Jumping is an important locomotor behaviour used by many animals. The power required to perform a jump is supplied by skeletal muscle. The mechanical properties of skeletal muscle, including the power it can produce, are determined by its composition, which in turn reflects trade-offs between the differing tasks performed by the muscle. Recent studies suggest that muscles used for jumping are relatively fast compared with other limb muscles. As animals get bigger absolute jump performance tends to increase, but recent evidence suggests that adult jump performance may be relatively independent of body size. As body size increases the relative shortening velocity of muscle decreases, whereas normalised power output remains relatively constant. However, the relative shortening velocity of the fastest muscle fibre types appears to remain relatively constant over a large body size range of species. It appears likely that in many species during jumping, other factors are compensating for, or allowing for, uncoupling of jumping performance from size-related changes in the mechanical properties of muscle. In some species smaller absolute body size is compensated for by rapid development of locomotor morphology to attain high locomotor performance early in life. Smaller animal species also appear to rely more heavily on elastic storage mechanisms to amplify the power output available from skeletal muscle. Adaptations involving increased relative hindlimb length and relative mass of jumping muscles, and beneficial alteration of the origin and/or insertion of jumping muscles, have all been found to improve animal jump performance. However, further integrative studies are needed to provide conclusive evidence of which morphological and physiological adaptations are the most important in enhancing jump performance.