Use is made of the guaranteed energy conservation property of any bond graph model (presuming that consistent energy variables are used). Thus power transformations are power conserving, and this property is exploited with respect to multiport transformers where many effort and flow variables may be involved. In these cases the relationship among the effort (flow) variables across the transformer may be easier to derive than the relationship among the flows (efforts). The power conserving nature of the transformer permits immediate derivation of the alternate variable relationship. This formulation procedure is applied to the reflex reaction of the arm.