I don't know what 'bad' means myself - that' why I'm aksing. X: -My guesses: 1) Perhaps an inflexible chest cannot be extended the way dancers need it to be. (Thus leading to suboptimal posture). 2) Perhaps a heavy chest may pull the back & shoulders inwards. (hence - bad posture). 3) Perhaps a heavy chest taxes the upper-back muscles too much. (therefore - waste of energy, in order to keep proper posture). 4) Maybe it's just "bad" aesthetics. (like how I once heard that developed Trapezius aren't something one would like to see in dance). I don't understand what you mean. Would you please define 'functionality'? Is strength not functional? The first video looks like something I would not do without a professional guiding me. The second one has some nice exercises. (Sadly, not for the chest). But I have lost some flexibility, in the recent months, and you helped me decide to want to start doing Yoga.