Turn, turn turn: to everything there is a reason !

Swansea University researchers have made a ground breaking revelation that animal and human movement can result in substantial energy loss.

The team of researchers from Swansea University, the University of Roehampton, London and the Universidad Nacional del Comahue, Argentina have demonstrated in a paper published by Ecology Letters that animal and human turning has an energy cost which affects animal behaviour.

Turn Large Bird

The researchers in Biosciences, Computer Science, Sport Science and Engineering at Swansea University have demonstrated that birds such as condors which undertake regular and, at times, seemingly unpredictable changes of direction do so at a definite cost in terms of energy; such energy lost has to be regained by location of additional food resources or rising air, such as in thermals, to enable them to regain height.

In contrast to satellites that can orbit the Earth for extended periods in closed orbits without losing energy, animals on Earth have to change direction using friction forces or fluid drag forces to overcome the natural tendency to continue in a straight line.  Satellites move in the gravitational potential field of the Earth and are subject to what is known in physics as a ‘conservative’ force; in other words, the energy lost during a cycle is zero. For animals however, the inescapable conclusion is that they have to perform work to change direction through any desired angle or to move in a circular path or segment. This fact appears to have been overlooked by scientists since the earliest developments in mechanics by Galileo, Kepler and Newton.

Turn Footballer

‌Human sporting activities involving rapid changes in direction such as football, tennis etc will need to be re-examined for the impact on strategies and training.




Although it would appear to be apparent, demonstrating this facet of animal motion has been hindered by the more complex considerations required to model the motions of land-based animals, as well as fish , birds etc. The paper by Wilson et al in Ecology Letters reports theoretical models of bird flight as well as empirical evidence based on human turning motion and associated energy consumption, making the conclusions beyond doubt. This new result will affect many studies in biological systems as well as revolutionising sports science studies of all team sports where turning is involved, football being just one example.