ISSN:
1432-0770
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Computer Science
,
Physics
Notes:
Abstract. It is hypothesized that metabolic and mechanical changes in human locomotion associated with changes in speed v are constrained by two attractive strategies: Q metab=1 and ΔQ metab/Δv=a positive definite constant. Q metab=ΔE k s-1/ml O2 s-1 where ΔE k s-1 is the summed increments and decrements per unit time in the translational and rotational kinetic energies of the body’s segments and ml O2 s-1 is the rate at which chemical energy is dissipated. The expected constancy of ΔQ metab/Δv was derived from an extension of Ehrenfest’s adiabatic hypothesis by which transformations (increases, decreases) in locomotion v can be considered as adiabatic, even though the biological conditions are nonconservative and non-rate-limited. The expected significance of Q metab=1 was derived from stability considerations of the symmetry per stride of stored and dissipated energy. An experimental evaluation was provided by collecting metabolic and mechanical measures on walking (10 subjects) and running (9 subjects) at progressively greater treadmill speeds but within the aerobic limit. Results revealed that walking was restricted to Q metab?1, with a nonlinear trajectory in v×Q metab coordinates shaped by Q metab=1 (primarily) and the constancy of ΔQ metab/Δv. Running satisfied Q metab〉1, with a linear trajectory in v×Q metab coordinates conforming to ΔQ metab/Δv=a constant, with the constant predicted from invariants in the mechanical space v×ΔE k s-1. Results also suggested that the metabolic costs of running might be predictable from measures made in the v×ΔE k s-1 space.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004220050223
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