Biomedical subjects

P N Kugler

Publications and source records attributed to P N Kugler.

6 recordsLinked to original sources

PubMed1996

Adiabatic transformability hypothesis of human locomotion.

It is hypothesized that metabolic and mechanical changes in human locomotion associated with changes in speed v are constrained by two attractive strategies: Qmetab = 1 and delta Qmetab/delta v = a positive definite constant. Qmetab = delta Eks-1/ml O2s-1 where delta Eks-1 is the summed increments and decrements per unit time in the translational and rotational kinetic energies of the body's segments and ml O2s-1 is the rate at which chemical energy is dissipated. The expected constancy of delta Qmetab/delta v 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 Qmetab = 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 Qmetab < or = 1, with a nonlinear trajectory in v x Qmetab coordinates shaped by Qmetab = 1 (primarily) and the constancy of delta Qmetab/delta v. Running satisfied Qmetab > 1, with a linear trajectory in v x Qmetab coordinates conforming to delta Qmetab/delta v = a constant, with the constant predicted from invariants in the mechanical space v x delta Eks-1. Results also suggested that the metabolic costs of running might be predictable from measures made in the v x delta Eks-1 space.

Adult↗

PubMed1988

On the time allometry of co-ordinated rhythmic movements.

The focus is the power formulae relating periodic time in terrestrial locomotion and flight to mass and length. The periodic timing of limbs and wings oscillating comfortably in absolute co-ordination is viewed as the characteristic period tau 0 of a system in which the free, undamped oscillatory motion of a point mass m at a distance l from a fixed axis does work against two conservative forces. These forces are in the form of gravity g acting on the point mass and a spring of stiffness k acting at a distance b from the axis. The system's characteristic period can be expressed most simply as: tau 0 = 2 pi [ml2/(mlg + kb2)]1/2. In the biological instantiation of this hybrid mass-spring/simple pendulum system, muscular and other tissues function as the spring that elastically stores and releases mechanical energy. Regular oscillations are brought about and sustained by a muscular driving force that ordinarily is close to resonance. The resultant dynamical regime--basically, raising and lowering a mass at regular intervals with respect to gravity--is referred to as the pendular clocking mode of movement organization. The mode is investigated comfortably at a common period and a fixed phase. In absolute co-ordination, two wrist-pendulum systems can be interpreted physically as a virtual single system. The evidence suggests that the scalings of the periodic times of such systems to mass and to length follow directly from the dynamical properties inherent in the resonance equation of the pendular clocking mode. Recourse to biological constants to rationalize the time scale is unnecessary. Experiments on human wrist-pendular activity and detailed analyses of the mass and length dependencies of the locomotory cycle times of quadrupeds, large birds, small passerines, hummingbirds, and insects are performed with respect to the dynamical properties predicted for systems in the pendular clocking mode. The major conclusion is that all the time scales of terrestrial in locomotory time allometries follow systematically from differences in the length scale and differences in the relation of mass to length.

Animals↗

PubMed1986

Similarity principles and intrinsic geometries: contrasting approaches to interspecies scaling.

We criticize standard allometric approaches on the grounds that they emphasize scaling to one variable at a time, whereas chemically reactive hydrodynamic systems involved in pharmacokinetic phenomena are of higher dimension. We show that attempts based on mechanical similitude to set a dosage that would be equivalent across species (for example, from mouse to humans) lead to ambiguous results. Another failing of standard allometry may be its incapability to accommodate the neoteny of Homo sapiens, even though it helped discover the phenomenon. The retarded development in our species implied by neoteny can most clearly be seen in the evidence that both our brain size and our lifespan lie well above the allometric curve for Class Mammalia for these features. In contrast to allometry, which proposes a search for scaling coefficients through invariant external measurement reference frames, we propose a search for transformations of coordinate space coefficients in an intrinsic geometry for the mammalian body plan.

Aging↗

PubMed1986

Fluctuations and phase symmetry in coordinated rhythmic movements.

Pendular, clocking movements typify mammalian terrestrial locomotion. They can be investigated with a procedure in which people swing hand-held pendulums at the wrists, comfortably and rhythmically. Pendular, clocking behavior was examined for in-phase and out-of-phase coordinations. The periodic timing and powering of rhythmic movements in the comfort state follow from different laws (Kugler & Turvey, 1986). One law guides the assembling of the reference frame for "clocking." Another law guides the assembling of the muscular, escapement processes determining the cycle energy. Wing and Kristofferson's (1973) method for parsing periodic-timing variance into independent "clock" and "motor" sources was applied. Mean periodicity was unaffected by phase. "Clock" fluctuations, however, were larger out of phase than in phase. "Motor" fluctuations were indifferent to phase but reflected the departures of individual wrist-pendulum systems from their preferred periods. It appears that an intended phase relation is realized as a constraint on "clock" states. These states are more stable under the in-phase constraint than under the out-of-phase constraint.

Biophysical Phenomena↗

PubMed1984

A comment on equating information with symbol strings.

Symbol strings are advanced as the informational basis for many biological, physiological, and psychological phenomena. The role ascribed to them is that of indicating or directing states of affairs. Pattee has suggested that nature exploits information in this quasi-linguistic sense sparingly, that symbol strings are limited in detail, and that their relation to dynamics is one of complementation. A different, nonsymbolic view of information that addresses how animals can guide their locomotion in cluttered surroundings has been pursued by Gibson. It has considerable generality: information is low-dimensional qualitative properties of low-energy fields, lawfully generated by properties of systems and surround. It is argued that in the absence of information in Gibson's specificational sense, information in the indicational-injunctional sense is ineffective, and it is suggested that perplexities about the selective content of symbol strings may be resolved by a thoroughgoing understanding of Gibsonian information.

Animals↗

PubMed1981

Patterns of human interlimb coordination emerge from the properties of non-linear, limit cycle oscillatory processes: theory and data.

The present article represents an initial attempt to offer a principled solution to a fundamental problem of movement identified by Bernstein (1967), namely, how the degrees of freedom of the motor system are regulated. Conventional views of movement control focus on motor programs or closed-loop devices and have little or nothing to say on this matter. As an appropriate conceptual framework we offer Iberall and his colleagues' physical theory of homeokinetics first elaborated for movement by Kugler, Kelso, and Turvey (1980). Homeo kinetic theory characterizes biological systems as ensembles of non-linear, limit cycle oscillatory processes couple and mutually entrained at all the levels of organization. Patterns of interlimb coordination may be predicted from the properties of non-linear, limit cycle oscillators. In a set of experiments and formal demonstrations we show that cyclical, two-handed movements maintain fixed amplitude and frequency ( a stable limit cycle organization) under the following conditions: (a) when brief and constantly applied load perturbations are imposed on one hand or the other, (b) regardless of the presence or absence of fixed mechanical constraints, and (c) in the face of a range of external driving frequencies from a visual source. In addition, we observe a tight phasic relationship between the hands before and after perturbations (quantified by cross-correlation techniques), a tendency of one limb to entrain the other (mutual entrainment) and that limbs cycling at different frequencies reveal non-arbitrary, sub-harmonic relationships (small integer, subharmonic entrainment). In short, all the above patterns of interlimb coordination fall out of a non-linear oscillatory design. Discussion focuses on the compatibility of these results with past and present neurobiological work, and the theoretical insights into problems of movement offered by homeokinetic physics. Among these are, we think, the beginnings of a principled solution to the degrees of freedom problem, and the tentative claim that coordination and control are emergent consequences of dynamical interaction among non-linear, limit cycle oscillatory processes.

Journal Article↗