Future directions for the analysis of musculoskeletal design and locomotor performance.

New techniques and conceptual frameworks offer new challenges and exciting opportunities for research on the biomechanics and physiology of vertebrate musculoskeletal design and locomotor performance. Past research based on electromyography and two-dimensional kinematics has greatly advanced the field of vertebrate functional morphology. Studies using these approaches have revealed much about vertebrate structure and function and have emphasized the importance of incorporating historical and developmental constraint and ecological context. Continued use of these experimental tools, but with greater emphasis on three-dimensional analysis of body movement, in combination with 3D kinetics and flow visualization of fluid movement past moving organisms, can now take advantage of the considerable advances in computing power and digital video technology. Indeed, surprisingly few detailed 3D analyses of movement for many locomotor modes and differing organisms are presently available. A challenge of 3D analyses will be to reduce the complexity of the data obtained in order to identify general principles of movement and biomechanics. New techniques and approaches for measuring muscle forces and length changes, together with activation patterns and movement, under dynamic conditions of more varied motor behavior are now also available. These provide the opportunity to study the mechanics and physiology of muscle function at greater depth and under more realistic conditions than has been previously possible. The importance of studying intact, behaving organisms under a broader range of locomotor conditions (other than steady state) and in the context of their natural environment remains a critical need for vertebrate biologists. This provides the much-needed opportunity for placing advances at more cellular and molecular levels into the context of whole organism function. Hence, studies at the organismal level remain paramount.