Energetic consequences of mechanical loads

Loiselle, Denis S.; Crampin, EJ; Niederer, Steven A.; Smith, Nicholas P.; Barclay, Christopher John

doi:10.1016/j.pbiomolbio.2008.02.015

Cited by 20 publications

(5 citation statements)

References 66 publications

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“…In the spring‐loading model, the relative strength of adaptive thermogenesis is proportional to the decline in energy stores in a manner that can be analogized to Hooke's law which stipulates that the tension ( T ) on a spring is equal to the product of a constant ( k ) multiplied by the change in length of the spring ( x ). “ T ” in our body weight regulation experiments would be adaptive thermogenesis, “ k ” would vary between individuals but not be affected by the amount of weight lost, and “ x ” would be the amount of weight lost.…”

Section: Introductionmentioning

confidence: 99%

Models of energy homeostasis in response to maintenance of reduced body weight

Rosenbaum

Leibel

2016

Obesity

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Objective To test 3 proposed models for adaptive thermogenesis in compartments of energy expenditure following different degrees of weight loss. Specifically, 1.) There is no adaptive thermogenesis (constant relationship of energy expenditure (EE) to metabolic mass). 2.) There is a fixed degree of adaptive thermogenesis once fat stores are below a “threshold”. 3.) The degree of adaptive thermogenesis is proportional to weight loss. Methods The relationship between weight loss and EE was examined in seventeen weight stable in-patient subjects with obesity studied at usual weight and again following a 10% and a 20% weight loss. Results Following initial weight loss (10%), resting (REE) and non-resting (NREE) EE were significantly below those predicted on the basis of the amount and composition of weight lost. Further reductions below predicted values of NREE but not REE occurred following an additional 10% weight loss. Changes in body weight, composition, and/or energy stores were significantly correlated with changes in EE. Conclusion All models are applicable to the decline in EE following weight loss. The disproportionate decline in REE is consistent with a threshold model (no change with further weight loss) while the disproportionate decline in NREE is largely reflective of the degree of weight loss.

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Section: Introductionmentioning

confidence: 99%

Models of energy homeostasis in response to maintenance of reduced body weight

Rosenbaum

Leibel

2016

Obesity

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“…In other words, the operational hypothesis was that during lengthening (eccentric) contractions, muscles synthesize ATP, minimizing the energy cost relative to an isometric contraction (E=I−W?). For an outstanding review of this topic and its history, see Loiselle et al (2008).…”

Section: Introductionmentioning

confidence: 99%

Muscle force, work and cost: a novel technique to revisit the Fenn Effect

Ortega

Lindstedt

Nelson

et al. 2015

Journal of Experimental Biology

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Muscle produces force by forming cross-bridges, using energy released from ATP. While the magnitude and duration of force production primarily determine the energy requirement, nearly a century ago Fenn observed that muscle shortening or lengthening influenced energetic cost of contraction. When work is done by the muscle, the energy cost is increased and when work is done on the muscle the energy cost is reduced. However, the magnitude of the 'Fenn effect' and its mirror ('negative Fenn effect') have not been quantitatively resolved. We describe a new technique coupling magnetic resonance spectroscopy with an in vivo force clamp that can directly quantify the Fenn effect [E=I+W, energy liberated (E) equals the energy cost of isometric force production (I ) plus the work done (W )] and the negative Fenn effect (E=I−W ) for one muscle, the first dorsal interosseous (FDI). ATP cost was measured during a series of contractions, each of which occurred at a constant force and for a constant duration, thus constant force-time integral (FTI). In all subjects, as the FTI increased with load, there was a proportional linear increase in energy cost. In addition, the cost of producing force greatly increased when the muscle shortened, and was slightly reduced during lengthening contraction. These results, though limited to a single muscle, contraction velocity and muscle length change, do quantitatively support the Fenn effect. We speculate that they also suggest that an elastic element within the FDI muscle functions to preserve the force generated within the cross-bridges.

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“…Despite numerous experimental (see above) and theoretical (Gibbs & Chapman, 1985; Yasumura & Suga, 1988; Taylor et al 1993 a , b ; Landesberg & Sideman, 1999; Vendelin et al 2000) investigations, the cellular basis for the linear dependence of metabolic energy expenditure on PVA (3‐D case) or FLA (1‐D case) remains obscure (Loiselle et al 2008). However, Vendelin and co‐workers (2000) have proffered the following insight, which we paraphrase, as follows.…”

Section: Introductionmentioning

confidence: 99%

Myocardial twitch duration and the dependence of oxygen consumption on pressure–volume area: experiments and modelling

Han

Tran

Taberner

et al. 2012

The Journal of Physiology

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Key points• The energy expenditure of the heart is linearly related to its work performance, as measured by its development of pressure-volume area.• We have explored the basis of this phenomenon both experimentally (by measuring the heat production of isolated ventricular tissue undergoing cyclic contraction and relaxation) and theoretically (using mathematical modelling).• We provide the first evidence that the heat production of isolated trabeculae undergoing fixed-end contractions varies linearly with force-length area, and confirm that twitch duration increases progressively with muscle length.• Mathematical modelling reveals that length-dependent prolongation of the twitch reflects length-(or, equivalently, force-) dependent binding of Ca 2+ to troponin-C, together with Ca 2+ -dependent crossbridge cooperativity.• Mathematical modelling further reveals that the apparent linear dependence of heat production on force-length area is remarkably robust against departures from the linearity of length-dependent twitch duration.Abstract We tested the proposition that linear length dependence of twitch duration underlies the well-characterised linear dependence of oxygen consumption (V O 2 ) on pressure-volume area (PVA) in the heart. By way of experimental simplification, we reduced the problem from three dimensions to one by substituting cardiac trabeculae for the classically investigated whole-heart. This allowed adoption of stress-length area (SLA) as a surrogate for PVA, and heat as a proxy foṙ V O 2 . Heat and stress (force per cross-sectional area), at a range of muscle lengths and at both 1 mM and 2 mM [Ca 2+ ] o , were recorded from continuously superfused rat right-ventricular trabeculae undergoing fixed-end contractions. The heat-SLA relations of trabeculae (reported here, for the first time) are linear. Twitch duration increases monotonically (but not strictly linearly) with muscle length. We probed the cellular mechanisms of this phenomenon by determining: (i) the length dependence of the duration of the Ca 2+ transient, (ii) the length dependence of the rate of force redevelopment following a length impulse (an index of Ca 2+ binding to troponin-C), (iii) the effect on the simulated time course of the twitch of progressive deletion of lengthand Ca 2+ -dependent mechanisms of crossbridge cooperativity, using a detailed mathematical model of the crossbridge cycle, and (iv) the conditions required to achieve these multiple length dependencies, using a greatly simplified model of twitch mechano-energetics. From the results of these four independent investigations, we infer that the linearity of the heat-SLA relation (and, J.-C. Han and K. Tran contributed equally to this work.

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Energetic consequences of mechanical loads

Cited by 20 publications

References 66 publications

Models of energy homeostasis in response to maintenance of reduced body weight

Models of energy homeostasis in response to maintenance of reduced body weight

Muscle force, work and cost: a novel technique to revisit the Fenn Effect

Myocardial twitch duration and the dependence of oxygen consumption on pressure–volume area: experiments and modelling

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