The lower limbs of five cadavers were dissected and the lengths of the muscle fibres and the weights of all the muscles below the knee were measured. From this information the relative strength and excursion of each muscle was determined. We found that the plantarflexors of the ankle were six times as strong as the dorsiflexors. We have therefore discarded the concept of "muscle balance" in tendon transfer surgery and propose that task appropriateness should be the guide. The constant relationship between muscle fibre length and muscle excursion means that contractures are accompanied by decreased excursion. Tendon lengthening improves deformity but does not improve the decreased active range of movement.