Meeting Abstract
102.5 Thursday, Jan. 7 Explaining the 1/tc relation to locomotion cost in terms of constrained optimization or How metabolic cost rate can appear to both increase and decrease with time of force application GUTMANN, A.K.; BERTRAM, J.E.A.*; University of Calgary; University of Calgary annegutmann@gmail.com
Kram and Taylor (1990) hypothesized that ‘the rate of energy consumed by the muscles of a running animal per Newton of body weight is inversely proportional to the weight-specific rate of force application’. This implies that the weight-specific metabolic cost rate for running should be inversely proportional to contact time since, on average, an animal must produce a vertical ground reaction force equal to its body weight. And, indeed, this hypothesis fits nicely with data obtained from a wide variety of species running on a treadmill. But, if this hypothesis is based on general principles that are widely applicable to other types of locomotion, one would expect that it should also hold for hopping, especially since hopping and running appear to be mechanically similar activities. However, detailed metabolic data for human hopping show the opposite trend—metabolic cost decreases with decreasing contact time. How can such evidence be reconciled? In this talk we show how imposing constraints on locomotion (e.g. having animals run on a treadmill at fixed speeds) limits our observations to one small cross-section of the metabolic cost landscape, and how the apparent conflict between Kram and Taylor’s results and our hopping data can be resolved by evaluating a more complete cost function under certain constraint conditions.
