Energy of dance is interesting in that each individual brings his or her own interpretation to what fast, slow, sharp, smooth, tense or relaxed might be. It must be understood that certain movements will only look certain ways. No matter how hard or sharp one feels they’re swinging their arm in a circle it cannot be made to look sharp because the nature of the curve is smooth and continuous. Sharp energetic movements performed with speed would commonly cause excitement where as flowing movements combined with a slow tempo would have a calming effect. It is up to the choreographer to decide the energy level patterns of the dance but it is safe to say that a contrast of levels will create higher audience interest.
Have the class perform their phrases alternating energy levels. First perform phrase in slow motion as smoothly as possible. Second perform same phrase with tension. The same movements performed with different energy can evoke a completely different feeling in the audience. Another assignment will be to create a phrase where more than one energy level is occurring at once. The feet could be rapid fire steps while the torso and arms are floating smoothly through the space. Spanish dance is a good example of this.
Energy will give life to the dance and the lack of it will most assuredly cause its death. Each student will have his or her own energy level that movement feels comfortable. It’s up to the teacher to broaden the comfort level to allow for contrast.