I have a question. I went to my gym for my "free" personal training session the other day and the trainer told me something I'd never heard. He said only to work out one muscle group per 7 days. He worked me through a workout that worked my chest and upper back and triceps and then told me not to work those again till the following week. He made up a plan that included working a different body part for each day of the week. I'd never heard that you had to wait that long between working the same part. Is that right?
And since I don't really care for the machines at the gym, they really intimidate me, I decided to take a body pump class. In that class we worked out with light and heavy weights for an hour working every muscle group pretty much. Does that mean I should only take that class once a week to get any benefit?

A bodypump class once or twice a week can be a fun workout. Plus, they're a lot harder than they look.

I think the "rest a muscle 7 days before working it again" is something that should be tossed out the window like a copy of Muscle and Fiction. Most studies (albeit most studies either suck or are biased/flawed) will show that typically more frequency (with considerations) of volume and intensity is better. That being said, I think you'll find your most productive gains in hitting a muscle group 2-3 times a week.

What you have to take into consideration is glycogen recovery and work capacity. I'd be hard pressed to believe there is a study that said a muscle needed 7 days of rest to fully recover. Fact is a muscle will lose strength when time between workouts is extended to long (not taking into the account of super compensation for competitive purposes).

Point A-your trainer sucks
Point B-your trainer sucks
Point C-your trainer sucks
...you can tell 'em I said so and you can take 'em this snippet of a rant with you.

Evo. Here is my routine. This also works just one muscle group a week. should I increase it in freequency ? This is something I am very confused about. Please comment.

Monday Chest/Triceps
Tuesday Legs
Wednesday off
Thursday Shoulders
Friday Back/Biceps
Saturday off
Sunday off

-Andy.

Well, I don't think shoulders need a day to themself. Shoulders can easily get worked enough with your chest and back days. I'm kinda' a believer in three set ups-
upper/lower, fullbody, push/pull/legs

Yours is nearly set up in the latter routine. I would set it up with 2 days on, 1 day off.

I like to do shoulder traps and lower back on one day
all chest and lats work on 2nd day
then legs, abs, obliques on the last day with a 2-3day gap before the next workout.

I find that this is the best way to get deadlift, clean and press into a weekly workout. this way your working your legs and lower back twice which are the most improtant muscles for most sport and general health.

I also find that Its better to work chest and lats as I am a fan of the decline bench press where the lats play a major part as a fixator muscle.

many ppl dont but it is also best to work the traps and shoulders on the same day as they need to work together for lifting and pressing.

oncyou feel ready you may even want to do some isolation arm work on the final day.

If you are a bodybuilder and your training sessions are VERY intense, and your goal is to gain muscle, then I will have to agree with a 5-7 day rest for repair/rebuild.

However, this is all based on goals, diet, etc......

Its all based on personal opinion but like LV said, unless you're a serious bodybuilder, you don't need to split each group up weekly. You will see most people split up their routines into three days a week. Chest/tris, Legs, Back/bis/shoulders. That is a common split. You will have 5-7 days rest between groups, but you will be focusing on other groups during that time.