Investigation of models to estimate flight performance of gliding birds from wakes.

Mathematical models based on inviscid flow theory are effective at predicting the aerodynamic forces on large-scale aircraft. Avian flight, however, is characterized by smaller sizes, slower speeds, and increased influence of viscous effects associated with lower Reynolds numbers. Therefore, inviscid mathematical models of avian flight should be used with caution.

The functions of leg muscles, structures and mechanisms in running.

The actions of the major human leg muscles are well established; however, the functions of these muscle actions during steady running remain unclear. Here, leg structures and mechanisms are considered in terms of their functions in meeting the task of a vehicle acting as an effective machine, supporting body weight during translation with low mechanical work demand and in supplying mechanical work economically. Legs are modelled as a sequence of linkages that predict muscle actions and reveal the varying muscle functions within the integrated leg.

Dynamics of hinged wings in strong upward gusts.

A bird's wings are articulated to its body via highly mobile shoulder joints. The joints confer an impressive range of motion, enabling the wings to make broad, sweeping movements that can modulate quite dramatically the production of aerodynamic load. This is enormously useful in challenging flight environments, especially the gusty, turbulent layers of the lower atmosphere.

The collisional geometry of economical walking predicts human leg and foot segment proportions.

Human walking appears complicated, with many muscles and joints performing rapidly varying roles over the stride. However, the function of walking is simple: to support body weight as it translates economically. Here, a scenario is proposed for the sequence of joint and muscle actions that achieves this function, with the timing of muscle loading and unloading driven by simple changes in geometry over stance.

Legs as linkages: an alternative paradigm for the role of tendons and isometric muscles in facilitating economical gait.

Considerable attention has been given to the spring-like behaviour of stretching and recoiling tendons, and how this can reduce the work demanded from muscle for a given loss-return cycling of mechanical energy during high-speed locomotion. However, even completely isometric muscle-tendon units have the potential to act as tension struts, forming links in linkages that avoid the demand for mechanical work-cycling in the first place. Here, forelimb and hindlimb structures and geometries of quadrupeds are considered in terms of linkages that avoid mechanical work at the level of both the whole limb and the individual muscles.