Fruitful or hindrance. It would be of benefit to speak with a certified trainer, in the area of goal oriented exercise that your interested in. I do go to the gym. I mix up my programs and do circuit training as well as dance. Cardio is a great benefit for stamina in dance, as well as everyday life. Dance is not my only outlet. I have yet to lose flexibility even with free-weight workouts - then again I'm not a body-builder nor interested in bulking up. Toned and fit is more my goal. Without the assistance of a qualified trainer - at first - I really would have been lost as to how to accomplish fitness goals that could merge into dance as well.

THere is no reason why building muscle tone, endurance and cardio-vascular fitness will bulk up muscles significantly. For muscle bulk we're talking about small reps of heavy weights. Muscle tone and endurance is lower weights, higher reps.
Flexibility and balance can be worked on too. Cardio-vascular fitness has negligible effect on muscle bulk and can only improve dancing of all forms. Good muscles are essential to support a wide range of movements without injury. How can a standard ballroom dancer keep a good frame without strong core muscles? or perform strong, controlled movements throughout a day's competition without muscle endurance?
There is performance-specific fitness of course, but it's based on a good solid foundation.

"How can a standard ballroom dancer keep a good frame without strong core muscles? or perform strong, controlled movements throughout a day's competition without muscle endurance?"

They can't, but that's not the important question. The important question is if the specifically appropriate form of these things are to be gained in a fitness facility or by practicing the actually targeted activity - by dancing.

We might also ask how your primitive ancestors got in shape for (taking a little dramatic license) running down mammoths and running from sabre toothed tigers - probably not in the gym, but first by chasing each other around the campfire as kids, and later by leading the life they needed to be in shape for on a daily basis.

Just one look at the muscle tone at the back of the lady Latin Dancers will show that they do some kind of Gym work. You will find the same with the Standard Style also. In Standard the teacher that I go to attends a Gym three times a week. You've only to put your arm and hand around her to feel the tone of her body. She has a personal trainer for the Gym work.

My wife teaches fitness classes called "Shape and Tone." Those are probably the key words. It is good to tone your muscles and make sure your body is in good shape. That means a nice mix of cardio and strength exercising. It does not mean bulking up with free weights and getting muscle-bound. Dancers are strong, but not disproportionately. I am a boxing fan, as another poster suggests, and I do believe dancers could take a cue from a boxer's training regimen. It is mostly about flexibility, endurance and quick feet and hands. It is not about massive arms and chests. That's for football linemen, not athletes (and dancers) who have to move quickly and precisely, even though in this day and age, the best football linemen are also learning that quick moves with their feet are just as important as bull-like strength.
I am middle-aged soft now, but feel I am in pretty decent shape. I am not "tough-guy" strong with big arm muscles, but I have good endurance and very strong legs and knees for my age. So I now rely heavily on stretching exercises such as yoga and some resistance strength exercises on a machine called Total Gym. That, and a lot of dance practice, I hope will keep me clicking for some time.

dhen. I find that holding my arms in the correct dancing position is an Isometric type of excercise. I find that I keep good muscle tone in my shoulders an biceps area without having to do any other exercise for that part of the body.

Polished, no doubt about it. No matter how much exercise we have completed in a given week, when we have dance lessons for an hour or more, and most of it is in ballroom position and holding frame, we notice it in our arms and shoulders.
From that standpoint, it is a great strength builder.

I feel I can respond to this because I am regular gym rat and I have been dancing ballroom for two years now.
I am 5'9" tall, 50 years old, weigh 250 lbs and can bench 300 lbs.
I lift in 4 times a week for a hour to a hour an a half. I lift for both strength and endurance.
True I stretch but everyone should.
Yes I have large arms but they do not get tired from holding them up for long periods of time. When I go to our dances I normally sit for one dance per hour. And have energy to spare for an after party when its over.
I feel being strong has many benifits and advantages. For one, I can dip a girl so low her hair is on the floor and she need not worry about being dropped.
I stongly recommend using wieghts to increase your strengh and endurance. You'll enjoy the results.
~Carl

Well I didn't even expect so much feedback , thank you all.

I didnt specify , but of course my gym related question was aimed at cardio/tone programs(low weights , high reps) I don't really like the bulk look and it wouldn't fit me anyway :)

I have proceeded with my idea.
Aside from spending 2-4 hours 5 days a week in the studio , I have enrolled in a gym which Im attending 3 days a week.
Each of those days I do 4-5 abdomen and lower back exercises + one muscle group calves/thighs/back. Pleasing results in tone and endurance so far without weight gain.
As for cardio I find running/biking too boring. Thought I highly recommend roller skating , jumping off verts and balancing on rails is almost a perfect workout for anyone in the dancesport community :) !

For what its worth. When I came back into dancing after a lengthy absence I bought a treadmill. I went fairly hard for two minutes and gave myself a 30 second rest and repeated five times. I did this a couple of times a day. I figured if I had to dance five dances I would be able to stay the distance, which I can at this present time.