Mechanics and energetics in running with special reference to efficiency
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Energetics
Energy cost
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ABSTRACT To interpret the movement strategies employed in locomotion, it is necessary to understand the source of metabolic cost. Muscles must consume metabolic energy to do work, but also must consume energy to generate force. The energy lost during steady locomotion and, hence, the amount of mechanical work muscles need to perform to replace it can be reduced and, in theory, even eliminated by elastically storing and returning some portion of this energy via the tendons. However, even if muscles do not need to perform any mechanical work, they still must generate sufficient force to tension tendons and support body weight. This study shows that the metabolic cost per hop of human hopping can largely be explained by the cost of producing force over the duration of a hop. Metabolic cost determined via oxygen consumption is compared with theoretical predictions made using a number of different cost functions that include terms for average muscle work, force, force rate and impulse (time integral of muscle force). Muscle impulse alone predicts metabolic cost per hop as well as more complex functions that include terms for muscle work, force and force rate, and explains a large portion (92%) of the variation in metabolic cost per hop. This is equivalent to 1/effective mechanical advantage, explaining a large portion (66%) of the variation in metabolic cost per time per unit body weight. This result contrasts with studies that suggest that muscle force rate or muscle force rate per time determines the metabolic cost per time of force production in other bouncing gaits such as running.
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ABSTRACT Previous studies have shown that large animals have systematically lower mass specific costs of locomotion than do smaller animals, in spite of there being no demonstrable difference between them in the mass-specific mechanical work of locomotion. Larger animals are somehow much more efficient at converting metabolic energy to mechanical work. The present study analyzes how this decoupling of work and cost might occur. The experimental design employs limb-loaded and back-loaded dogs and allows the energetic cost of locomotion to be partitioned between that used to move the center of mass (external work) and that used to move the limbs relative to the center of mass (internal work). These costs were measured in three dogs moving at four speeds. Increases in the cost of external work with speed parallel increases in the amount of external work based on data from previous studies. However, increases in the cost of internal work with speed are much less (<50 %) than the increase in internal work itself over the speeds examined. Furthermore, the cost of internal work increases linearly with speed, whereas internal work itself increases as a power function of speed. It is suggested that this decoupling results from an increase with speed in the extent to which the internal work of locomotion is powered by non-metabolic means, such as elastic strain energy and transfer of energy within and between body segments.
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Preface The Power of Nature - Energetics in Physical Geography Atmospheric Energetics Energetics of Erosion Rainfall, Runoff and Erosion of the Land: A Global View Energetics of Soil Processes Order and Truth: Energetics in Biogeography Conclusion Index.
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The purpose of this study is to elucidate the cost efficiency of mechanical energy of limited running and to provide theoretical bases of efficient running. Both cinematography and force measurement were conducted at the same time to the undergraduate students(male 20, female 18) by using four video came as and force platform to get force and kinematic data. By programming with a 7-segment model of body segment, maximum and minimum mechanical energy were obtained. By measuring the physiology energy cost of the same velocity on the treadmill, the mechanical cost efficiency was also obtained. The conclusions are as follows; 1. The correlation between maximum and minimum energy and body weight in men and women was low. The correlation between maximum and minimum energy and relative length of lower limb in men and women was significant(male : r=0.778, r=0.637, female : r =0.536, r=0.616 respectively). The correlation between maximum energy and height in women was significant(r=0.566). 2 The mechanical efficiency of real running in mechanical energy cost exists between maximum and minimum efficiency. 3. The correlation between the relative length of lower limb and the maximum cost efficiency in men and women was significant(r=0.698, r=0.683 respectively). The correlation between relative length of lower limb and minimum cost efficiency in men and women was also significant (r=0.738, r=0.724 respectively). Therefore, the man whose lower limb is relatively long shows high energy efficiency in motor performance.
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It is the similarity and difference in energetics in exercises that determines applying the training theory from one sport to others.Both similarity and difference exist in energetics of different exercises.The exponential correlation between relative oxygen contribution and du- ration of maximal exercise with involvement of large muscles is independent of exercise model, given the involved muscular of similar training level.Resulting from different involvement of muscular in exercises,the maximal lactate steady state varies in different exercises.Maximal lactate steady state,together with method of step test,should be considered when giving a fixed value to the lactate threshold.The introduction of energy cost made it possible to com- pare the efficiency of energy utilization between different exercises.Energy cost in different ex- ercises could provide energetic background for competitive sports and physical activities.
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This chapter contains sections titled: Introduction Anthropology and Energetics Basic Principles of Energetics Energy Expenditure Measurement of Energy Parameters Energetics and Human Evolutionary History Energetics and Adaptation among Contemporary Human Populations Energetics and Health Chapter Summary Acknowledgments References Cited Recommended Readings
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It has been proposed that the energy (heat + work) output of an isometric twitch is determined by the force that is generated under conditions of invariant activation, irrespective of muscle length. To test the effect of length and force on total energy output, muscles were stretched by increments beyond the muscle length at which twitch force is maximum (LO) and then stimulated; energy output and force then were measured. These data were compared with isovelocity twitches in which stimulated muscles, initially at different lengths, shortened (near maximum velocity) a constant distance and then redeveloped tension at lengths less than LO. If energy liberation was determined by force generation, plots of energy output versus force produced would be parallel with isovelocity twitches liberating extra energy as shortening heat. As predicted, the ratio of the slopes (n = 13) of these relations, 0.98 +/- 0.02, was not different from 1 and the shortening heat coefficient (alphaF/Pot, measured from the difference in intercepts), 0.15 +/- 0.01, was near to the expected value. Therefore, energy liberation in twitches appears to be uniquely determined by force generation and not by muscle length.
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