In a typical fitness center you've got a range of choices in fitness related services. The common breakdown is:
1) personal training
2) small group or specialty training and
3) "group exercise"
Those are in order, by the way. Personal Training, for the average "health seeker" or aspiring fitness enthusiast, is often your best choice (with a good personal trainer - which should be another post altogether). You've got one-on-one time with an industry professional to ensure you're getting the most from your efforts, continually progressing and improving as well as enjoying the process as much as possible.
Small group training, often called "specialty training" is, of the three, your second best option. A group of 3-5 people all receiving instruction on similar activities (i.e. kettlebells, TRX, etc) to the a mutual intent; getting a good workout. And with a small group it is possible to achieve this while even being able to emphasize basic technical principles and movement quality. This is generally your best "get-in, get-out" option with a professional as you can still receive individual attention.
Last on the list is "group exercise." These go back to your "step classes" and such of the '80s. The Les Mills program is commonly implemented now in big box gyms and other facilities but the gist remains the same in other programs - when I move, you move. Now, I'm not entirely against these "classes" as nearly everything can have its place but you won't find me following along with or leading one. (By now, you've likely identified my overuse of quotations marks and parenthetical thoughts but the word "classes" being in quotes above has a very deliberate meaning to it.)
When I think of classes I envision an environment of instruction, learning and performance. Frankly, this is not what I've observed of group exercise "classes." There is certainly activity but seldom have I seen any great deal of coaching or teaching or, dare I say it, progressing taking place. Concordantly, its tough to imagine any substantial learning is going on either.
Rather than continuing to ramble on let me just draw a comparison between PT and GX:
Personal Training process:
1) Consultation regarding your goals, injuries, past exercise experience, etc.
2) Fitness Assessment: measurements of anthropometric variables (circumfrences, etc), movement screen (identifying weaknesses... with-which you are riddled), strength tests, cardio tests, etc.
3) A fitness progression* designed around your goals, limitations and interests
4) Continued accountability of weekly meetings to guarantee progression, examine training journals and nutrition logs and discuss new lifestyle strategies
5) "Homework" workouts and recipe ideas for the next week
Group Exercise process:
1) Walk in
2) Do what I do
3) Burn a few calories
4) Continue to mistake activity for accomplishment
Am I being a negative prick about this? Yes. Am I generalizing? Some. Can GX "classes" have their place in a well rounded fitness program? Sure. Is it you best option or even a good option for many people? Absolutely not. If you're a beginner this is literally being "thrown to the dogs."
If you can't look at your efforts of the last, let's say, 1 month and show me your improvements (literally show me, pull out your training log and show me the numbers - strength gains, bodyfat loss, etc.) then what you are doing, no matter the class or activity, is spinning your wheels. From my observations, showing up to a no-obligation, little instruction class with 20 other people is not optimizing your time in the gym nor is it doing much to improve your understanding of health or your health itself... its spinning your wheels.
*My use of "progression" in place of "routine" is another topic altogether, also.
