reason you can do abs more is because of the kind of muscle that they are, i.e. smooth muscle. This kind of muscle cell recovers quickly thus you can train abs every day if you want to. Calves are pretty hardy muscles, but they do need recovery time.

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First off let me just bring this to the table, when youre training a specific muscles group there should be two types of training days. Your "A day" which would be the day you go heavy and close or to failure and then your "B day" which is a maintance day. You can train any of the muscle groups twice per week, but you shouldn't train heavy every single time due to the fact this will lead to overtaining and it will lead there fast. As for forearms little bro, I would personally say to just do them on the day you do biceps so you train it will another "pulling" muscle. Hypothetically i suppose you could train them every other day since they are a small muscle and tend to heal quickly, but still over doing it will lead to overtraining. Just remember, youre muscle grow when they are resting so you need adequate rest, the rule i follow is 2 full days of recovery for small muscle groups and 3 for larger muscle groups. Any other questions feel free to ask Malic, thats what were here for.

I belive that smooth muscles are the muscles of the heart and other organs.

Basically, your muscles needs at least 48 hours to recover, though this can vary a bit dependong on the person, their age, and any AAS use.

Some folks argue that the stomach is different, and the calves and the forearms are different becasuse they are used all the time.

But I would never work out any muscle five days a week.

I do a three way split (chest/back, shoulders/arms, legs/abs) and work out four days a week. So I get about five days reast before I hit the same exercise again (though there is some overlap in the muscles worked).

If you are not doing so already, start doing a two way, or three way split. If you want to work out more then, you could always add a day and still not hit the same body part too often.

But you need rest to grow, and if you overtrain, you will get worse results.

Hmmm...I'm not sure why I have always heard that abs were smooth muscle. I just found a link that explains that they are not. Generally, smooth muscle is involuntary thus it is found in your intestines and stomach for example. Muscles that are under voluntary control are called striated muscle or skeletal muscle. Since you can voluntarily contract your abs, they must be skeletal muscle. Cardiac muscle is also different from smooth muscle and striated muscle but has characteristics of striated muscle. Very interesting article.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Muscles.html