There's almost never a situation where some set of muscles should be constantly engaged, and the stomach muscles in Samba are no exception. There should always be a tension and release. In this case, the tension is what causes the pelvis to tilt forward as the knees bend on the "a" count, and the release is the stomach muscles relaxing as you step on the downbeat.

However, while one set of muscles relaxes, another engages. On a typical Samba Walk, for example, you step on the downbeat with a hip lift. The stomach muscles are therefore stretched, but one of the lats will contract and squeeze the side of the back corresponding to the lifted hip, in order to keep the shoulders level. As soon as you move into your next "a" count, contracting your stomach muscles to tuck the hips again, that same lat muscle will relax.

Sincerely,
Jonathan Atkinson

Pelvic tilt -- hmmm -- maybe have someone sneak up from behind and goose you?

Actually, in my experience, the problems people have with Samba and with Latin hip action in general is not a lack of flexibility as much as it is a lack of coordination. Even with a limited flexibility, if the coordination and timing of the various body parts is correct, the dancing will look quite good.

The Samba action itself is pretty complicated and difficult to discuss in writing, but in a nutshell it's a combination of a bounce and latin hip action. The bounce is generally absorbed in the knees so that the overall level of the dancer doesn't actually change much. This point can be illustrated by the following exercise:

Stand with your feet together, flat on the floor, legs straight. Begin to lift your heels while at the same time bending your knees. Whereas lifting your heels would normally cause you to rise, bending your knees would normally cause you to lower, and the two actions when done simoultaneously and timed correctly cancel each other out.

So when people tell you that the "bounce" action of Samba is absorbed by the knees, this is the action that they are describing. It usually happens on the "a" count immediately prior to the downbeat, and tends to cause the pelvis to tilt forward.

Now in addition to tilting forward, the hips can also push out to the back, to the side, and rotate around much in the same way that they might in a Rumba or a Cha Cha. This usually occurs on the downbeat, when the weight is fully transferred to a step. The action of one bent/one straight leg causing the hip to tilt is the same as Rumba, except that in Samba, the leg you step onto is the bent leg.

That's a pretty rough overview, but it should give you an idea where to start. If it's not quite what you were looking for, feel free to ask a more specific question.

Sincerely,
Jonathan

Thanks so much, Jonathan. Very well explained. Should the diaphragm be in and the muscles very tight all the time? The Pros look so powerful in this dance !!!!
Thanks again for your time!